Robust Multifunctional Yttrium-Based Metal-Organic Frameworks with Breathing Effect

Article

pubs.acs.org/IC

Robust Multifunctional Yttrium-Based Metal−Organic Frameworks

with Breathing Eﬀect

†

,‡

†

§

Ana D. G. Firmino, Ricardo F. Mendes, Margarida M. Antunes, Paula C. Barbosa,

,‡

Ser

́

gio M. F. Vilela,^†Anabela A. Valente, Filipe M. L. Figueiredo, Joao

P. C. Tome,

́^‡^,^∥

̃

,†

and Filipe A. Almeida Paz*

†

Department of Chemistry, CICECOAveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal

‡

Department of Chemistry, QOPNA, University of Aveiro, 3810-193 Aveiro, Portugal

§

Department of Materials & Ceramic Engineering, CICECO − Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro,

Portugal

∥

́

Centro de Química Estrutural, Instituto Superior Tecnico, University of Lisbon, Avenida Rovisco Pais, 1049-001 Lisbon, Portugal

*

S Supporting Information

ABSTRACT: Phosphonate- and yttrium-based metal−organic frameworks (MOFs), formulated

as [Y(H btp)]·5.5H O (1), [Y(H btp)]·2.5H O (2), (H O)[Y (H btp)(H btp)]·H O (3), and

5

2

5

2

3

2

5

4

2

[

Y(H btp)]·H O·0.5(MeOH) (4), were prepared using a “green” microwave-assisted synthesis

5 2

methodology which promoted the self-assembly of the tetraphosphonic organic linker [1,1′-

3+

biphenyl]-3,3′,5,5′-tetrayltetrakis(phosphonic acid) (H btp) with Y cations. This new family of

8

functional materials, isolated in bulk quantities, exhibits a remarkable breathing eﬀect. Structural

ﬂexibility was thoroughly studied by means of X-ray crystallography, thermogravimetry, variable-

temperature X-ray diﬀraction, and dehydration and rehydration processes, ultimately evidencing

a remarkable reversible single-crystal to single-crystal (SC−SC) transformation solely through

the loss and gain of crystallization solvent molecules. Topologically, frameworks remained

unaltered throughout this interconversion mechanism, with all compounds being binodal 6,6-

1

3

2

8 6

̈

connected network with a Schaﬂi symbol of {4 .6 }{4 .6 .8}. Results show that this is one of the

most stable and thermally robust families of tetraphosphonate-based MOFs synthesized reported

to date. Porous materials 2 and 3 were further studied to ascertain their performance as

heterogeneous catalysts and proton conductors, respectively, with outstanding results being registered for both materials.

Compound 2 showed a 94% conversion of benzaldehyde into (dimethoxymethyl)benzene after just 1 h of reaction, among the

best results registered to date for MOF materials. On the other hand, the protonic conductivity of compound 3 at 98% of relative

−2

−1

humidity (2.58 × 10 S cm ) was among the highest registered among MOFs, with the great advantage of the material to be

prepared using a simpler and sustainable synthesis methodology, as well as exhibiting a good stability at ambient conditions

(

temperature and humidity) over time when compared to others.

1

. INTRODUCTION

formations triggered by desorption and absorption of guest

molecules) may reach several Å in some cases. The term

The majority of published studies performed on solid-state

matter are associated with the innate rigidity and “quasi-

immobility” of compounds, with the exception of phase

“

breathing” is employed literally, i.e., associated with a very

small expansion and/or contraction movements with no bond

1

5

1

breaking between the two states. According to the

transitions occurring in the solid state. These “traditional”

6

classiﬁcation of framework robustness, MOFs which exhibit

ideas and preconceived notions used to describe solids have

been challenged, especially with the rise of porous coordination

polymers (PCPs) or metal−organic frameworks (MOFs) and

ﬂexible and dynamic structures with the ability to change their

channels or pores reversibly as a consequence of external

16

2

−5

stimuli constitute the third generation MOFs. It is, thus, of

great importance to study the structural response of a MOF to

its surrounding environment, in order to fully assess the extent

their exceptional properties.

Crystalline microporous solids

based on organic−inorganic counterparts that show dynamic

structural transformations triggered by external stimuli are

some of the examples that have recently received particular

interest, mainly because they retain topologies that are the same

as or similar to those of more rigid structures and, at the same

time, show important ﬂexibility. More commonly referred to

as the breathing eﬀect, these structural displacements caused

by temperature, pressure, chemical inclusion,

controlled molecular diﬀusion (reversible structure trans-

17,18

of potential applications of such materials.

There are a

considerable number of examples that have been reported

showing “breathing MOF” materials with two (or more) stable

19−21

6

,7

states as a function of adsorbed guests.

Due to this

8

9

10

11−13

or

Received: September 14, 2016

14

©

XXXX American Chemical Society

A

DOI: 10.1021/acs.inorgchem.6b02199

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

behavior, these materials have been proposed for applications

that value the ability of controlling pore size according to the

variation of pressure, concentration of guest molecules, and/or

other external stimuli. The selective adsorption of gases or

mixtures of gases is an obvious application for breathing MOFs

as well as chemical sensing and adsorption of hazardous

mortar with 200 mg of KBr) using a Bruker Tensor 27 spectrometer

by averaging 256 scans at a maximum resolution of 2 cm .

−1

Elemental analyses for C and H were performed with a Truspec

Micro CHNS 630-200-200 elemental analyzer at the Department of

Chemistry, University of Aveiro. Analysis parameters: sample amount

between 1 and 2 mg; combustion furnace temperature = 1075 °C;

afterburner temperature = 850 °C. Detection method: carbon and

hydrogen, infrared absorption. Analysis time = 4 min. Required gases:

carrier, helium; combustion, oxygen; pneumatic, compressed air.

Routine powder X-ray diﬀraction (PXRD) data for all prepared

materials were collected at ambient temperature on an Empyrean

1

5

waste.

In this work, and following our previously reported studies

with the novel [1,1′-biphenyl]-3,3′,5,5′-tetrayltetrakis-

(

phosphonic acid) (H btp) organic linker, a highly symmetric

8

ligand bearing four phosphonic acid groups in a biphenyl

backbone, we report the preparation of a new family of

breathing materials formulated as [Y(H btp)]·5.5H O (1),

PANalytical diﬀractometer (Cu Kα1,2 X-radiation, λ

1.544426 Å), equipped with a PIXcel 1D detector and a ﬂat-plate

sample holder in a Bragg−Brentano para-focusing optics conﬁguration

45 kV, 40 mA). Intensity data were collected by the step-counting

1

= 1.540598 Å, λ

2

=

5

2

(

[

Y(H btp)]·2.5H O (2), (H O)[Y (H btp)(H btp)]·H O (3),

5 2 3 2 5 4 2

method (step 0.01°), in continuous mode, in the ca. 3.5 ≤ 2θ° ≤ 50°

and [Y(H btp)]·H O·0.5(MeOH) (4). H btp was successfully

5

2

8

range.

used for the self-assembly of these microporous multifunctional

materials using a microwave-assisted methodology, a simple

and fast approach that led to high yields of phase-pure

compounds. The crystal structure of all frameworks was

unveiled by single-crystal X-ray diﬀraction, and right from the

start a single-crystal to single-crystal (SC−SC) relationship

between networks was identiﬁed. Not all oxygen atoms of the

phosphonate ligand participate in coordination bonds, con-

tributing to intermolecular interactions with uncoordinated

water molecules that are present in the pores. Solvent

adsorption/desorption triggered single-crystal to single-crystal

phase transformations in this family of materials, and even

though a handful of examples of SC−SC transformations have

already been reported regarding phosphonate-based

1_H_a_n_d₃₁_P_M_A_S_s_p_e_c_t_r_a_w_e_r_e_r_e_c_o_r_d_e_d_a_t₉_.₄_T_o_n_a_B_r_u_k_e_r_A_v_a_n_c_e

4

00 wide-bore spectrometer (DSX model) on a 4 mm BL cross-

polarization magic-angle spinning (CPMAS) VTN probe at 161.9

MHz. For the ³¹P HPDEC spectra, a 90° single pulse excitation of 3.0

μs was employed; recycle delay: 60 s; ν = 12 kHz. Chemical shifts are

R

quoted in parts per million (ppm) with respect to an 85% H PO

3

4

solution.

¹H nuclear magnetic resonance (NMR) spectra were recorded with

a Bruker AVANCE 300 spectrometer at 300.13 MHz. Deuterated

chloroform (CDCl ) was used as solvent, and tetramethylsilane or

3

H PO (85%) was employed as internal reference. Chemical shifts (δ)

3

4

are quoted in ppm and the coupling constants (J) in Hz.

.2. Reagents and Solvents. Chemicals, including solvents, were

readily available from commercial sources and were used as received

2

without further puriﬁcation: yttrium(III) chloride hexahydrate (YCl

·

3

7

,19,22−27

MOFs,

in this work, we veriﬁed that this structural

6H O, 99.9%, Sigma-Aldrich); copper(II) chloride dihydrate (CuCl

2

H O, extra pure, Riedel); 3,5-dibromophenylboronic acid

2

elucidation technique allowed us to predict the probable good

behavior of the synthesized materials as proton conductors: (i)

the hydrophilic trait of phosphonate groups that easily establish

hydrogen bonds, (ii) the amount of adsorbed water molecules

that would act as proton-conducting media within the channels

of the frameworks, and (iii) the crystalline proton-conducting

pathways identiﬁed along the channels that have given useful

information for understanding the proton dynamics in the

materials. These important features allied with the relatively

high thermal and mechanical stability (due to the presence of

inorganic clusters that create the framework solid basis,

(

C H BBr O , containing varying amounts of anhydride, TCI); 1,10-

6 5 2 2

phenanthroline monohydrate (C H N O, >99.0%, TCI); sodium

12

10

2

hydroxide (NaOH, ≥98%, Sigma-Aldrich); triethyl phosphite

(

C H PO , 98%, Sigma-Aldrich); tetrakis(triphenylphosphine)-

2

5

3

palladium(0) (Pd[(C H ) P] , 99%, Sigma-Aldrich); styrene oxide

6

5

3

4

(

C H O, purum ≥97%, Fluka); benzaldehyde (C H O, 99%, Sigma-

8

7

6

Aldrich); hydrochloric acid (HCl, 37%, Jose

Santos Lta.); dichloromethane (CH Cl , pure, Sigma-Aldrich);

́

Manuel Gomes dos

2

methanol (CH

99.9%, Sigma-Aldrich); n-hexane (C H , >99%, Sigma-Aldrich);

O, >99.8%, Fluka or Chromasolv for HPLC,

4

≥

6

14

propan-2-ol (C H O, 99,7%, Carlo Erba Reagents); deuterated

3

8

dimethyl sulfoxide (DMSO-d , 99,99%, Euriso-top); deuterated

6

together with the C−PO bond that also promotes stability

3

chloroform (CDCl , 99,99%, Euriso-top); potassium bromide (KBr

3

at high temperatures) render these phosphonate-based MOFs

as an interesting family of compounds. The performance of

material 2 as heterogeneous acid catalyst and the protonic

conductivity of compound 3 were evaluated and compared with

analogous materials available in the literature.

for infrared spectroscopy, >99%, BDH SpectrosoL).

2

.3. Synthesis of [1,1′-Biphenyl-3,3′,5,5′-tetrayltetrakis-

(

phosphonic acid) (H btp). [1,1′-Biphenyl-3,3′,5,5′-tetrayltetrakis-

8

(phosphonic acid) (H btp) was prepared by a three-step reaction

8

sequence according to published procedures with small modiﬁcations

2

8,29

(

Scheme 1).

A solution of [{(phen)Cu(μ-OH)} C·3H O (cat-1, 0.0231 g,

2

2. EXPERIMENTAL SECTION

0

.0358 mmol) and 3,5-dibromophenylboronic acid (0.500 g, 0.179

2

.1. General Instrumentation. SEM (scanning electron micros-

mmol) in propan-2-ol (5 mL) was stirred at ambient temperature

overnight in air. The resulting gray mixture was monitored by TLC (n-

hexane), and once the reaction was complete, the mixture was

concentrated in vacuo. The residue was puriﬁed by silica gel column

ﬂash chromatography (n-hexane) to aﬀord 3,3′,5,5′-tetrabromobi-

copy) images were acquired using either a Hitachi S4100 ﬁeld

emission gun tungsten ﬁlament instrument working at 25 kV or a high-

resolution Hitachi SU-70 working at 4 kV. Samples were prepared by

deposition on aluminum sample holders followed by carbon coating

using an Emitech K950X carbon evaporator. EDS (energy dispersive

X-ray spectroscopy) data and SEM mapping images were recorded

using the latter microscope working at 15 kV and using either a Bruker

Quantax 400 or an Esprit 1.9 EDS microanalysis system.

phenyl (L′) (0.325 g, 77%) as a white solid.

1

L′: H NMR (300.13 MHz, CDCl ) δ (in ppm) 7.60 (d, J = 3.0 Hz,

3

4 H, H2, 2′, 6 and 6′) and 7.70 (t, J = 3 Hz, 2 H, H4 and 4′).

After the synthesis of L′, [1,1′-biphenyl]-3,3′,5,5′-tetrayltetrakis-

Thermogravimetric analyses (TGA) were carried out using a

Shimadzu TGA 50, from ambient temperature to ca. 800 °C (heating

rate of 5 °C/min), under a continuous stream of air at a ﬂow rate of 20

(phosphonic acid) (H btp) was prepared following our previously

8

2

9,38

published procedure.

2.4. Microwave-Assisted Synthesis of MOFs. 2.4.1. [Y(H btp)]·

5

−1

mL min .

5.5H O (1). A reactive mixture composed of 0.025 g of [1,1′-

2

Fourier transform infrared (FT-IR) spectra (in the range 4000−350

biphenyl]-3,3′,5,5′-tetrayltetrakis(phosphonic acid) (H btp) and 0.016

8

−

1

cm ) were recorded as KBr pellets (2 mg of sample was mixed in a

g of YCl ·6H O, with an overall molar ratio of approximately 1:1

3

2

B

DOI: 10.1021/acs.inorgchem.6b02199

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

2

.4.6. Thermogravimetric Analysis (TGA) Data (Weight Losses in

Scheme 1. Simpliﬁed Three-Step Synthetic Procedure To

Prepare the Tetrapodal [1,1′-Biphenyl]-3,3′,5,5′-

%

) and Derivative Thermogravimetric Peaks (DTG, in Italics Inside

a

the Parentheses). 22−190 °C −3.24% (135 °C); 190−255 °C

1.68% (240 °C); 255−350 °C −1.73% (282 °C). Total loss: 6.7%.

tetrayltetrakis(phosphonic acid) (H btp) Organic Linker

8

−

−1

+

2

.4.7. Selected FT-IR Data (in cm ; from KBr Pellets). ν(H O ) =

3

505 s; ν(H O ) = 3375 m; ν(POH) = 3250 m; ν(C−H) = 3075 m;

2

cryst

ν(CC) + δ(H O) = 1810−1575 m; δ(P−C) = 1420−1370 m;

2

ν(PO) = 1280−1120 m-vs; ν(P−O) = 1120−860 vs; ν(P−C) =

6

96 m.

2

.4.8. [Y(H btp)]·H O·0.5(MeOH) (4). 0.025 g of (H O)[Y (H btp)-

5 2 3 2 5

(

H btp)]·H O (3) was placed in a round-bottom ﬂask with 1 mL of

4 2

methanol. The mixture was vigorously stirred during 1 h at ambient

temperature. The resulting [Y(H btp)]·H O·0.5(MeOH) (4) com-

5

2

pound was recovered by vacuum ﬁltration as a white powder and then

air-dried at ambient temperature.

Elemental CH composition (%): calcd C 25.3, H 2.55; found C

2

4.7, H 2.02.

.4.9. Thermogravimetric Analysis (TGA) Data (Weight Losses in

) and Derivative Thermogravimetric Peaks (DTG, in Italics Inside

2

%

the Parentheses). 23−70 °C −2.57% (57 °C); 70−190 °C −2.81%

(

140 °C); 190−255 °C −1.52% (242 °C); 255−350 °C −1.77% (290

°

C). Total loss: 8.7%.

−1

2

.4.10. Selected FT-IR Data (in cm ; from KBr Pellets). ν(H O

2 cryst

+

POH) = 3600−2670 br; ν(CC) + δ(H O) = 1705−1580 m;

2

δ(P−C) = 1420−1365 m; ν(PO) = 1265−1120 vs; ν(P−O) =

1

120−870 vs; ν(P−C) = 697 m.

.5. Single-Crystal X-ray Diﬀraction Studies. Inspection of

2

various batches of the microcrystalline powder isolated from

microwave trials was performed using a Stemi 2000 stereomicroscope

equipped with Carl Zeiss lenses. This allowed the identiﬁcation of

abundant and long white needles [dimensions of about 0.08 × 0.01 ×

a

cat-1 = [{(phen)Cu(μ-OH)} Cl ]·3H O.

2

0

.01 mm for [Y(H btp)]·5.5H O (1), 0.08 × 0.02 × 0.01 mm for

5 2

[

Y(H btp)]·2.5H O (2), and 0.16 × 0.03 × 0.03 mm for (H O)-

3

+

5

2

3

(

H btp: Y ), was dissolved at ambient temperature in a mixture of

8

Y (H btp)(H btp)]·H O (3)], which were studied using single-

2

5

4

2

distilled water, HCl (6 M) and methanol (2 mL of each solvent), and

placed inside a 10 mL IntelliVent microwave reactor. The reaction

took place inside a CEM Focused Microwave Synthesis System

Discover S-Class equipment, under constant magnetic stirring

crystal X-ray diﬀraction. Needles were manually selected and harvested

from the batch solution and immersed in highly viscous FOMBLIN Y

perﬂuoropolyether vacuum oil (LVAC 140/13, Sigma-Aldrich) to

30

avoid degradation caused by the evaporation of the solvent. Crystals

(

3

controlled by the microwave equipment), at 100 °C for 60 min

were then mounted on a Hampton Research CryoLoops, and

preliminary X-ray diﬀraction data were collected at 180(2) K on a

Bruker D8 QUEST equipped with Mo Kα sealed tube (λ = 0.71073

Å), a multilayer TRIUMPH X-ray mirror, a PHOTON 100 CMOS

detector, and an Oxford Instruments Cryostrem 700+ series low

temperature device. The instrument was controlled with the APEX2

using an irradiation power of 50 W). A constant ﬂow of air (ca. 20−

0 psi of pressure) ensured a close control of the temperature inside

the reactor. The resulting product, [Y(H btp)]·5.5H O (1), was

5

2

isolated as a white microcrystalline powder in suspension. Recovery by

vacuum ﬁltration was not possible since the material was only stable in

the mother liquor.

31

software package.

The optimal synthetic conditions (100 °C; 60 min) were found by

systematically varying the microwave parameters such as temperature

40, 60, 80, 100, and 135 °C) and irradiation time (1, 5, 15, 30, and 60

min). The irradiation power was maintained constant at 50 W.

.4.2. [Y(H btp)]·2.5H O (2). This material was obtained after

ﬁltration of [Y(H btp)]·5.5H O (1) under reduced pressure. The

white powder was washed with copious amounts of distilled water and

then air-dried at ambient temperature.

Diﬀraction images were processed using the software package

3

2

SAINT+, and data were corrected for absorption by the multiscan

semiempirical method implemented in SADABS. The crystal

structures of compounds 1−3 were solved using the algorithm

implemented in SHELXT-2014,

location of almost all of the heaviest atoms composing the asymmetric

units of the three materials.

Hydrogen atoms bound to carbon were placed, for all compounds,

at their idealized positions using the HFIX 43 instruction in SHELXL-

2

(

3

2

5

2

34,35

which allowed the immediate

5

2

Elemental CH composition (%): calcd C 23.8, H 2.67; found C

2

3.9, H 2.70.

.4.3. Thermogravimetric Analysis (TGA) Data (Weight Losses in

) and Derivative Thermogravimetric Peaks (DTG, in Italics Inside

014. These hydrogen atoms were included in subsequent reﬁnement

2

cycles with isotropic thermal displacements parameters (U ) ﬁxed at

%

iso

the Parentheses). 28−100 °C −4.51% (59 °C); 100−144 °C −1.52%

1.2Ueq of the parent carbon atoms. The hydrogen atoms associated

with water molecules could not be located from diﬀerence Fourier

maps, and no attempts were made to place them in calculated

positions for 1 and 2. These atoms were, however, included in the

empirical formula of the compounds (Table 1). For one of the water

molecules in 2 and the hydronium cation in 3 the hydrogen atoms

were markedly visible in diﬀerence Fourier maps and were included in

subsequent reﬁnement cycles with isotropic thermal displacements

parameters (Uiso) ﬁxed at 1.5Ueq of the parent atoms, and with ﬁxed

O−H and H···H distances of 0.95(1) and 1.55(1) Å, respectively.

Hydrogen atoms associated with the terminal −POH groups were

placed taking into account the environment of the terminal oxygen

atom and the P−O distances (i) in calculated positions using the

HFIX 147 instruction for compounds 1 and 2 and (ii) located from

(

°

131 °C); 144−250 °C −1.47% (235 °C); 250−310 °C −1.35% (293

C); 310−350 °C −1.36% (332 °C). Total loss: 10.2%.

−1

2

.4.4. Selected FT-IR Data (in cm ; from KBr Pellets). ν(H O

+

cryst

2

POH + C−H) = 3600−2650 br; ν(CC) + δ(H O) = 1860−1560

2

m; δ(P−C) = 1420−1365 m; ν(PO) = 1265−1120 vs; ν(P−O) =

1

120−860 vs; ν(P−C) = 697 m.

2

.4.5. (H O)[Y (H btp)(H btp)]·H O (3). This material was obtained

3 2 5 4 2

from the dehydration of [Y(H btp)]·2.5H O (2). Compound 2 (0.025

g) was placed into an open crucible inside an oven, preheated at 110

C, and dehydrated overnight. The resulting white powder was

recovered and cooled to ambient temperature.

Elemental CH composition (%): calcd C 24.9, H 2.27; found C

5

2

°

2

4.9, H 2.27.

C

DOI: 10.1021/acs.inorgchem.6b02199

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

Crystallographic data (including structure factors) for the crystal

structures of compounds 1, 2, and 3 have been deposited with the

Cambridge Crystallographic Data Centre as supplementary publication

data Nos. CCDC 1496868−1496870. Copies of the data can be

obtained free of charge on application to CCDC, 12 Union Road,

Cambridge CB2 2EZ, U.K. FAX: (+44) 1223 336033. E-mail:

deposit@ccdc.cam.ac.uk .

Table 1. Crystal Data Collection and Structure Reﬁnement

Details for [Y(H btp)]·5.5H O (1), [Y(H btp)]·2.5H O (2),

5

2

5

2

and (H O)[Y (H btp)(H btp)]·H O (3)

3

2

5

4

2

1

2

3

formula

C H O P Y

12 13 13 4

2

4

44 35

8

2

24 32 29

8

2

formula wt

temp/K

cryst syst

space group

a/Å

1318.17

180(2)

1210.07

578.01

2.6. Variable-Temperature Powder X-ray Diﬀraction. Varia-

180(2)

100(2)

triclinic

ble-temperature powder X-ray diﬀraction data were collected on a

monoclinic

PANalytical X’Pert Powder diﬀractometer (Cu Kα₁_,₂X-radiation, λ =

1

P2 /n

1

P2 /c

1

P1

̅

1

.540598 Å, λ = 1.544426 Å) under an air atmosphere, equipped with

2

9.3435(11)

22.187(3)

9.2274(9)

23.952(2)

9.2453(7)

10.0930(8)

11.7780(9)

97.803(3)

104.205(4)

111.348(4)

961.00(13)

2

a PIXcel 1D detector, a ﬂat-plate sample holder in a Bragg−Brentano

para-focusing optics conﬁguration (40 kV, 50 mA), and a high-

temperature Anton Paar HKL 16 chamber controlled by an Anton

Paar 100 TCU unit. Intensity data were collected in the continuous

mode (ca. 100 s data acquisition) in the angular range ca. 5 ≤ 2θ° ≤

35.

b/Å

c/Å

13.8761(17)

90

10.4430(10)

α/deg

90

β/deg

109.571(4)

90

114.979(3)°.

90

γ/deg

volume/Å³

2710.3(6)

2

2092.2(4)

2

2.7. Heterogeneous Catalysis. A 5 mL borosilicate batch reactor,

equipped with a magnetic stirrer (800 rpm) and a valve for sampling,

was charged with 1.5 mL of methanol, 0.4 M substrate, and the MOF

Z

ρ_c_a_l_c/g cm⁻

3

1.615

1.921

1.998

−1

_μ₍_M_o_K_α₎_/_m_m₋1

catalyst (3.3 or 20 g_M_O_FL ). Substrates were styrene oxide and

benzaldehyde. The catalytic performance of [Y(H btp)]·2.5H O (2)

2.459

3.166

3.436

cryst type

colorless needle colorless needle colorless needle

5

2

−1

(

³^.³^gMOF L ) was compared to that of the ligand and metal

cryst size/mm

0.08 × 0.01 ×

.01

0.08 × 0.02 ×

0.01

0.16 × 0.03 ×

0.03

0

precursors, namely, H btp and YCl ·6H O, respectively (5.7 mM,

8

3

2

corresponding to a molar amount equivalent to the amount of ligand

θ range/deg

2.316−25.342

−11 ≤ h ≤ 11

3.528−29.128

−12 ≤ h ≤ 12

−32 ≤ k ≤ 32

−14 ≤ l ≤ 13

53036

3.545−29.131

−12 ≤ h ≤ 12

−13 ≤ k ≤ 13

−16 ≤ l ≤ 16

45517

−

1

^o^r^m^e^t^a^l^a^d^d^e^d^t^o^g^e^t^h^e^r^wⁱ^t^h^a^M^O^F^l^o^a^dⁱⁿ^g^o^f³^.³^gMOF L ).

Reactions were carried out under atmospheric conditions, and the

batch reactors were immersed in a thermostated oil bath at 35 °C.

A leaching test was also carried out for the MOF catalyst. The

experiment consisted of carrying out the reaction of styrene oxide (0.4

index ranges

−

26 ≤ k ≤ 26

16 ≤ l ≤ 16

collected reﬂns

indep reﬂns

34782

⁴⁹⁶²⁽^Rint

=

⁵⁶³¹⁽^Rint

0.1348)

=

⁵¹⁵²⁽^Rint

0.0472)

=

−1

^M⁾^wⁱ^t^h^m^e^t^h^aⁿ^o^lⁱⁿ^t^h^e^p^r^e^s^eⁿ^c^e^o^f²⁽³^.³^gMOF L ) at 35 °C, during

0

.0579)

3

0 min. Afterward, the solid was separated from the liquid phase using

completeness (to

θ = 25.24°) (%)

100.0

99.7

a 0.20 μm PTFE membrane ﬁlter. The obtained ﬁltrate was transferred

to a preheated (35 °C) batch reactor and left to react at the same

temperature under magnetic stirring.

The recyclability of the MOF catalyst was studied by carrying out

consecutive batch runs (benzaldehyde as substrate). Between runs the

solid catalyst was separated from the reaction mixture by

centrifugation (3500 rpm), washed with methanol, and dried under

air overnight.

ﬁnal R indices [I > R1 = 0.0630

R1 = 0.0640

wR2 = 0.0969

R1 = 0.1227

wR2 = 0.1141

R1 = 0.0278

wR2 = 0.0634

R1 = 0.0357

wR2 = 0.0662

2σ(I)]

wR2 = 0.1713

R1 = 0.0918

wR2 = 0.1911

ﬁnal R indices (all

data)

largest diﬀ peak and 1.507 and

1.511 and

−0.863

0.568 and

−

3

hole/e Å

−1.067

−0.399

a

b

2

2 2

R1 = ∑||F | − |F ||/∑|F |. wR2 = {∑[w(F − F ) ]/

o

c

o

c

2

1/2

c

2

The progress of the catalytic reactions was monitored using a Varian

∑

2

[w(F ) ]} . w = 1/[σ (F ) + (mP) + nP] where P = (F

+

o

3

0

800 GC equipped with a capillary column (Bruker, BR-5, 30 m ×

2

F )/3.

c

.25 mm × 0.25 μm) and a ﬂame ionization detector, and H was the

2

carrier gas. Reaction products were identiﬁed using a GC−MS (Trace

GC 2000 series (Thermo Quest CE Instruments), DSQ II (Thermo

Scientiﬁc)), equipped with a capillary column (DB-1 MS, 30 m × 0.25

mm × 0.25 μm), using He as carrier gas.

diﬀerence Fourier maps and ﬁxed with a distance of 0.95(1) Å in the

case of compound 3. All these atoms were included in subsequent

reﬁnement cycles with isotropic thermal displacements parameters

2.8. Proton Conductivity. The proton conductivity (σ) of

(

U ) ﬁxed at 1.5U of the parent atoms. One phosphonic acid group

P2) was found to be disordered in compound 1. All atoms involved in

iso eq

pelletized samples was determined by electrochemical impedance

spectroscopy. Disk shaped samples were obtained after pressing the

powders in a uniaxial press at 6.25 MPa, and then isostatically at 200

MPa. The apparent density of these pellets was obtained from

measuring their weight and the geometric dimensions. Silver

electrodes were applied on both sides of the pellets by painting a

commercial paste (Agar Scientiﬁc). Samples were placed on ceramic

tubular sample-holders inside a climatic chamber (ACS DY110) in

order to carry out the measurements under variable temperature (40−

this structural disorder were found from diﬀerence Fourier maps, and

no restrictions in distances and angles were included during the

reﬁnement stages. The occupancy rates were ﬁxed at 40 and 60% for

each phosphonic acid group.

The last diﬀerence Fourier map synthesis showed the highest peak

−3

(

0

(

1.51 e Å ) and the deepest hole (−1.07 e Å ) located at 0.87 and

.17 Å from P4′ and O3W, respectively, for 1. For 2 the highest peak

−

3

−3

1.51 e Å ) and the deepest hole (−0.86 e Å ) are located at 0.84

9

4 °C) and relative humidity (RH, 20−98%). One of the pellets, noted

as predried, was subjected to a premeasurement thermal treatment at

20 °C overnight. The current collection was ensured by means of

and 0.22 Å from Y1 and O11, respectively. For 3 the highest peak

−3

(

0.57 e Å ) and the deepest hole (−0.40 e Å ) were located at 0.83

1

and 0.27 Å from P3 and H3, respectively.

platinum wires. The impedance spectra were collected between 20 Hz

and 2 MHz with test signal amplitude of 100 mV using an Agilent

E4980A LCR meter, and subsequently analyzed with ZView (Version

2.6b, 1990−2002, Scribner Associates). The ohmic resistance (R) of

the pellets was normalized to the geometry of the samples in order to

All structural reﬁnements were performed using the graphical

36

interface ShelXle. Structural drawings have been created using the

37

software package Crystal Impact Diamond. Information concerning

crystallographic data collection and structure reﬁnement details is

summarized in Table 1. Tables S1 and S2 gather the most signiﬁcant

geometrical parameters of the crystallographically independent Y³

coordination spheres for all compounds and the hydrogen bond

interactions.

+

−1

calculate the conductivity through the usual formula σ = L(RA) ,

where L is the thickness of the pellets and A is the surface area of the

electrodes.

D

DOI: 10.1021/acs.inorgchem.6b02199

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

. RESULTS AND DISCUSSION

.1. Ligand Synthesis Strategy. Following our previous

Article

3

tandem to further evaluate phase purity and homogeneity of the

bulk materials.

3

incursions using di- and triphosphonic linkers, we hypothesized

that the inclusion of additional aromatic rings and phosphonic

acid chelating groups should enhance structural robustness and

connectivity, ultimately leading to more structurally and

topologically interesting features. On the other hand, the

increase in the number of phosphonic acid groups should

predictably also enhance the properties of the networks toward

future applications, i.e., an expected signiﬁcant improvement in

38

the catalytic activity and also in the ability to conduct protons.

[

1,1′-Biphenyl-3,3′,5,5′-tetrayltetrakis(phosphonic acid)

(

H btp) was prepared using a MWAS methodology previously

8

2

9,38

published by us.

In this work we decided to extend the

synthesis route to the L′ ligand precursor, because its

preparation is, in this way, much less expensive than buying

from commercial suppliers. Therefore, a novel three-step

procedure was developed: the preparation starts with a

homocoupling reaction to synthesize the biphenyl backbone

of the molecule, followed by the palladium-catalyzed cross-

coupling reaction using triethyl phosphite to prepare the

corresponding dialkyl arylphosphonate. A hydrolysis reaction

was performed using hydrochloric acid to isolate the ﬁnal

polyphosphonic acid (Scheme 1).

1

Figure 1. H MAS spectrum of [Y(H btp)]·2.5H O (2) and

5

2

(H

O)[Y (H btp)(H btp)]·H O (3). Spinning sidebands are denoted

2 5 4 2

using an asterisk.

3

Adding a third step for the ligand synthesis procedure

represented a great advantage because the costs with ligand

synthesis could be signiﬁcantly reduced, without compromising

extensively the global synthesis yield of the ﬁnal molecule (ca.

3

.3. Structural Elucidation. Compounds [Y(H btp)]·

5

2 3 2 5 4 2

2

.5H O) (2) and (H O)[Y (H btp)(H btp)]·H O) (3) were

obtained by single-crystal to single-crystal (SC−SC) trans-

formations, with structural transformations being accompanied

by single-crystal X-ray diﬀraction data. As we compare the

empirical formulas of all compounds ([Y(H btp)]·5.5H O (1),

9

0%). H btp, 3,3′,5,5′-tetrabromobiphenyl (L′), and octaethyl

8

[

1,1′-biphenyl]-3,3′,5,5′-tetrayltetrakis(phosphonate) (L″)

5

2

were all characterized by NMR spectroscopy (see Experimental

Section and Figure S1 for further details).

[

(

Y(H btp)]·2.5H O (2), and (H O)[Y (H btp)(H btp)]·H O

3)) we can immediately infer that the level of protonation and

the type of ligand-to-metal coordination is almost the same for

all materials. The main diﬀerence lies in the crystallization water

molecules which are gradually removed (5.5 in 1, 2.5 in 2, and 2

5 2 3 2 5 4 2

3

.2. Preparation of MOFs. Reaction between [1,1′-

biphenyl]-3,3′,5,5′-tetrayltetrakis(phosphonic acid) (H btp)

and yttrium(III) chloride hydrate aﬀorded a new family of

8

structures, [Y(H btp)]·5.5H O (1), [Y(H btp)]·2.5H O (2),

+

5

2

5

2

in 3), and the presence of a H O cation in 3 (formed in situ

3

and (H O)[Y (H btp)(H btp)]·H O (3), possessing a remark-

3

2

5

4

2

most likely due to proton transfer from a neighboring

phosphonic acid group). These SC−SC transformations

occur solely by removal of water molecules, without any

break or formation of new covalent bonds. The similarity of

these three structures can be veriﬁed in a topological analysis,

which allows us to reduce each network to central nodes and

connecting bridges. Compounds are binodal with a 6,6-

able breathing eﬀect. The parent material, compound 1, was

obtained under mild and simple microwave irradiation

conditions (100 °C during 1 h). Upon ﬁltration it undergoes

a spontaneous single-crystal to single-crystal (SC−SC) trans-

formation, leading to the formation of a new phase-pure

material, 2. Structural studies showed that this transformation

was promoted solely by the removal of the solvent, which

prompted us to perform more detailed dehydration studies on

1

3 2

connected network and a total Schaﬂ

̈

i symbol of {4 .6 }-

4 .6 .8} (Figure S2). In fact, the three compounds have similar

asymmetric units composed of one metal center and one

8

6

{

2. As a result, compound 3 was isolated as a pure phase when 2

3

−

was dehydrated overnight at 110 °C. Additionally, we

concluded that the dehydration process could not be

completely reverted in the presence of water, but only when

using methanol: compound 3 in methanol is converted into 4,

which shares the same crystal structure with 2 (see section 3.6

for further details). This selectivity toward methanol happens

because the channels of the MOFs are essentially formed by the

hydrophobic part of the ligand (benzene rings), thus the higher

aﬃnity toward an organic solvent, rather than just water,

ultimately promoting a fast reversible eﬀect.

H btp residue (four independent phosphonate groups).

5

3

+

Taking advantage of the presence of diamagnetic Y metallic

centers, we have conﬁrmed the number of crystallographic

independent phosphonic acid groups through the use of solid-

3

1

state NMR studies (for the air-stable compounds). The

P

MAS spectrum of 2 shows, in the isotropic region, two well-

resolved sharp peaks and a third broad peak, corresponding to

two resonances, centered at ca. 1.6, 6.8, 11.1, and 12.4 ppm

respectively (Figure S7 ). Peak deconvolution and ﬁtting

conﬁrm that there are four independent phosphorus sites,

which correspond to a total of one organic ligand in the

asymmetric unit. The same analysis was performed for 3: the

In order to conﬁrm the phase purity of bulk [Y(H btp)]·

5

2

.5H O (2) and (H O)[Y (H btp)(H btp)]·H O (3) materi-

2 3 2 5 4 2

31

als, powder X-ray di ﬀ raction studies were performed at ambient

temperature (Figure S3 ). Elemental analysis, electron micros-

copy (Figures S4 to S6 ), solid-state NMR (Figure 1 and Figures

S7 and S8 ), and FT-IR spectroscopy (Figure S13) were used in

P MAS spectrum shows, in the isotropic region, resonances

centered at ca. 2.6, 9.9, 11.2, and 11.8 ppm (Figure S8). One of

the peaks appears as a broad signal due to the overlapping of

three resonances, as established after peak deconvolution. In

E

DOI: 10.1021/acs.inorgchem.6b02199

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

Figure 2. (top) Distorted octahedral coordination environments of Y³⁺present in the crystal structures of compounds 1 to 3. (bottom) Channel

voids present in frameworks 1 to 3 calculated using Mercury Software (1.2 Å of probe radius and 0.7 Å as grid spacing using the accessible solvent

39

volume algorithm).

4

0

short, the bulk crystalline materials have four independent

phosphorus sites in good agreement with the performed

crystallographic studies.

to employ the adaptation of the method proposed by Baur to

calculate the distortion index (DI) for bonds and angles:

n

i=1

∑

|d(Y − O) − d(Y − O)_a_v_e_r_a_g_e|

i

In 3 one of the hydrogen atoms is disordered, leading to the

formation of a hydronium ion. This arises from the fact that the

hydrogen in O12 “jumps” from this atom to the symmetrically

adjacent oxygen, which leads to a negative charge of the

network. This negative charge is then balanced by the presence

of this hydronium cation. The presence of the hydronium ion

^D^Ibond

^D^Iangle

=

n

∑

|d(Y − O)

|

i=1

i

(1)

n

i=1

∑

|∠(O − Y − O) − ∠(O − Y − O)ideal^|

i

n

i=1

∑

|∠(O − Y − O)_i|

(

2)

1

was unequivocally conﬁrmed by solid-state H NMR studies

2

1

where O corresponds to any coordination site, and the

subscripts i and average/ideal indicate individual and average/

ideal bond lengths and angles. For an octahedron, the values

related to the angles should be calculated separately for the cis

and trans angles, which are compared to their ideal values (90

and 180°, respectively). The distortion indexes (DI) calculated

for the three compounds are given in Table 2. As one can infer,

(Figure 1).

The metal centers have the same coordination geometry in

all compounds, being hexacoordinated to six distinct

phosphonate moieties arising from six symmetry-related

organic linker residues: {YO }. The coordination geometry

6

resembles slightly distorted octahedra (Figure 2, top).

Comparing materials 1, 2, and 3 we observe a drastic reduction

3

in the overall unit cell volume (from 2710 Å to 2092 Å to 961

Table 2. Distortion Index (DI) for Bonds and Angles (cis

and trans) of the Coordination Spheres of Compounds

3

Å ) and also symmetry change (from monoclinic to triclinic),

corresponding mainly to a reduction of the overall solvent-

accessible volume (Figure 2, bottom). This reduction is a direct

consequence of the transition from a more “open” structure to

a more compact and closed form.

[

(

Y(H btp)]·5.5H O (1), [Y(H btp)]·2.5H O (2), and

5 2 5 2

H O)[Y (H btp)(H btp)]·H O (3)

3

2

5

4

2

^D^Iangle

The bond lengths and angles of the coordination polyhedra

are comparable to those reported by our research group for

DI_b_o_n_d

cis

trans

1

2

3

0.010

0.008

0.009

0.045

0.050

0.036

0.041

0.058

0.039

3+

other Ln -based phosphonate compounds. The reﬁned Y−O

distance ranges are 2.190(12)−2.260(5) Å (Δ = 0.07 Å) for 1;

2

.200(3)−2.270(3) Å (Δ = 0.5 Å) for 2; 2.1899(16)−

3+

.2845(15) Å (Δ = 0.095 Å) for 3. The reﬁned Y octahedra

the DI_b_o_n_ddoes not change signiﬁcantly for each material.

However, the SC−SC transformation from 1 to 2 leads to a

higher angle distortion, in particular for the trans angles. The

loss of three water molecules per asymmetric unit has an eﬀect

on the pore size, leading not only to a higher distortion in the

coordination sphere of the metal center but also to a change in

the organic linker. As depicted in Figure 3 there is an evident

slight rotation between the aromatic rings from 7.1° to 12.5°.

On the other hand, the SC−SC transformation from 2 to 3 has

the contrary eﬀect. With the removal of 1.5 water molecules per

asymmetric unit the organic linkers exhibit an identical mutual

internal rotation between the aromatic rings as observed in 1

(7.1° for 1 and 7.9° for 3) (Figure 3).

are all slightly distorted from the perfect geometrical solid, with

these distortions changing with the framework transformation.

The O−Y−O angles are slightly diﬀerent from the ideal values

(

90° and 180° for the cis and trans angles, respectively). The cis

and trans octahedral angles were found to be, respectively,

between 81.6(4) and 95.82(16)° (Δ = 14.22°) and 169.7(4)

and 175.94(16)° (Δ = 6.26°) for 1, between 81.43(12) and

1

=

1

01.58(11)° (Δ = 20.15°) and 164.39(12) and 175.31(12)° (Δ

10.92°) for 2, and between 84.49(5) and 98.70(6)° (Δ =

4.21°) and 171.14(6) and 174.27(5)° (Δ = 3.13°) for 3.

These results can already provide some insight of the overall

degree of distortion in the octahedra. However, in some cases,

discrete values can be misleading. To overcome this we decided

F

DOI: 10.1021/acs.inorgchem.6b02199

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

Figure 3. (top) Schematic representation of the coordination environment and organic linker backbone of compounds 1−3 and (bottom) overlay

3

9

between structures 1−3. The overlay was performed using the Mercury Software.

The crystallization water molecules interact with the

networks by way of supramolecular contacts (hydrogen

interactions) in all compounds. In 1 only hydrogen bonds

established between water molecules and the −POH groups of

the main structure are present, with a solvent accessible volume

calculated of 12.3% per unit cell (calculated using Mercury

Software). The high solvent disorder and weak interactions

between crystallization water molecules and the −POH groups

facilitate the transformation, which, upon ﬁltration, leads to the

formation of 2. The release of some water molecules is

accompanied by a reduction of the pore size and a distance

decrease between metal centers of opposite sides (Figure 4).

While in 1 the metal centers are separated by 13.6328(18) and

13.0848(18) Å, in 2 they are closer, separated by 10.5525(10)

and 8.9763(9) Å respectively, with a pore size calculated of

1.2% per unit cell. This transformation leads to the formation of

a more stable compound, mainly by stronger interactions

between water molecules and −POH groups. Not only that, but

2 forms hydrogen bonds between −POH groups of opposite

sides of the channel, leading to a more compact and robust

structure (Figure 5). With an increase of temperature (by

applying a thermal treatment at 110 °C or higher) some

hydrogen bonds are broken and a new SC−SC transformation

is observed. This follows the same mechanism as for 2, in which

some of the remaining water molecules are removed from the

channels of the framework. With only one water molecule per

3

9

G

DOI: 10.1021/acs.inorgchem.6b02199

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

Figure 4. (left) Schematic representation of the crystal packing of compounds 1-3 viewed in perspective along the [100] direction of the unit cell

the 6,6-connected binodal topology is overlapped in all representations). (right) Cross-section of the channels viewed along the a axis. The dashed

blue lines represent the hydrogen interactions between the water molecules and the POH groups.

(

asymmetric unit, 3 is maintained mainly by hydrogen bonds

between −POH groups of opposite sides of the channels. As

for the previous transformation, there is a visible decrease in

solvent accessible volume (reduction to 0.2% per unit cell).

However, the metal centers of opposite sides of the channels

seem to be slightly farther apart (10.5525(10) and 8.9763(9) Å

for 2 and 10.7455(9) and 9.0513(7) Å for 3) (Figure 5). This is

due to the spatial distribution of the organic linkers. While in 1

and 2 the ligands form lozenge-based tunnels when connected

to the metal centers, in 3 they exhibit a more rectangular shape.

This distribution may also explain the lower angle distortion for

observed 2.7% weight loss is equivalent to one water molecule).

In order to evidence this reorganization, compound 2 was

calcined at 350 °C. The resulting residue was analyzed by FT-

IR in order to identify the typical ν(P−O−P) stretching

−

1

vibration, which normally appears in the 930−915 cm

42

range. Results were inconclusive due to the overlapping of

vibrational modes in this spectral region. Nevertheless,

considering the amount of phosphonic acid groups, as well as

their proximity in the framework, the possibility of their

rearrangement toward the formation of pyrophosphonate

groups seems to be a plausible possibility.

3

as discussed previously.

.4. Thermogravimetry and Thermodiﬀractometry.

The thermal stability of compound [Y(H btp)]·2.5H O (2)

Variable-temperature powder X-ray diﬀraction studies on

3

[Y(H btp)]·2.5H O (2) corroborate the aforementioned

5

2

assumptions concerning the release of the water molecules

and the concomitant phase modiﬁcations (Figure S10): from

ambient temperature to ca. 350 °C, the structure of 2 changes,

leading to the formation of new crystalline phases. The

structure of material 2 starts to collapse from ca. 550−600 °C,

becoming almost amorphous at 800 °C. At ca. 1200 °C,

powder X-ray diﬀraction studies (PDF4+ 2014 release ICDD

database) show the formation of a residue composed of yttrium

5

2

was investigated between ambient temperature and ca. 800 °C

Figure S9), providing additional information on the hydration

(

level of the bulk compound. The crystallinity of the bulk

material was further evaluated by employing in situ variable

temperature powder X-ray diﬀraction studies (VTPXRD;

Figure S10), in the 25−1200 °C temperature range.

Between ambient temperature and ca. 250 °C, compound 2

loses approximately 7.5% of mass in two consecutive steps,

corresponding to the release of ca. 2.5 water molecules of

crystallization. This value agrees well with the calculated one

phosphate (YPO , ICDD 00-042-0501).

4

An identical set of studies were performed for (H O)-

3

[Y (H btp)(H btp)]·H O (3) (Figures S11 and S12). The ﬁrst

2

5

4

2

(

ca. 7.4%). A third weight loss, corresponding to 2.7%, occurs

weight loss occurs between ambient temperature and ca. 190

°C, corresponding to the release of two water molecules of

crystallization. The experimental value of ca. 3.2% agrees well

with the calculated one (ca. 3.1%). Between ca. 190 and 350 °C

is observed a second weight loss (ca. 3.4%), also attributed to

the release of two water molecules originating from the

between ca. 250 and 350 °C. According to our previous

4

1

studies the phosphonate groups of the organic ligand in the

framework may suﬀer a rearrangement at this temperature

range, leading to the formation of pyrophosphonates with the

consequent release of water molecules (in this case the

H

DOI: 10.1021/acs.inorgchem.6b02199

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

provide important information concerning the diﬀerent

chemical environments of these moieties in the compounds.

Compound 2 possesses in its pore structure only solvent

water molecules. This structural feature is markedly visible in

the FT-IR spectra of the compounds, particularly in the 3600−

650 cm⁻spectral range that is highly dominated by the O−H

1

2

vibrational mode of water molecules. While for 2 a broad band

includes several vibrations, for 3 more deﬁned vibrational

modes are observed in this particular range. A well-deﬁned

vibration band centered at 3505 cm⁻is attributed to the

hydronium cation and conﬁrms a strong hydrogen bond

veriﬁed previously in the performed single-crystal X-ray studies

1

4

3

−1

of 3. The broad band located at 3375 cm is attributed to

crystallization water molecules. ν(POH) and ν(C−H)

stretching vibrational modes of medium intensity are also

−1

observed at 3250 and 3075 cm , respectively.

Below 1860 cm⁻the FT-IR spectrum of all materials is very

complex, with a large number of medium-to-very strong

vibration bands, mainly arising from the organic ligand itself.

1

42

Based on the literature, the medium intensity bands between

1

860 and 1560 cm⁻are attributed to the ν(CC) vibration in

functionalized benzene rings, as well as the in-plane

deformation of water molecules. The peaks at ca. 1400 cm⁻

with medium and weak intensity, respectively, are attributed to

the P−C bond’s deformation. The ν(PO), ν(P−O), and

1

−1

ν(P−C) vibration modes appear between 1280 and 600 cm

(

with strong to very strong intensity).

.6. Heterogeneous Catalysis. The catalytic performance

of [Y(H btp)]·2.5H O (2) was investigated in the ring-opening

3

5

2

reaction of styrene oxide with methanol at 35 °C. The initial

catalytic activity of the MOF was 138 mmol g_M_O_F⁻

1

h

−1

based

on conversion at 15 min; 2-methoxy-2-phenylethanol was the

sole product formed with 96% yield after 2 h of reaction

−1

(

catalyst load of 3.3 g L ). The excellent product selectivity

reached with these MOFs is a great advantage for applications

in the pharmaceutical sector where compounds possessing 1,2-

44−48

alkoxy alcohol groups are important intermediates,

the synthesis of tricyclic beta-lactam antibiotics.

e.g., for

49

For comparative purposes, the ligand and metal precursors of

Figure 5. Schematic representation of the crystal packing of (a)

the MOF, namely, H btp and YCl ·6H O, were tested as

[

(

Y(H btp)]·5.5H O (1), (b) [Y(H btp)]·2.5H O (2), and (c)

8

3

2

5

2

5

2

catalysts under similar styrene oxide reaction conditions (H btp

H O)[Y (H btp)(H btp)]·H O (3) viewed in perspective along the

8

3

2

5

4

2

[

100] direction of the unit cell. Supramolecular interactions involving

and YCl were used in amounts equivalent to the moles of

3

the water molecules and phosphonate groups are emphasized.

ligand or metal found in the MOF catalytic tests). Both

precursors promoted the conversion of styrene oxide to 2-

methoxy-2-phenylethanol with 100% selectivity (Figure S14).

rearrangement of the phosphonic acid groups in order to, most

likely, form pyrophosphonate moieties. After a plateau of

approximately 200 °C (between 350 and 550 °C) in which the

dehydrated material remains stable, the material decomposes.

Thermodiﬀractometry studies show that the structure of 3

remains unaltered up to ca. 120 °C. After this temperature, and

up to ca. 200 °C, a new crystalline phase is formed (the

dehydrated form of 3). The possible formation of pyrophosph-

onates led to a new rearrangement of the framework of 3

The Bro

Lewis acidity of YCl

the alcoholysis of the epoxide. For YCl

conversion reached a plateau after 2 h of reaction, suggesting

the deactivation of this precursor (it was completely soluble,

acting as a homogeneous catalyst). In contrast, H btp was far

more active (100% conversion to 2-methoxy-2-phenylethanol

within 15 min of reaction) than YCl ·6H O (9%/22% of

conversion at 15 min/2 h), suggesting that Bronsted acidity is

̈

more favorable for this reaction. Accordingly, the high 2-

methoxy-2-phenylethanol yields reached for 2 may be

essentially due to Bronsted acid sites.

̈

The lower catalytic activity of 2 in comparison to H btp may

̈

nsted acidity of H

·6H O seem to play an important role in

·6H O, styrene oxide

8

btp and, on the other hand, the

3

2

3

2

8

3

2

(

between 200 and 400 °C). An amorphous residue appears at

ca. 750 °C.

3.5. FT-IR Spectroscopy. FT-IR spectroscopy studies

clearly support the structural features unveiled by the X-ray

diﬀraction studies. Figure S13 depicts selected regions in the

spectra of phase-pure compounds 2 and 3. Relevant diﬀerences

in some spectral regions are noticeable despite the overall

identical proﬁles. The most striking diﬀerences are assigned to

vibrational modes of crystallization water molecules, which

8

be partly due to diﬀerences in the amount of eﬀective active

acid sites, because the free organic ligand possesses four

phosphonic acid groups per molecule, whereas when it is

coordinated in the MOF structure the ligand possesses a

smaller number of free OH groups (a fraction of the OH

I

DOI: 10.1021/acs.inorgchem.6b02199

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

groups are deprotonated and coordinated to the metal centers).

reaction rate, and the (dimethoxymethyl)benzene yields at 30

min increased from 49% to 89%, respectively (Figure S16).

These results are outstanding in comparison to those for the

1D MOF [La (H nmp) (H O) ]·4.5H O tested under identi-

On the other hand, H btp was completely soluble in the

8

reaction medium, and, therefore, it acted as a homogeneous

acid catalyst, whereas the MOF was completely insoluble and

acted as a true heterogeneous catalyst. The heterogeneous

nature of the catalytic reaction of styrene oxide over the MOF

was, indeed, assessed by leaching tests (details given in the

Experimental Section). After separating the solid catalyst from

the reaction mixtures by membrane ﬁltration at the reaction

temperature, the conversion of styrene oxide ceased for the

remaining reaction time, indicating the absence of soluble active

species desorbed from the MOF (Figure S15). An important

advantage of MOF materials over homogeneous catalysts is that

the former are easily separated from the reaction mixtures,

which can be eﬃciently carried out by ﬁltration or

centrifugation.

2

3

2

4

2

cal benzaldehyde reaction conditions, which led to 94%

(dimethoxymethyl)benzene yield only after 20 h (catalyst

−1

50

loading of 20 g_M_O_FL ) (Table S4). The superior catalytic

performance of 2 compared to various MOFs investigated for

5

0,52,79,81−85

this reaction is clearly demonstrated in Table S4 .

In

order to gain mechanistic insights into the acetalization

reaction, precursors H btp and YCl ·6H O were also tested

8

3

2

for the benzaldehyde conversion (the precursors were used in

amounts equivalent to the moles of MOF added in catalytic

−1

tests using 3.3 g_M_O_FL ). H btp and YCl ·6H O led to

8

3

2

extremely fast conversion of benzaldehyde to

dimethoxymethyl)benzene, which was formed with 91% and

6% yield at 15 min of reaction, respectively (Figure S16).

Hence, Bronsted and Lewis acidity can be highly favorable for

(

9

To the best of our knowledge there is only one lanthanide-

containing MOF, the 1D [La (H nmp) (H O) ]·4.5H O,

2

3

2

4

2

̈

reported by our group, which led to comparable catalytic

the acetalization reaction. Comparably high product yields were

50

results (Table S3 ). Various transition metal containing MOFs

have been previously tested as catalysts for the methanolysis of

reached after 2 h reaction in the presence of 2, which may be

due to Lewis (e.g., defect Y-sites) and/or Bro

phosphonic acid groups). On the other hand, it is possible that

Lewis acid Y-sites induce Bronsted acidity by polarizing water

molecules which are formed as coproduct of the acetalization

reaction. The Bronsted acid catalyzed reaction of benzaldehyde

̈

nsted acid sites

41,51−63

styrene oxide (results compared in Table S3 ).

Although

(

it is diﬃcult to make clear and fair comparisons due to the

diﬀerent reaction conditions employed between diﬀerent

studies, the catalytic performance of 2 seems to compare

̈

5

2

̈

favorably to various other MOFs. For example, [Fe(BTC)]

60

may take place via protonation of the carbonyl group and

reaction with methanol to give a hemiacetal intermediate, which

further reacts with another methanol molecule to give the acetal

and MIL-101(HPW) led to 99% styrene oxide conversion in

less reaction time than 2, but the reaction temperature and

catalyst loadings were higher, and a lower initial concentration

of styrene oxide was used in the case of MIL-101(HPW), which

are favorable factors for a faster kinetics. Good catalytic

results were reported by Zhou et al. but for a MOF with

82

product, (dimethoxymethyl)benzene (Scheme S1 ). While,

the Lewis acid catalyzed mechanism may be similar to that

60

82

62

proposed by Janiak et al., involving coordination of the

alcohol and aldehyde reactants to Lewis acid sites leading to

chelating intermediates, which are converted to the acetal and

water (Scheme S2 ).

diﬀerent organic moieties (MIL-101(SO H)) which led to 99%

3

conversion at 10 min of reaction, using relatively low initial

concentration of styrene oxide.

The recyclability of the MOF was investigated by carrying

Compound 2 was further explored in the acid-catalyzed

acetalization of benzaldehyde at 35 °C. Results for this reaction

were more thoroughly explored in this work mainly because

acetalization reactions are broadly used and very important in

organic synthesis. They allow the protection of carbonyl groups

of highly functionalized (reactive) molecules, improving the

chemical stability toward various reagents such as bases and

out four consecutive batch runs of benzaldehyde conversion

−1

(

²⁰^gMOF L , at 35 °C; Figure 6). Diﬀerences in the initial

6

4

oxidants. In particular, acetals of benzaldehyde are used in

diﬀerent sectors of the chemical industry, such as the

6

5

production of perfumes and ﬂavors, pharmaceuticals,

6

65,67,68

plasticizers, cosmetics, food additives, beverages,

65,67,69

solvents, and other useful chemicals.

Several types of

solid acid catalysts have been explored for the acetalization of

7

0

benzaldehyde, such as zeolites, transition metal mixed

7

1

2−

72

73,74

oxides, Fe-doped SO /SnO₂, carbon based catalysts,

4

7

5,76

77

ion-exchange resins,

SO H-MIL-101. The reaction of benzaldehyde with methanol

and MOFs such as MIL-100Fe and

7

8

3

in the presence of 2 at 35 °C was fast, resulting in

(

dimethoxymethyl)benzene as the only product formed with

96% yield in 2h (Figure S16 ). The catalytic performance of 2

for the acetalization reaction was similar, when compared to the

alcoholysis reaction. The acetalization of benzaldehyde involves

formation of water as coproduct, which can negatively aﬀect the

product yield by shifting the equilibrium to the formation of

Figure 6. Reaction of benzaldehyde with methanol to aﬀord

dimethoxymethyl)benzene in the presence of the heterogeneous

catalyst [Y(H btp)]·2.5H O (2) in four consecutive batch runs.

Reaction conditions: 35 °C, 4 h, catalyst load = 20 g_M_O_FL .

(Dimethoxymethyl)benzene was formed with 100% selectivity.

5

0,79,80

benzaldehyde.

Nevertheless, very high conversions were

(

reached for 2, which may be partly due to favorable surface

polarity and competitive adsorption eﬀects. Increasing the

5

2

−1

catalyst loading from 3.3 g_M_O_F

L

to 20 g_M_O_F

L

enhanced the

J

DOI: 10.1021/acs.inorgchem.6b02199

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

catalytic activity were observed between runs, which may be

partly due to some fragmentation of the particles of the catalyst.

Nevertheless, for the investigated material very high benzalde-

hyde conversions were reached for four consecutive batch runs

have been carried out for the composition with the least water

content (H O)[Y (H btp)(H btp)]·H O (3) MOF, with the

3

2

5

4

2

expectation that the material can eﬀectively absorb further

water molecules leading to enhanced proton transport, possibly

associated with a phase transition to the more hydrated phases,

[Y(H btp)]·2.5H O (2) or even [Y(H btp)]·5.5H O (1).

(93−98% at 1 h reaction), with (dimethoxymethyl)benzene

being always the sole reaction product (100% selectivity).

Material 2 retained its structural integrity during subsequent

runs, which was con ﬁ rmed by PXRD (Figure S17) and FT-IR

spectroscopy (Figure S18) of the used solids.

5

2

5

2

Measurements were conducted on two (H O)[Y (H btp)-

3

2

5

(H btp)]·H O (3) samples, one corresponding to the as-

4

2

prepared material, hereafter referred to as “as-prepared”, and

another that was previously dried at 120 °C overnight, which is

identiﬁed as “predried”. The powder could be easily pressed

into disk-shaped pellets, free from major defects and retaining

its crystallinity, as well as structural integrity. In agreement with

our expectations, the impedance spectra for both samples

display a tremendous inﬂuence regarding relative humidity. At

RH of 80% and lower, the spectra are dominated by one single

semicircle and one capacitive tail at low frequency, correspond-

ing to the bulk resistance of the pellet and the electrode

relaxation, respectively (Figures S22 and S23). Increasing RH

reduces the amplitude of the semicircle, which is indicative of

the lowering of the ohmic resistance of the sample (R). We

additionally observe an increase of the frequency at the top of

the semicircle (f_p_e_a_k), which is a measure of the relaxation

frequency of the ionic polarization. Assuming that a simple

description of the ionic relaxation by the usual parallel RC

The same studies for the alcoholysis of styrene oxide and

acetalization of benzaldehyde were performed using (H O)-

3

[

Y (H btp)(H btp)]·H O (3). It was observed that during the

2 5 4 2

ﬁrst batch run of the catalytic studies compound 3 was

converted into [Y(H btp)]·H O·0.5(MeOH) (4). This com-

5

2

pound shares the same crystalline phase with 2 as ascertained

by PXRD (Figure S19 ) and FT-IR spectroscopy (Figure S20).

Methanol uptake by compound 3, and a subsequent phase

transition to 4, was further corroborated by thermogravimetry

(Figure S21). Compound 4 loses 2.6% (calculated ca. 2.7%) of

its weight between ambient temperature and ca. 70 °C,

corresponding to the release of 0.5 molecule of methanol. As

expected, after the release of the methanol molecules, the

thermal behavior of compound 4 is very much identical to that

of 3 (Figure S11).

3.7. Protonic Conductivity. Proton conducting materials

have gained a lot of interest in recent years due to their many

applications, especially for hydrogen fuel cells. Metal−organic

frameworks are some of those materials. Structure-deﬁned

MOFs possess several supramolecular interactions with guest

solvents, and so they have been studied due to the high

protonic conductivity they exhibit. Yet the relationship between

the hydrogen-bonding pathways and proton conductivity is not

always suﬃciently investigated. The exact network of the

conﬁned guests in the pores is often not determined because of

structural disorder, even when the framework structure is clear.

In this work, the possibility to determine the MOF

architectures for the breathing system using single-crystal X-

ray diﬀraction proved to be an advantage because of the

opportunity to visualize the potential ion transfer pathways

within the network. The 1D channels with surface non-

coordinated −POH groups of the MOFs herein studied have

an obvious potential to enable high levels of protonic

conductivity by accommodating a variable amount of water

molecules. To clarify this relationship between conductivity and

structure pathways we tried to illustrate the hydrogen-bonding

networks between acidic species and guest water molecules in

materials 1, 2, and 3 (Figure 4). We were interested in the

analysis of viable proton conduction pathways throughout the

structure of the synthesized materials and veriﬁed that the

hydrogen bonding networks of acidic species and guest

molecules was extremely well-ordered for material 3, although

the water molecules embedded in the narrow pores were

separated by a considerable distance. This problem, however,

was not occurring in the remaining materials (1 and 2): even

though not all hydrogen bonds could be distinguished due to

the high disorder, the guest molecules are much more dispersed

throughout the channels, contributing to a much more intricate

arrangement of hydrogen bonds that could facilitate the proton

equivalent circuit with the peak frequency is given by f

=

peak

−1

(

2πRC) , one concludes that the capacitance C remains

constant, or even increases, in agreement with a slight increase

of the dielectric constant expected for a material with higher

water content. Under saturated conditions (98% RH), the

magnitude of decrease of R is such that f_p_e_a_kincreases beyond

the measuring range of the LCR meter (2 MHz) and only the

electrode impedance is observed. In this case, R is given by Z′

at the high frequency intercept with the real axis of the Nyquist

plot.

Figure 7 shows the conductivity data for both the “as-

prepared” and “predried” samples in Arrhenius plots coordi-

18

conducting mechanism. In addition, 3 arose as a very

Figure 7. Arrhenius plots of the protonic conductivity of (H O)-

3

promising material due to the natural proton transfer occurring

[

Y (H btp)(H btp)]·H O (3) samples (predried pellet, open symbols;

2 5 4 2

+

during the desolvation process, leading to the presence of H O

3

as-prepared pellet, solid symbols). The lines for RH 80% and lower

humidity are ﬁts to the Arrhenius equation, and a simple guide for the

eye for 98% RH.

species in the material. Taking all this into account,

conductivity studies under variable relative humidity (RH)

K

DOI: 10.1021/acs.inorgchem.6b02199

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

nated for variable RH conditions. The ﬁgure conﬁrms that the

large increase in conductivity with increasing humidity

registered for 3 is most likely a result of the induced absorption

of water by the material. At and below 80% RH, the

temperature dependence of the conductivity displays the

typical linear Arrhenius trend, with activation energy in the

range 0.26−0.48 eV, with somewhat lower values for the

predried sample, and especially the as-prepared sample at 20%

RH (0.26 eV) (Table 3). The latter may be explained by kinetic

ductivity is attributed to a thermal activation mechanism which

led to a small structural and/or textural change.

Compound 3 shows similar conductivity values at low

temperatures (40 and 60 °C) when compared with several

90

MOFs. On the other hand, it also shows an excellent

−

2

−1

conductivity at 98% RH (2.58 × 10 S cm ), being one of the

best results reported for these kinds of materials. It is

comparable to PCMOF21/2, with 2.1 × 10 S cm at 85

91

−2

−1

° C a n d 9 0 % R H , a n d o₂n l y s u r p a s s e d b y

9

−2

−1

{

[(Me NH ) (SO )] [Zn (ox) ]} , (4.2 × 10 S cm ,

2 2 3 4 2 2 3 n

93

Table 3. Activation Energy in eV for the Protonic

Conductivity Measured under Variable Relative Humidity

ambient temperature and 98% RH) and H SO @MIL-101

2 4

(6.0 × 10⁻S cm at 80 °C and 20% RH), the latter actually

being a mixture of sulfuric acid and a MOF. When we compare,

however, the synthesis and properties of all materials, both 3

and 2 arise as the more stable compounds which can be

obtained using simple methodologies, with no need for

demanding storage conditions (when compared to

2

−1

activation energy (eV)

a

2

0

40

60

80

predried pellet

0.35

0.26

0.37

0.40

0.44

0.48

0.40

0.46

as-prepared pellet

91

a

PCMOF21/2), using faster and more sustainable reaction

conditions (compared to {[(Me NH ) (SO )] [Zn (ox) ]} )

n

RH (%).

92

2

2 3

4

2

3

and with no need of several synthetic steps or high temperature

conditions (which was the case of MIL-101 and the subsequent

reasons dictated by the larger water content in this sample,

which responds diﬀerently when exposed to the initial dry 20%

RH environment (the measurements were carried out with

increasing temperature, at each RH). Nevertheless, the range of

activation energies is in line with those reported for other

MOFs and suggests the structural diﬀusion of protons (along

the water domains formed in the vicinity of the acidic

phosphonate groups) as the dominating charge transport

mechanism in these materials. Unfortunately, the amount of

absorbed water should be rather low in this humidity range

93

H SO @MIL-101).

2

4

. CONCLUSIONS

A new family of materials exhibiting unique multifunctionality

was prepared using a methodology based on microwave-

assisted synthesis (MWAS). The three novel open-framework

phase-pure MOFs [Y(H btp)]·5.5H O (1), [Y(H btp)]·

8

6

5

2

5

2.5H O (2), and (H O)[Y (H btp)(H btp)]·H O (3) were

2

3

2

5

4

2

obtained in bulk quantities. 1 is isolated using a simple, fast, and

high yield synthetic process, when compared to more

conventional methodologies, while 2 and 3 are obtained by

single-crystal to single-crystal (SC−SC) transformations: 2 is

formed after ﬁltration of 1, and 3 is prepared by heating 2 at

110 °C overnight. The structural relationships between the

three networks and their breathing eﬀect were thoroughly

studied. It was veriﬁed that, after the removal of lattice water

molecules at moderate temperatures, the crystalline three-

dimensional framework is maintained. Single-crystal X-ray

diﬀraction showed that the three structures are virtually the

(

≤80% RH) and, as a result, the magnitude of the conductivity

−5 −1

is rather low, only marginally exceeding 10 S cm at 94 °C

and 80% RH.

At 98% RH, Figure 7 demonstrates, however, a spectacular

−5

enhancement of the conductivity from 7.70 × 10 to 1.94 ×

−

2

−1

1

0

S cm between 60 and 80 °C, which further increases to

1

−

.03 S cm at 94 °C. In these conditions the hydrogen bonds

maintaining the structure are weakened and a higher quantity of

water ﬂows through the pores of 3, which eventually transforms

into the more hydrated [Y(H btp)]·2.5H O (2) phase. This

5

2

was conﬁrmed by the PXRD pattern collected from the pellet

after impedance measurements at 98% RH/94 °C, which shows

clear evidence of formation of 2 (Figure S24, blue pattern).

This X-ray powder pattern collected at ambient temperature

contains reﬂections of both compounds 3 and 2, probably due

to the reversibility of the 3 → 2 phase transition below 80 °C. It

should be noticed that the same partial phase transformation is

observed by rehydrating freshly synthesized material 3 under

more drastic hydrothermal conditions (Figure S24, green

pattern). The additional water molecules present in 2, as well as

the higher mobility due to the increase in pore size, allow the

̈

same, a binodal 6,6-connected network with a total Schaﬂi

13

2

8 6

symbol of {4 .6 }{4 .6 .8}, with the sole diﬀerence being the

number of crystallization water molecules. The present study

further indicates that the yttrium coordination environment is

composed exclusively of phosphonate oxygens, i.e., there are no

water molecules coordinated to the metal centers. This

structural feature clearly contributes to the observed mechanical

robustness and thermal stability of the materials, particularly

evident for material 3, which shows an outstanding thermal

stability up to ca. 600 °C. A detailed and exhaustive literature

20,75,94−102

search

reveals that 3 is indeed one of the most stable

87

transport of a higher amount of protons. This abrupt increase

reported MOFs based on a tetraphosphonic organic linker

concerning exposure to humidity and mechanical and thermal

robustness.

88

has been reported in the past. Tominaka and collaborators

−9

have reported a rapid raise in conductivity from 5.0 × 10 to

5

−1

3

6

.9 × 10⁻S cm due to the increase of RH from 50% RH to

After full characterization in the solid state, properties

envisaging possible applications of the materials were

investigated: usage in heterogeneous catalysis and protonic

conductivity (for 2 and 3, respectively). Outstanding perform-

ance results were observed for both applications. 2 showed

excellent catalytic activity in two distinct acid-catalyzed

reactions: ring-opening reaction of styrene oxide with methanol

at 35 °C, with the formation of 2-methoxy-2-phenylethanol as

the sole product with 96% yield at 2 h of reaction; in the

7% for ((CH ) NH )[Li Zr(C O ) ] at 17 °C. Bazaga-

Garcıa and co-workers have reported a similar abrupt increase

at 98% RH visible with the increase of the temperature: Ca-

PiPhtA-I (Ca [(HO PC H COOH) ] [(HO PC H -

3

2

4 4

8

9

́

2

3

6

3

2

3

6

3

(

COO) H)(H O) ]·5H O) shows an increase in conductivity

2

−

4

−3

−1

from 5.7 × 10 to 1.3 × 10 S cm between 24 and 40 °C.

The water content remains unaltered before and after the

change in temperature; consequently the increase of con-

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DOI: 10.1021/acs.inorgchem.6b02199

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

acetalization of benzaldehyde with 94% conversion into

through the FCT/MEC and when appropriate coﬁnanced by

FEDER under the PT2020 Partnership Agreement. We also

thank FCT for funding the R&D project FCOMP-01-0124-

FEDER-041282 (ref. FCT EXPL/CTM-NAN/0013/2013).

FCT is also gratefully acknowledged for the Ph.D. grants

SFRH/BD/84495/2012 and SFRH/BD/84231/2012 (to

A.D.G.F. and R.F.M., respectively), the postdoctoral research

grants SFRH/BPD/89068/2012, SFRH/BPD/94381/2013,

and SFRH/BPD/96665/2013 (to M.M.A., to S.M.F.V., and

to P.C.B., respectively), and the Development Grant IF/01174/

2013 (to F.M.L.F.).

(

dimethoxymethyl)benzene at 1 h of reaction. The superior

catalytic performance of 2 compared to various MOFs

investigated for this reaction is clearly demonstrated in Table

S4 . For the ring-opening reaction, the present material

compares very well with one of our previously reported

materials, [La (H nmp) (H O) ]·4.5H O, with both being

among the best described to date.

50

2

3

2

4

2

Concerning the protonic conductivity properties of 3, a

tremendous inﬂuence regarding relative humidity was veriﬁed.

Although the conductivity marginally exceeds the 10⁻S cm

5

−1

up to 94 °C and 80% RH, when exposed to 98% RH, a great

increase is observed. At this value for the humidity an increase

REFERENCES

■

−5

of conductivity between 60 and 80 °C (from 7.70 × 10 to

(

1) Ferey, G.; Serre, C. Large breathing effects in three-dimensional

−

2

−1

1

0

.94 × 10₋S cm ) was registered, which further increases to

porous hybrid matter: facts, analyses, rules and consequences. Chem.

Soc. Rev. 2009, 38, 1380−1399.

(2) Ferey, G. Swelling Hybrid Solids. Z. Anorg. Allg. Chem. 2012, 638,

.03 S cm ¹at 94 °C. 3 is, therefore, one of the best performing

MOFs reported to date concerning proton conductivity, with

conductivities in the same magnitude of only two other

reported materials in the literature. We note, however, that an

important advantage of 3 in comparison to these other

materials resides with its inherent stability at ambient

conditions (temperature and humidity), as well as its

sustainable, simple and easy to perform synthesis methodology.

A further study on material 3 to conﬁrm the ﬂexibility of the

framework showed the high aﬃnity of the material toward

methanol, leading to the formation of [Y(H btp)]·H O·

1

(

897−1909.

3) Triguero, C.; Coudert, F. X.; Boutin, A.; Fuchs, A. H.; Neimark,

A. V. Understanding adsorption-induced structural transitions in

metal-organic frameworks: From the unit cell to the crystal. J. Chem.

Phys. 2012, 137, 184702−1−184702−9.

(

4) Schneemann, A.; Bon, V.; Schwedler, I.; Senkovska, I.; Kaskel, S.;

Fischer, R. A. Flexible metal-organic frameworks. Chem. Soc. Rev. 2014,

4

3, 6062−6096.

(5) Costantino, F.; Ienco, A.; Gentili, P. L.; Presciutti, F. Synthesis, X-

ray Powder Structure, and Photophysical Properties of Three New

Ce(III) Sulfate-Diaminotetraphosphonate-Based Coordination Poly-

mers. Cryst. Growth Des. 2010, 10, 4831−4838.

6) Mendes, R. F.; Paz, F. A. A. Transforming metal-organic

frameworks into functional materials. Inorg. Chem. Front. 2015, 2,

95−509.

7) Chang, Z.; Yang, D. H.; Xu, J.; Hu, T. L.; Bu, X. H. Flexible

5

2

0

.5(MeOH) (4), an isotypical network with 2. Remarkably,

the same behavior was not observed when 3 was simply

exposed to water, even at high temperatures, with only a partial

rehydration being observed. The reasons for such remain

unknown to date.

(

4

(

Metal-Organic Frameworks: Recent Advances and Potential Applica-

tions. Adv. Mater. 2015, 27, 5432−5441.

ASSOCIATED CONTENT

Supporting Information

The Supporting Information is available free of charge on the

ACS Publications website at DOI: 10.1021/acs.inorg-

chem.6b02199.

■

*

S

(8) Zheng, T.; Clemente-Juan, J. M.; Ma, J.; Dong, L.; Bao, S. S.;

Huang, J.; Coronado, E.; Zheng, L. M. Breathing Effect in a Cobalt

Phosphonate upon Dehydration/Rehydration: A Single-Crystal-to-

Single-Crystal Study. Chem. - Eur. J. 2013, 19, 16394−16402.

(

9) Kitagawa, S.; Kitaura, R.; Noro, S. Functional porous

Crystal structure data for 1 (CIF )

Crystal structure data for 2 (CIF )

Crystal structure data for 3 (CIF )

Structural characterization details for 1−3 and L′ and

additional data (PDF )

coordination polymers. Angew. Chem., Int. Ed. 2004, 43, 2334−2375.

(10) Fernandez, C. A.; Thallapally, P. K.; McGrail, B. P. Insights into

the Temperature-Dependent ″Breathing″ of a Flexible Fluorinated

Metal-Organic Framework. ChemPhysChem 2012, 13, 3275−3281.

(

11) McKellar, S. C.; Sotelo, J.; Greenaway, A.; Mowat, J. P. S.;

Kvam, O.; Morrison, C. A.; Wright, P. A.; Moggach, S. A. Pore Shape

Modification of a Microporous Metal-Organic Framework Using High

Pressure: Accessing a New Phase with Oversized Guest Molecules.

Chem. Mater. 2016, 28, 466−473.

AUTHOR INFORMATION

Corresponding Author

E-mail: ﬁ lipe.paz@ua.pt. Fax: (+351) 234 401470. Tel:

+351) 234 370200 (ext 23553).

■

(12) Meilikhov, M.; Yusenko, K.; Fischer, R. A. Incorporation of

*

metallocenes into the channel structured Metal-Organic Frameworks

MIL-53(Al) and MIL-47(V). Dalton Trans. 2010, 39, 10990−10999.

(13) Ferrando-Soria, J.; Ruiz-Garcia, R.; Cano, J.; Stiriba, S. E.;

Vallejo, J.; Castro, I.; Julve, M.; Lloret, F.; Amoros, P.; Pasan, J.; Ruiz-

Perez, C.; Journaux, Y.; Pardo, E. Reversible Solvatomagnetic

Switching in a Spongelike Manganese(II)-Copper(II) 3D Open

Framework with a Pillared Square/Octagonal Layer Architecture.

Chem. - Eur. J. 2012, 18, 1608−1617.

(

ORCID

Paula C. Barbosa: 0000-0002-6983-2329

Filipe A. Almeida Paz: 0000-0003-2051-5645

Notes

The authors declare no competing ﬁnancial interest.

(14) Ye, Y. X.; Wu, X. Z.; Yao, Z. Z.; Wu, L.; Cai, Z. T.; Wang, L. H.;

ACKNOWLEDGMENTS

Ma, X. L.; Chen, Q. H.; Zhang, Z. J.; Xiang, S. C. Metal-organic

frameworks with a large breathing effect to host hydroxyl compounds

for high anhydrous proton conductivity over a wide temperature range

from subzero to 125 degrees C. J. Mater. Chem. A 2016, 4, 4062−4070.

■

We wish to thank Fundaca

FCT, Portugal), the European Union, QREN, FEDER

̧

o

̃

para a Cien

̂

cia e a Tecnologia

(

through Programa Operacional Factores de Competitividade

COMPETE), CICECOAveiro Institute of Materials,

POCI-01-0145-FEDER-007679 (FCT ref. UID/CTM/50011/

013), QOPNA (FCT ref. UID/QUI/00062/2013), and CQE

FCT ref. UID/QUI/00100/2013), ﬁnanced by national funds

(

15) Murdock, C. R.; Hughes, B. C.; Lu, Z.; Jenkins, D. M.

(

Approaches for synthesizing breathing MOFs by exploiting dimen-

sional rigidity. Coord. Chem. Rev. 2014, 258, 119−136.

(16) Takamizawa, S. Dynamic Gas-Inclusion in a Single Crystal.

Angew. Chem., Int. Ed. 2015, 54, 7033−7036.

2

(

M

DOI: 10.1021/acs.inorgchem.6b02199

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

(

17) Sanda, S.; Parshamoni, S.; Konar, S. Third-Generation Breathing

(36) Hubschle, C. B.; Sheldrick, G. M.; Dittrich, B. ShelXle: a Qt

graphical user interface for SHELXL. J. Appl. Crystallogr. 2011, 44,

1281−1284.

Metal-Organic Framework with Selective, Stepwise, Reversible, and

Hysteretic Adsorption Properties. Inorg. Chem. 2013, 52, 12866−

12868.

(37) Brandenburg, K. DIAMOND, Version 3.0a; Crystal Impact GbR:

Bonn, Germany, 1997−2014.

(

18) Bao, S. S.; Li, N. Z.; Taylor, J. M.; Shen, Y.; Kitagawa, H.;

Zheng, L. M. Co-Ca Phosphonate Showing Humidity-Sensitive Single

Crystal to Single Crystal Structural Transformation and Tunable

Proton Conduction Properties. Chem. Mater. 2015, 27, 8116−8125.

(38) Firmino, A. D. G.; Mendes, R. F.; Ananias, D.; Vilela, S. M. F.;

Carlos, L. D.; Tome, J. P. C.; Rocha, J.; Paz, F. A. A. Microwave

́

Synthesis of a Photoluminescent Metal-Organic Framework Based on

a Rigid Tetraphosphonate Linker. Inorg. Chim. Acta 2017, 455, 584−

594.

(39) Macrae, C. F.; Edgington, P. R.; McCabe, P.; Pidcock, E.;

Shields, G. P.; Taylor, R.; Towler, M.; van de Streek, J. Mercury:

visualization and analysis of crystal structures. J. Appl. Crystallogr. 2006,

39, 453−457.

(40) Baur, W. The geometry of polyhedral distortions. Predictive

relationships for the phosphate group. Acta Crystallogr., Sect. B: Struct.

Crystallogr. Cryst. Chem. 1974, 30, 1195−1215.

(

19) Sadakiyo, M.; Yamada, T.; Honda, K.; Matsui, H.; Kitagawa, H.

Control of Crystalline Proton-Conducting Pathways by Water-

Induced Transformations of Hydrogen-Bonding Networks in a

Metal-Organic Framework. J. Am. Chem. Soc. 2014, 136, 7701−7707.

(

20) Costantino, F.; Donnadio, A.; Casciola, M. Survey on the Phase

Transitions and Their Effect on the Ion-Exchange and on the Proton-

Conduction Properties of a Flexible and Robust Zr Phosphonate

Coordination Polymer. Inorg. Chem. 2012, 51, 6992−7000.

(

21) Colodrero, R. M. P.; Papathanasiou, K. E.; Stavgianoudaki, N.;

Olivera-Pastor, P.; Losilla, E. R.; Aranda, M. A. G.; Leon-Reina, L.;

Sanz, J.; Sobrados, I.; Choquesillo-Lazarte, D.; Garcia-Ruiz, J. M.;

Atienzar, P.; Rey, F.; Demadis, K. D.; Cabeza, A. Multifunctional

Luminescent and Proton-Conducting Lanthanide Carboxyphospho-

nate Open-Framework Hybrids Exhibiting Crystalline-to-Amorphous-

to-Crystalline Transformations. Chem. Mater. 2012, 24, 3780−3792.

(41) Silva, P.; Vieira, F.; Gomes, A. C.; Ananias, D.; Fernandes, J. A.;

Bruno, S. M.; Soares, R.; Valente, A. A.; Rocha, J.; Paz, F. A. A.

Thermal Transformation of a Layered Multifunctional Network into a

Metal-Organic Framework Based on a Polymeric Organic Linker. J.

Am. Chem. Soc. 2011, 133, 15120−15138.

(42) Socrates, G. Infrared and raman characteristic group frequencies:

tables and charts; John Wiley & Sons: West Sussex, 2007.

(43) Zhang, J.; Zheng, B.; Zhao, T. T.; Li, G. H.; Huo, Q. S.; Liu, Y.

L. Topological Diversities and Luminescent Properties of Lanthanide

Metal-Organic Frameworks Based on a Tetracarboxylate Ligand. Cryst.

Growth Des. 2014, 14, 2394−2400.

(44) Conolly, M. E.; Kersting, F.; Dollery, C. T. The Clinical

Pharmacology of Beta-Adrenoceptor-Blocking Drugs. Prog. Cardiovasc.

Dis. 1976, 19, 203−234.

(45) Decree, J.; Geukens, H.; Leempoels, J.; Verhaegen, H.

Haemodynamic effects in man during exercise of a single oral dose

of narbivolol (R 67555), a new beta-1-adrenoceptor blocking agent: A

comparative study with atenolol, pindolol, and propranolol. Drug Dev.

Res. 1986, 8, 109−117.

(46) Jacobsen, E. N. Asymmetric catalysis of epoxide ring opening

reactions. Acc. Chem. Res. 2000, 33, 421−431.

(

22) Colodrero, R. M. P.; Olivera-Pastor, P.; Losilla, E. R.; Aranda,

M. A. G.; Leon-Reina, L.; Papadaki, M.; McKinlay, A. C.; Morris, R. E.;

Demadis, K. D.; Cabeza, A. Multifunctional lanthanum tetraphosph-

onates: Flexible, ultramicroporous and proton-conducting hybrid

frameworks. Dalton Trans. 2012, 41, 4045−4051.

(

23) Arinez-Soriano, J.; Albalad, J.; Vila-Parrondo, C.; Perez-Carvajal,

J.; Rodriguez-Hermida, S.; Cabeza, A.; Juanhuix, J.; Imaz, I.; Maspoch,

D. Single-crystal and humidity-controlled powder diffraction study of

the breathing effect in a metal-organic framework upon water

adsorption/desorption. Chem. Commun. 2016, 52, 7229−7232.

(

24) Chen, Z. X.; Ling, Y.; Yang, H. Y.; Guo, Y. F.; Weng, L. H.;

Zhou, Y. M. Two-step synthesis, structure and adsorption property of

a dynamic zinc phosphonocarboxylate framework. CrystEngComm

2

(

011, 13, 3378−3382.

25) Rueff, J. M.; Perez, O.; Pautrat, A.; Barrier, N.; Hix, G. B.;

Hernot, S.; Couthon-Gourves, H.; Jaffres, P. A. Structural Study of

Hydrated/Dehydrated Manganese Thiophene-2,5-diphosphonate

Metal Organic Frameworks, Mn-2(O3P-C4H2S-PO3)center dot

(47) Joossens, J.; Van der Veken, P.; Lambeir, A. M.; Augustyns, K.;

Haemers, A. Development of irreversible diphenyl phosphonate

inhibitors for urokinase plasminogen activator. J. Med. Chem. 2004,

47, 2411−2413.

2

(

H(2)O. Inorg. Chem. 2012, 51, 10251−10261.

26) Shimizu, G. K. H. Assembly of metal ions and ligands with

(48) Young, R. R.; Growdon, J. H.; Shahani, B. T. BETA-

ADRENERGIC MECHANISMS IN ACTION TREMOR. N. Engl. J.

Med. 1975, 293, 950−953.

adaptable coordinative tendencies as a route to functional metal-

organic solids. J. Solid State Chem. 2005, 178, 2519−2526.

(

27) Taddei, M.; Costantino, F.; Ienco, A.; Comotti, A.; Dau, P. V.;

(49) Stead, P.; Marley, H.; Mahmoudian, M.; Webb, G.; Noble, D.;

Ip, Y. T.; Piga, E.; Rossi, T.; Roberts, S.; Dawson, M. J. Efficient

procedures for the large-scale preparation of (1S,2S)-trans-2-

methoxycyclohexanol, a key chiral intermediate in the synthesis of

tricyclic beta-lactam antibiotics. Tetrahedron: Asymmetry 1996, 7,

2247−2250.

Cohen, S. M. Synthesis, breathing, and gas sorption study of the first

isoreticular mixed-linker phosphonate based metal-organic frame-

works. Chem. Commun. 2013, 49, 1315−1317.

(

28) Zheng, T.; Cai, Z. S.; Nie, W. X.; Ren, M.; Bao, S. S.; Zheng, L.

M. Modulating the microporosity of cobalt phosphonates via

positional isomerism of co-linkers. CrystEngComm 2015, 17, 8926−

(50) Mendes, R. F.; Silva, P.; Antunes, M. M.; Valente, A. A.; Paz, F.

A. A. Sustainable synthesis of a catalytic active one-dimensional

lanthanide-organic coordination polymer. Chem. Commun. 2015, 51,

10807−10810.

8932.

(

29) Kirai, N.; Yamamoto, Y. Homocoupling of Arylboronic Acids

Catalyzed by 1,10-Phenanthroline-Ligated Copper Complexes in Air.

Eur. J. Org. Chem. 2009, 2009, 1864−1867.

(51) Vilela, S. M. F.; Ananias, D.; Fernandes, J. A.; Silva, P.; Gomes,

(

30) Kottke, T.; Stalke, D. Crystal handling at low temperatures. J.

́

A. C.; Silva, N. J. O.; Rodrigues, M. O.; Tome, J. P. C.; Valente, A. A.;

Appl. Crystallogr. 1993, 26, 615−619.

31) APEX2 Data Collection Software Version 2.1-RC13; Bruker AXS:

Delft, The Netherlands, 2006.

Madison, WI, USA, 1997−2012.

33) Sheldrick, G. M. SADABS 2012/1; Bruker AXS Area Detector

Scaling and Absorption Correction: Madison, WI, USA, 2012.

34) Sheldrick, G. M. A short history of SHELX. Acta Crystallogr.,

Sect. A: Found. Crystallogr. 2008, 64, 112−122.

35) Sheldrick, G. M., SHELXL Version 2014, Program for Crystal

Structure Reﬁnement; 2014.

Ribeiro-Claro, P.; Carlos, L. D.; Rocha, J.; Paz, F. A. A. Multifunctional

micro- and nanosized metal-organic frameworks assembled from

bisphosphonates and lanthanides. J. Mater. Chem. C 2014, 2, 3311−

3327.

(

(52) Biswas, S.; Maes, M.; Dhakshinamoorthy, A.; Feyand, M.; De

Vos, D. E.; Garcia, H.; Stock, N. Fuel purification, Lewis acid and

aerobic oxidation catalysis performed by a microporous Co-BTT

(BTT³= 1,3,5-benzenetristetrazolate) framework having coordina-

tively unsaturated sites. J. Mater. Chem. 2012, 22, 10200−10209.

(53) Dhakshinamoorthy, A.; Alvaro, M.; Garcia, H. Metal-Organic

Frameworks as Efficient Heterogeneous Catalysts for the Regiose-

(

‑

(

N

DOI: 10.1021/acs.inorgchem.6b02199

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

2

‑

lective Ring Opening of Epoxides. Chem. - Eur. J. 2010, 16, 8530−

Cyclic Ketones on SO /SnO -Fe O Solid Acid Catalysts. Acta Phys.-

4 2 2 3

8536.

Chim. Sin. 2012, 28, 2148−2154.

(

54) Jiang, D.; Mallat, T.; Krumeich, F.; Baiker, A. Copper-based

(73) Liu, L.; Zhao, Y. C.; Gan, S.; Liang, X. Z.; Yang, J. G.; He, M. Y.

Acetalization of carbonyl compounds with 2,2,4-trimethyl-1,3-

pentanedio catalyzed by novel carbon based solid acid catalyst. J.

Nat. Gas Chem. 2008, 17, 149−152.

metal-organic framework for the facile ring-opening of epoxides. J.

Catal. 2008, 257, 390−395.

(

55) Jiang, D. M.; Urakawa, A.; Yulikov, M.; Mallat, T.; Jeschke, G.;

Baiker, A. Size Selectivity of a Copper Metal-Organic Framework and

Origin of Catalytic Activity in Epoxide Alcoholysis. Chem. - Eur. J.

(

74) Gao, S.; Liang, X. Z.; Wang, W. J.; Cheng, W. P.; Yang, J. G.

High efficient acetalization of carbonyl compounds with diols

catalyzed by novel carbon-based solid strong acid catalyst. Chin. Sci.

Bull. 2007, 52, 2892−2895.

75) Patwardhan, S. A.; Dev, S. Amberlyst-15, a Superior Catalyst for

the Preparation of Enol Ethers and Acetals. Synthesis 1974, 1974, 348−

49.

76) Stenberg, V. I.; Kubik, D. A. CATALYTIC DEHYDRATOR -

SIMPLIFIED ISOLATION PROCEDURE FOR ACETALS AND

KETALS. J. Org. Chem. 1974, 39, 2815−2816.

77) Zhang, F. M.; Shi, J.; Jin, Y.; Fu, Y. H.; Zhong, Y. J.; Zhu, W. D.

2

(

009, 15, 12255−12262.

56) Silva, P.; Ananias, D.; Bruno, S. M.; Valente, A. A.; Carlos, L. D.;

Rocha, J.; Paz, F. A. A. Photoluminescent Metal-Organic Frameworks -

Rapid Preparation, Catalytic Activity, and Framework Relationships.

Eur. J. Inorg. Chem. 2013, 2013, 5576−5591.

(

3

(

57) Tanaka, K.; Otani, K. Asymmetric alcoholytic kinetic resolution

of styrene oxide catalysed by chiral metal-organic framework crystals.

New J. Chem. 2010, 34, 2389−2391.

(

58) Vilela, S. M. F.; Ananias, D.; Gomes, A. C.; Valente, A. A.;

(

́

Carlos, L. D.; Cavaleiro, J. A. S.; Rocha, J.; Tome, J. P. C.; Paz, F. A. A.

Multi-functional metal-organic frameworks assembled from a tripodal

Facile synthesis of MIL-100(Fe) under HF-free conditions and its

application in the acetalization of aldehydes with diols. Chem. Eng. J.

organic linker. J. Mater. Chem. 2012, 22, 18354−18371.

2

(

015, 259, 183−190.

(

59) Vilela, S. M. F.; Firmino, A. D. G.; Mendes, R. F.; Fernandes, J.

78) Jin, Y.; Shi, J.; Zhang, F. M.; Zhong, Y. J.; Zhu, W. D. Synthesis

of sulfonic acid-functionalized MIL-101 for acetalization of aldehydes

with diols. J. Mol. Catal. A: Chem. 2014, 383, 167−171.

79) Ren, Y. W.; Liang, J. X.; Lu, J. X.; Cai, B. W.; Shi, D. B.; Qi, C.

A.; Ananias, D.; Valente, A. A.; Ott, H.; Carlos, L. D.; Rocha, J.; Tome,

́

J. P. C.; Paz, F. A. A. Lanthanide-polyphosphonate coordination

polymers combining catalytic and photoluminescence properties.

Chem. Commun. 2013, 49, 6400−6402.

(

R.; Jiang, H. F.; Chen, J.; Zheng, D. 1,4-Phenylenediacetate-Based Ln

MOFs - Synthesis, Structures, Luminescence, and Catalytic Activity.

Eur. J. Inorg. Chem. 2011, 2011, 4369−4376.

(

60) Wee, L. H.; Bonino, F.; Lamberti, C.; Bordiga, S.; Martens, J. A.

Cr-MIL-101 encapsulated Keggin phosphotungstic acid as active

nanomaterial for catalysing the alcoholysis of styrene oxide. Green

Chem. 2014, 16, 1351−1357.

(

80) Dikhtiarenko, A.; Khainakov, S. A.; de Pedro, I.; Blanco, J. A.;

Garcia, J. R.; Gimeno, J. Series of 2D Heterometallic Coordination

Polymers Based on Ruthenium(III) Oxalate Building Units: Synthesis,

Structure, and Catalytic and Magnetic Properties. Inorg. Chem. 2013,

52, 3933−3941.

(

61) Wee, L. H.; Lohe, M. R.; Janssens, N.; Kaskel, S.; Martens, J. A.

Fine tuning of the metal-organic framework Cu (BTC) HKUST-1

3

2

crystal size in the 100 nm to 5 micron range. J. Mater. Chem. 2012, 22,

3742−13746.

62) Zhou, Y. X.; Chen, Y. Z.; Hu, Y. L.; Huang, G.; Yu, S. H.; Jiang,

1

(

(81) Bromberg, L.; Hatton, T. A. Aldehyde-Alcohol Reactions

Catalyzed under Mild Conditions by Chromium(III) Terephthalate

Metal Organic Framework (MIL-101) and Phosphotungstic Acid

Composites. ACS Appl. Mater. Interfaces 2011, 3, 4756−4764.

(82) Herbst, A.; Khutia, A.; Janiak, C. Bronsted Instead of Lewis

Acidity in Functionalized MIL-101Cr MOFs for Efficient Heteroge-

neous (nano-MOF) Catalysis in the Condensation Reaction of

Aldehydes with Alcohols. Inorg. Chem. 2014, 53, 7319−7333.

H. L. MIL-101-SO3H: A Highly Efficient Bronsted Acid Catalyst for

Heterogeneous Alcoholysis of Epoxides under Ambient Conditions.

Chem. - Eur. J. 2014, 20, 14976−14980.

(

63) Zu, D. D.; Lu, L.; Liu, X. Q.; Zhang, D. Y.; Sun, L. B. Improving

Hydrothermal Stability and Catalytic Activity of Metal-Organic

Frameworks by Graphite Oxide Incorporation. J. Phys. Chem. C

2

(

014, 118, 19910−19917.

64) Wiles, C.; Watts, P.; Haswell, S. J. Acid-catalysed synthesis and

(

83) Timofeeva, M. N.; Panchenko, V. N.; Jun, J. W.; Hasan, Z.;

deprotection of dimethyl acetals in a miniaturised electroosmotic flow

Matrosova, M. M.; Jhung, S. H. Effects of linker substitution on

catalytic properties of porous zirconium terephthalate UiO-66 in

acetalization of benzaldehyde with methanol. Appl. Catal., A 2014,

reactor. Tetrahedron 2005, 61, 5209−5217.

(

65) Ajaikumar, S.; Pandurangan, A. Reaction of benzaldehyde with

various aliphatic glycols in the presence of hydrophobic Al-MCM-41:

A convenient synthesis of cyclic acetals. J. Mol. Catal. A: Chem. 2008,

4

(

71, 91−97.

84) Wang, P.; Li, H.; Gao, Q.; Li, P. Z.; Yao, X.; Bai, L. Y.; Nguyen,

2

(

90, 35−43.

66) Elliot, A. J. 1,3-Dioxolane Polymers in Comprehensive Heterocyclic

Polymers; Elliot, A. J., Ed.; Pergamon Press: Oxford, U.K., 1984; Vol. 6.

67) Bauer, K.; Garbe, D.; Surburg, H. Common Fragrance and Flavor

K. T.; Zou, R. Q.; Zhao, Y. L. Fabrication of novel hybrid nanoflowers

from boron nitride nanosheets and metal-organic frameworks: a solid

acid catalyst with enhanced catalytic performance. J. Mater. Chem. A

014, 2, 18731−18735.

85) Dhakshinamoorthy, A.; Alvaro, M.; Garcia, H. Metal Organic

Frameworks as Solid Acid Catalysts for Acetalization of Aldehydes

with Methanol. Adv. Synth. Catal. 2010, 352, 3022−3030.

86) Tang, J.; Oka, T. Infrared Spectroscopy of H O : The ν

Fundamental Band. J. Mol. Spectrosc. 1999, 196, 120−130.

87) Bhattacharya, S.; Gnanavel, M.; Bhattacharyya, A. J.; Natarajan,

S. Organization of Mn-Clusters in pcu and bcu Networks: Synthesis,

Structure, and Properties. Cryst. Growth Des. 2014, 14, 310−325.

88) Tominaka, S.; Coudert, F. X.; Dao, T. D.; Nagao, T.; Cheetham,

A. K. Insulator-to-Proton-Conductor Transition in a Dense Metal-

(

2

(

Materials: Preparation and Uses; Fourth, Completely Revised Edition;

John Wiley & Sons, Inc.: New York, USA, 2001.

(

68) Wu, S. S.; Dai, W. L.; Yin, S. F.; Li, W. S.; Au, C. T. Bismuth

subnitrate as an efficient heterogeneous catalyst for acetalization and

ketalization of carbonyl compounds with diols. Catal. Lett. 2008, 124,

+

(

3

1

(

27−132.

69) Clode, D. M. Carbohydrate cyclic acetal formation and

migration. Chem. Rev. 1979, 79, 491−513.

70) Liu, T. T.; Fu, W. Q.; Zheng, X.; Jiang, J.; Hu, M. L.; Tang, T.

(

D. Zeolite nanofiber assemblies as acid catalysts with high activity for

the acetalization of carbonyl compounds with alcohols. RSC Adv.

Organic Framework. J. Am. Chem. Soc. 2015, 137, 6428−6431.

89) Bazaga-Garcia, M.; Colodrero, R. M. P.; Papadaki, M.;

2

(

014, 4, 18217−18221.

(

71) Sudarsanam, P.; Mallesham, B.; Prasad, A. N.; Reddy, P. S.;

Garczarek, P.; Zon, J.; Olivera-Pastor, P.; Losilla, E. R.; Leon-Reina,

L.; Aranda, M. A. G.; Choquesillo-Lazarte, D.; Demadis, K. D.; Cabeza,

A. Guest Molecule-Responsive Functional Calcium Phosphonate

Frameworks for Tuned Proton Conductivity. J. Am. Chem. Soc.

2014, 136, 5731−5739.

Reddy, B. M. Synthesis of bio-additive fuels from acetalization of

glycerol with benzaldehyde over molybdenum promoted green solid

acid catalysts. Fuel Process. Technol. 2013, 106, 539−545.

(

72) Yang, Z. W.; Chen, L. N.; Hong, W.; Kang, R. X.; Wang, J.; Jia,

N.; Zhao, L.; Ma, H. C. Baeyer-Villiger Oxidation and Acetalization of

O

DOI: 10.1021/acs.inorgchem.6b02199

Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

Article

(

90) Ramaswamy, P.; Wong, N. E.; Shimizu, G. K. H. MOFs as

proton conductors - challenges and opportunities. Chem. Soc. Rev.

014, 43, 5913−5932.

91) Kim, S.; Dawson, K. W.; Gelfand, B. S.; Taylor, J. M.; Shimizu,

2

(

G. K. H. Enhancing Proton Conduction in a Metal-Organic

Framework by Isomorphous Ligand Replacement. J. Am. Chem. Soc.

2

(

013, 135, 963−966.

92) Nagarkar, S. S.; Unni, S. M.; Sharma, A.; Kurungot, S.; Ghosh, S.

K. Two-in-One: Inherent Anhydrous and Water-Assisted High Proton

Conduction in a 3D Metal-Organic Framework. Angew. Chem., Int. Ed.

2

(

014, 53, 2638−2642.

93) Ponomareva, V. G.; Kovalenko, K. A.; Chupakhin, A. P.;

Dybtsev, D. N.; Shutova, E. S.; Fedin, V. P. Imparting High Proton

Conductivity to a Metal-Organic Framework Material by Controlled

Acid Impregnation. J. Am. Chem. Soc. 2012, 134, 15640−15643.

(

94) Yoon, M.; Suh, K.; Natarajan, S.; Kim, K. Proton Conduction in

Metal-Organic Frameworks and Related Modularly Built Porous

Solids. Angew. Chem., Int. Ed. 2013, 52, 2688−2700.

(

95) Boldog, I.; Domasevitch, K. V.; Baburin, I. A.; Ott, H.; Gil-

Hernandez, B.; Sanchiz, J.; Janiak, C. A rare alb-4,8-Cmce metal-

coordination network based on tetrazolate and phosphonate function-

alized 1,3,5,7-tetraphenyladamantane. CrystEngComm 2013, 15, 1235−

1243.

(

96) Plabst, M.; Bein, T. 1,4-Phenylenebis(methylidyne)tetrakis-

phosphonic acid): A New Building Block in Metal Organic

Framework Synthesis. Inorg. Chem. 2009, 48, 4331−4341.

97) Taylor, J. M.; Dawson, K. W.; Shimizu, G. K. H. A Water-Stable

(

Metal-Organic Framework with Highly Acidic Pores for Proton-

Conducting Applications. J. Am. Chem. Soc. 2013, 135, 1193−1196.

(

98) Taylor, J. M.; Mahmoudkhani, A. H.; Shimizu, G. K. H. A

tetrahedral organophosphonate as a linker for a microporous copper

framework. Angew. Chem., Int. Ed. 2007, 46, 795−798.

(

99) Vasylyev, M. V.; Wachtel, E. J.; Popovitz-Biro, R.; Neumann, R.

Titanium phosphonate porous materials constructed from dendritic

tetraphosphonates. Chem. - Eur. J. 2006, 12, 3507−3514.

(

100) Ying, S. M.; Mao, J. G. Introducing a second ligand: New route

to luminescent lanthanide polyphosphonates. Cryst. Growth Des. 2006,

, 964−968.

101) Janicki, R.; Mondry, A. Relationships Between Structure and

6

(

3+

Spectroscopic Properties of Nd Ethylenediaminetetramethylene-

phosphonates and Ethylenediaminetetraacetates. Eur. J. Inorg. Chem.

2

(

013, 2013, 3429−3438.

102) Janicki, R.; Monteil, M.; Lecouvey, M.; Mondry, A. Relations

3+

between structure and physicooptical properties of Eu and Tb

tetraphosphonates. Opt. Mater. 2013, 36, 259−264.

P

DOI: 10.1021/acs.inorgchem.6b02199

Inorg. Chem. XXXX, XXX, XXX−XXX

Article Doi

Robust Multifunctional Yttrium-Based Metal-Organic Frameworks with Breathing Effect

DOI: 10.1021/acs.inorgchem.6b02199

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Article abstract of DOI:10.1021/acs.inorgchem.6b02199

Full text of DOI:10.1021/acs.inorgchem.6b02199

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