Single crystal to single crystal (SC-to-SC) transformation from a nonporous to porous metal-organic framework and its application potential in gas adsorption and Suzuki coupling reaction through postmodification

Article abstract of DOI:10.1002/chem.201405684

A new amino-functionalized strontium-carboxylate-based metal-organic framework (MOF) has been synthesized that undergoes single crystal to single crystal (SC-to-SC) transformation upon desolvation. Both structures have been characterized by single-crystal X-ray analysis. The desolvated structure shows an interesting 3D porous structure with pendent ￡NH₂ groups inside the pore wall, whereas the solvated compound possesses a nonporous structure with DMF molecules on the metal centers. The amino group was postmodified through Schiff base condensation by pyridine-2-carboxaldehyde and palladium was anchored on that site. The modified framework has been utilized for the Suzuki cross-coupling reaction. The compound shows high activity towards the C￡C cross-coupling reaction with good yields and turnover frequencies. Gas adsorption studies showed that the desolvated compound had permanent porosity and was microporous in nature with a BET surface area of 2052 m² g^-1. The material also possesses good CO₂ (8 wt %) and H₂ (1.87 wt %) adsorption capabilities.

Full text of DOI:10.1002/chem.201405684

DOI: 10.1002/chem.201405684
Full Paper
&
Heterogeneous Catalysis
Single Crystal to Single Crystal (SC-to-SC) Transformation from
a Nonporous to Porous Metal–Organic Framework and Its
Application Potential in Gas Adsorption and Suzuki Coupling
Reaction through Postmodification
Rupam Sen,*[a, c] Debraj Saha,[b] Subratanath Koner,[b] Paula Brand¼o,[a] and Zhi Lin*[a]
Abstract: A new amino-functionalized strontium–carboxyl-
ate-based metal–organic framework (MOF) has been
synthesized that undergoes single crystal to single crystal
(SC-to-SC) transformation upon desolvation. Both structures
have been characterized by single-crystal X-ray analysis. The
desolvated structure shows an interesting 3D porous struc-
ture with pendent ꢀNH2 groups inside the pore wall, where-
as the solvated compound possesses a nonporous structure
with DMF molecules on the metal centers. The amino group
was postmodified through Schiff base condensation by
pyridine-2-carboxaldehyde and palladium was anchored on
that site. The modified framework has been utilized for the
Suzuki cross-coupling reaction. The compound shows high
activity towards the CꢀC cross-coupling reaction with good
yields and turnover frequencies. Gas adsorption studies
showed that the desolvated compound had permanent po-
rosity and was microporous in nature with a BET surface
area of 2052 m2 gꢀ1. The material also possesses good CO2
(8 wt%) and H2 (1.87 wt%) adsorption capabilities.
Introduction
is a convenient and unique tool to produce MOFs with novel
applicability. Since the evolution of the isoreticular synthesis of
MOFs, syntheses by modulating the bridging ligands are now
of paramount interest to synthetic inorganic chemists.[4] It is
worth mentioning that MOFs with large pore and functionaliz-
able bridging arms are of wide interest due to their varied ap-
plications from catalysis to gas adsorption. It is well reported
that bifunctional dicarboxylates serve to bridge various metal
ions, producing many highly porous and catalytically active
frameworks.[5] By tuning the porous channel, one can rational-
ize the adsorption and catalytic properties within the pores of
materials.
Rapid development has been achieved on the synthesis and
application of metal–organic frameworks (MOFs) during the
last decade. Much effort has been invested in the rational
design of MOF materials in the fields of gas adsorption and
storage, catalysis, and magnetic material synthesis.[1–3] Many
different pathways have been adopted to produce different
MOFs based on their applications. Among the different
strategies used, postsynthetic modification (PSM) of the MOFs
[a] Dr. R. Sen, Dr. P. Brand¼o, Dr. Z. Lin
Department of Chemistry, CICECO, University of Aveiro
3810-193 Aveiro (Portugal)
In catalytic reactions, palladium-catalyzed cross-coupling is
one of the most powerful tools for the formation of CꢀC
bonds in organic synthesis.[6] There are many approaches, in-
cluding Suzuki, Stille, and Sonogashira, that are well recog-
nized and highly applicable in organic synthesis.[7] Among
them, the Suzuki coupling reaction has become a mainstay in
modern synthetic organic chemistry for the preparation of
biaryl compounds in a feasible manner, and researchers are
still engaged in developing this field to make it more cost
effective and truly heterogeneous.[8] The coupling products of
these reactions have been employed in a variety of applica-
tions as intermediates in the preparation of functional materi-
als, natural products, and bioactive compounds.[9] It is worth
mentioning that recently scientists have used this technique to
produce different bridging ligands to construct porous and
functionalizable MOFs.[10] Although homogeneous catalytic sys-
tems are known to exhibit better activity than heterogeneous
systems, for large-scale applications in liquid-phase reactions
E-mail: rupamsen1@yahoo.com
zlin@ua.pt
[b] D. Saha, Dr. S. Koner
Department of Chemistry, Jadavpur University
Kolkata 700 032 (India)
[c] Dr. R. Sen
Present address: Institute for Materials Chemistry and Engineering
Kyushu University, Kasuga, Fukuoka 816-8580 (Japan)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201405684. It contains detailed experimen-
tal information; crystal structure refinement parameters and tables for
bond distances and angles; cifs; a scheme for the three-phase and blank
tests; the solid-state UV/Vis spectrum of the catalyst; powder XRD patterns
of Sr-MOF-1, Sr-MOF-1-PI, and Sr-MOF-1-PI-Pd, TG analysis and differential
thermal analysis profiles of Sr-MOF-1; SEM images and X-ray elemental
mapping of Sr-MOF-1, Sr-MOF-1-PI, Sr-MOF-1-PI-Pd, and the recovered cat-
alyst; powder XRD patterns; gas adsorption studies of virgin and recovered
catalyst, plots for the comparison of the percentage conversion in CꢀC cou-
1
pling reactions with different amounts of SHꢀSiO2; and H NMR spectra of
all products of known compounds.
Chem. Eur. J. 2015, 21, 1 – 11
1
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
they causes greater difficulties, such as purification of the final
product, recycling of the catalyst, and deactivation of catalyst
through aggregation of inactive palladium particles. Further re-
moval of palladium from organic products at the end of the re-
action is highly desirable because of its high cost and toxicity.
Hence, the development of heterogeneous systems in which
the metal is grafted onto inorganic or organic supports has
attracted attention in recent years.[11]
Recently, a few approaches have been made to use MOFs in
catalysis.[9–13] After the first introduction of PSM by Seo and co-
workers, the field opened up to a new strategy of using MOFs
in catalytic reactions.[12b] In another study, Cohen et al.[12c]
successfully developed the postmodification of IRMOF-3 and
covalently modified the pendant ꢀNH2 linkers to amides by
more than >80%. Since then, many organic reactions have
been used to covalently functionalize MOF backbones.[9–13]
Thus, these MOFs represent a good model system for postsyn-
thetic covalent modification studies. However, heavy-metal-
anchored MOFs are still scarce in this field.[10,14] Therefore, new
strategies to develop such catalytic systems and exploit their
remarkable structural and chemical flexibility deserve to be ex-
plored in more detail. In the course of our continuing investi-
gations into the catalytic uses of MOFs, we have successfully
employed
Figure 1. Single-crystal X-ray structures: a) coordination environment of Sr-
MOF-1’; b) 3D packing diagram of Sr-MOF-1’, showing the DMF molecules
present inside the pores of the MOF; c) coordination environment of Sr-
MOF-1; d) 3D porous structure of Sr-MOF-1 without DMF molecules; and
e) 1D edge-shared chain present in both compounds.
connected by the m links of the ATA ligands in two directions
to generate the 3D framework. The pores of the 3D structure
are filled with DMF molecules and the walls are decorated with
free ꢀNH2 groups (Figure 1b). A solvent-accessible void (SAV)
calculation by PLATON analysis shows no SAV.
layered metal carboxylates and vanadium(IV) hydrogen phos-
phate and lanthanide-based MOFs to catalyze the olefin epoxi-
dation reaction under heterogeneous conditions.[15] Recently,
we developed porous MOF-based catalysts containing alkaline-
earth metals for aldol condensation reactions.[16] In contrast to
those systems, herein, we introduce a novel strontium-based
MOF that is highly thermally and chemically robust, can be
postfunctionalized by covalent modification, and can also be
used for Suzuki cross-coupling reactions by anchoring palladi-
um onto the modified arms. In addition to CꢀC coupling reac-
tions, the structure also possesses permanent porosity and
shows good H2 and CO2 adsorption properties. To the best of
our knowledge, this is the first example of alkaline-earth-based
MOFs for postmodification. It is also the first reported
strontium-based MOF with the highest low pressure H2 and
CO2 adsorption capacities at 77 and 298 K, respectively.
Structural description of Sr-MOF-1
On the other hand, single-crystal X-ray diffraction shows that
the desolvated structure crystallizes in the space group Pnma
with a Z value of four, and possesses an extended porous 3D
framework in which the asymmetric unit contains one Sr atom,
one ATA ligand, and one O2ꢀ ion. The strontium(II) ion is eight-
coordinated and binds six oxygen atoms from the carboxylate
groups belonging to four ATA ligands (four chelating oxygen
atoms O1, O11#, O2, and O21#; two syn–syn m2-carboxylate
1
1
oxygen atoms, O12# and O13#, in which 1#=ꢀ = +x, y, = ꢀz;
2
2
1
2#=ꢀ1+x, y, z; and 3#=ꢀ1+x, = ꢀy, z), and two m2-O bridg-
2
1
1
ing oxide atoms (O8 and O84#, in which 4#=ꢀ = +x, = ꢀy,
2
2
1
= ꢀz; the coordination environment is shown in Figure 1c).
2
The position of the amino nitrogen atom in the benzene ring
of ATA is disordered in two places with half occupancy. Each
ATA anion bonds to four strontium(II) ions with the two car-
boxylate groups. Each carboxylate group chelates to one stron-
tium atom through its oxygen atoms and one of the two
oxygen atoms also bridges to another cation. SrO monocap-
ped pentagonal bipyramids (Figure 1c) share edges to create
an inorganic motif in the form of a zigzag 1D chain running
along the a axis (Figure 1e). These 1D chains are connected by
the m links of the ATA ligands in two directions to generate the
3D framework (Figure 1d) with rhomboidal channels running
along the a axis with a cross section of about 9 ꢁꢂ18 ꢁ. The
SAV value calculated by PLATON analysis was 412.7 ꢁ3, which
was 29% of the unit cell volume. Therefore, channel blocking
in Sr-MOF-1’ probably results from DMF groups extending into
the channels. Simplified topological analysis by TOPOS[17] on
compound Sr-MOF-1 revealed that this compound was a 2-
Results and Discussion
Structural description of Sr-MOF-1’
The compound crystallizes in the space group P21/n with a Z
value of four. This compound possesses an extended 3D struc-
ture. The asymmetric units are formed by one Sr ion, one
amino terephthalate anion (ATA), and one m2-bridged DMF
molecule. In the asymmetric unit, each metal center is a mono-
capped pentagonal bipyramid that shares edges to create an
inorganic motif in the form of a zigzag 1D chain running along
the b axis. The basal plane is formed by five oxygen atoms
(O8, O8#, O15, O15#, O9; in which #=ꢀ = +x, ꢀ = ꢀy, ꢀ = +z)
1
1
1
2
2
2
and the axial sites are fulfilled by oxygen atoms (O1 and O2).
The monocapped position is occupied by O1* (the coordina-
tion environment is shown in Figure 1a). These 1D chains are
&
&
Chem. Eur. J. 2015, 21, 1 – 11
www.chemeurj.org
2
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
mation). The UV/Vis spectrum featured a strong band at l=
410 nm that could be ascribed to the charge-transfer transition
arising from p-electron interactions between the metal and
ligand, which involves ligand to metal electron transfer that is
typical for a Pd–Schiff base complex (Figure S1 in the Support-
ing Information).[19] Other bands appearing in the region at l
ꢁ240 and 300 nm can be attributed to intraligand transitions.
The relatively weak band that appeared in the visible region
for d–d transitions could not be resolved, owing to its very low
extinction coefficient. The FTIR spectra of Sr-MOF-1, Sr-MOF-1-
PI, and Sr-MOF-1-PI-Pd were measured as KBr pellets (Figure 3).
Figure 2. Simplified topological view of Sr-MOF-1, which shows a binodal
4,6-connected net topology.
nodal 4, 6-c 3D net with the Schlꢃfli symbol {32.62.72}{34.42.64.75}
(Figure 2, in which L2ꢀ ligands act as a four-connected node
and Sr(II) centers act as a six-connected node).
PSM of Sr-MOF-1
Sr-MOF-1 is a porous MOF decorated with pendant amine
(ꢀNH2) groups on the walls of the pores. The amine moieties
are not involved in the framework backbone, and therefore,
are available to undergo chemical transformations. The free
ꢀNH2 groups were thus covalently modified through
a
simple condensation reaction to produce a 2-pyridylimine (Rꢀ
N=CꢀC5H4N) moiety, which was useful as a bidentate ligand.
Pyridylimine formation activated the framework towards metal
sequestering, as demonstrated by anchoring PdII to the wall of
Sr-MOF-1. The preparative procedure is summarized in
Scheme 1. To optimize the catalytic efficacy of Sr-MOF-1-PI-Pd,
we controlled the functionalization by varying the amount of
pyridine-2-aldehyde, and subsequently by varying the amount
of palladium chloride in the Schiff base complex. Through this
preparative method, a maximum functionalization of about
52% of the total ꢀNH2 groups was achieved without losing the
framework integrity, whereas palladium complexation by the
Schiff base complex was quantitative. The Schiff base complex
features a square-planar geometry with a cis configuration, as
described earlier.[18] A similar type of ligand arrangement is
expected in this case (Scheme 1).
Figure 3. FTIR spectra of Sr-MOF-1, Sr-MOF-1-PI (after Schiff base formation),
Sr-MOF-1-PI-Pd (after anchoring with Pd), and the recovered catalyst.
The characteristic IR vibration bands for free ꢀNH2 groups pres-
ent in the framework of Sr-MOF-1 appeared in the range of
n˜ =3300–3460 and 1500–1600 cmꢀ1. A moderately intense
band for NꢀH stretching of Sr-MOF-1 appeared at n˜
ꢁ3457 cmꢀ1, whereas the relatively strong band that appeared
at n˜ =1555 cmꢀ1 could be ascribed to the bending vibration
mode of the ꢀNH2 groups. The IR spectrum of Sr-MOF-1-PI
shows a new band at n˜ =1652 cmꢀ1, in addition to the above-
mentioned bands. This band can be ascribed to the vibration
band for the azomethine group (>C=Nꢀ). The appearance of
this new band in the IR spectrum of Sr-MOF-1-PI, which was
absent in the case of Sr-MOF-1, clearly indicates that the Sr-
MOF-1 framework has been organically modified, as shown in
Scheme 1. It should be noted here that only 52% of ꢀNH2
groups undergo functionaliza-
Spectroscopic studies
The electronic spectrum of the catalyst Sr-MOF-1-PI-Pd was
measured in the solid state (Figure S1 in the Supporting Infor-
tion upon treatment with pyri-
dine-2-aldehyde to form the
Schiff base moiety in the frame-
work (see above). In Sr-MOF-1-
PI-Pd, the vibration bands for
the azomethine group shift to
a lower frequency range, which
clearly indicates coordination of
the azomethine nitrogen atom
with palladium(II). Characteristic
Scheme 1. PSM procedure for obtaining MOFs containing a PdII Schiff base complex.
bands for the carboxylato vibra-
Chem. Eur. J. 2015, 21, 1 – 11
www.chemeurj.org
3
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
tion have appeared in the range n˜ =1250–1450 cmꢀ1 in all
Gas sorption studies
samples.
The nitrogen sorption isotherms of Sr-MOF-1, Sr-MOF-1-PI,
catalyst Sr-MOF-1-PI-Pd, and the recovered catalyst are
shown in Figure 4 and Figure S8 in the Supporting Information.
Powder XRD studies
Powder XRD patterns of Sr-MOF-1’, Sr-MOF-1, Sr-MOF-1-PI, and
catalyst Sr-MOF-1-PI-Pd were studied (Figures S2 and S3 in the
Supporting Information). A comparison of the powder XRD
patterns of Sr-MOF-1, Sr-MOF-1-PI, and Sr-MOF-1-PI-Pd showed
that the pattern of Sr-MOF-1 was not altered. This clearly
shows that the framework structure of Sr-MOF-1 remained
intact upon organic functionalization and metal complex for-
mation. We also found that Sr-MOF-1 was stable in different
solvents (Figure S4 in the Supporting Information).
Thermal measurements
Thermogravimetric (TG) analysis of Sr-MOF-1’ and Sr-MOF-
1 was performed by using a powdered sample under a nitro-
gen atmosphere in the temperature range from RT to 8008C.
The TG curve indicates that, upon heating, Sr-MOF-1’ starts to
lose coordinated DMF molecules at room temperature and this
is complete at around 608C. The mass loss of 17% corrobo-
rates the theoretical value of 17%. Upon further heating, there
was no mass change up to 3308C, and thereafter, it rapidly
started to lose mass in two continuous steps and was com-
plete at around 5008C. The mass loss seems to be due to con-
tinuous decomposition of the organic ligand present in the
framework. For desolvated Sr-MOF-1, it does not show any
mass loss between room temperature and 3308C, then it also
rapidly starts to lose mass, which is complete at around 6868C,
in two continuous steps and decomposes accordingly. En-
hancement of the end point of decomposition may be due to
greater stability of the desolvated framework (Figure S5 in the
Supporting Information).
Figure 4. Nitrogen sorption isotherms of Sr-MOF-1; Sr-MOF-1-PI, and
Sr-MOF-1-PI-Pd at 77 K.
All materials featured a type II isotherm (according to IUPAC
nomenclature). The BET[20] surface area of the materials was
calculated from isotherms. The pore volume of the samples
was calculated be using DFT methods. A gradual decrease in
the BET surface area and pore volume was observed at each
stage of modification. This is consistent with the fact that or-
ganic fragments or metal complexes occupy the pores upon
modification of the MOF at different stages. Framework Sr-
MOF-1 generates 3D rhombic channels with sizes of 9 ꢁꢂ18 ꢁ,
excluding van der Walls radii. The free void volume of Sr-MOF-
1 is 29%, as estimated by PLATON.[17] The nitrogen sorption
study revealed that the BET surface area of Sr-MOF-1 was
2052 m2 gꢀ1 (Langmuir surface area=2859 m2 gꢀ1
;
pore
volume=1.05 ccgꢀ1). Sr-MOF-1-PI showed a smaller N2 uptake
with a BET surface area of 1808 m2 gꢀ1 (Langmuir surface
area=2578 m2 gꢀ1; pore volume=0.78 ccgꢀ1); this indicates
that a Schiff base formed upon treatment with pyridine-2-alde-
hyde occupied space in the Sr-MOF-1 pores. Sr-MOF-1-PI-Pd
showed the lowest N2 uptake with a BET surface area of
1636 m2 gꢀ1 (Langmuir surface area=2397 m2 gꢀ1) and pore
volume of 0.69 ccgꢀ1; this demonstrates that the metal is
anchored to the framework compound.
SEM and elemental mapping studies
SEM and X-ray elemental mapping were performed on samples
Sr-MOF-1, Sr-MOF-1-PI, and Sr-MOF-1-PI-Pd (Figures S6 and S7
in the Supporting Information). Figure S6 in the Supporting In-
formation displays the morphologies of all compounds. Fig-
ure S7 in the Supporting Information shows the presence of
strontium in compound Sr-MOF-1 and, after it was postmodi-
fied by imine formation, the distribution of strontium ions
within the material was similar. Figure S7c in the Supporting
Information gives the distribution of palladium ions in the
compound after palladium modification, and the distribution
of palladium ions in the material was homogeneous. After the
catalytic reaction, the strontium/palladium distribution in the
compound is very similar to that of the parent material
(Figure S7d in the Supporting Information). These results also
suggest that palladium is not accumulated on the surface of
the materials, but rather homogeneously dispersed.
Recently, many modified MOFs have been developed for
CO2 adsorption based on our environmental concerns.[21] To
enhance adsorption, many techniques have been introduced
to alter the MOF surface or metal nodes, such as introducing
heteroatoms into the ligand systems, as well as anchoring an
alkyl amine to the ligand arm or on the metal centers.
Interactions between the lone pair of nitrogen and CO2 have
been very effective to enhance the gas adsorption ability. To
date, three major classes of nitrogen-functionalized MOFs have
been synthesized: N-heterocycle derivatives, aromatic amine
&
&
Chem. Eur. J. 2015, 21, 1 – 11
www.chemeurj.org
4
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
derivatives, and alkylamine-bearing frameworks.[22] Among the
established framework systems, aromatic amine containing
linkers, and postmodified amino-functionalized MOFs are more
efficient for their expected affinity of amino groups toward
CO2 and generated significant interest in aromatic amine func-
tionalized frameworks.[22–24] Amine functionalization enhanced
the CO2 capacity in a number of other MOFs, including
have been extensively studied in the past decade. Several fac-
tors that influence the hydrogen uptake of porous MOFs, such
as surface area, catenation, ligand functionalization, doping
with alkali metals, and unsaturated metal centers, have been
extensively studied.[25] On the other hand, strontium(II) has
a large coordination number, which varies from seven to ten.
Therefore, it is very difficult to find a highly porous MOF
containing strontium(II) in its metal site. Sr-MOF-1 is the first
reported highly porous strontium(II) MOF, which exhibits the
largest surface area with the highest low-pressure CO2 and H2
uptake among the strontium(II) MOF family.
Ni2(NH2-BDC)2(DABCO)
(BDC=1,4-benzenedicarboxylate,
DABCO=1,4-diazabicyclo[2.2.2]octane), Al(OH)(NH2-BDC), and
In(OH)(NH2-BDC), when comparing their low-pressure capaci-
ties with that of the parent material (Ni2(BDC)2(DABCO),
Al(OH)(BDC), and In(OH)(BDC)).[23e] At 298 K and 1 bar, Sr-MOF-
1 adsorbs approximate 8.0 wt% CO2 (Figure 5), which is signifi-
Catalytic activity studies
Suzuki cross-coupling reaction
The catalytic activity of Sr-MOF-1-PI-Pd in the Suzuki cross-
coupling reaction was first tested between bromobenzene and
phenylboronic acid. Solvents and bases have remarkable
influences on the reactivity of the catalyst in the Suzuki cross-
coupling reaction; the results are summarized in Table 1 (more
Table 1. The effect of solvents and bases on Suzuki cross-coupling
reactions.[a,b]
Entry
Solvent (v/v)
Base
Time
[min]
Yield[c]
[wt%]
Figure 5. Carbon dioxide sorption isotherms of Sr-MOF-1 at 298 K and 1 bar.
1
2
3
4
5
6
7
8
9
10
DMF
DMF
DMF/H2O (4:1)
DMF/H2O (4:2)
DMF/H2O (4:3)
H2O
MeOH
EtOH
EtOH
EtOH/H2O (4:1)
no base
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
no base
K2CO3
K2CO3
90
90
10
20
40
90
90
90
90
90
28
80
100
100
100
36
52
18
68
100
cantly higher than that of its analogous zinc compound
IRMOF-3 (CO2 uptake is about 5.0 wt% at 298 K and
1.1 bar).[23f]
On the other hand, it is noteworthy that Sr-MOF-1 shows
a very good H2 adsorption capability of 1.87 wt% at 77 K and
1 bar (Figure 6), which is significant and comparable to similar
MOF families, for example, IRMOF-3 (the hydrogen uptake is
about 1.42 wt% at 77 K and 1 bar).[25] As a source of energy,
hydrogen is a new hope for our modern civilization to replace
depleted energy sources.[26] The main goal is to develop an on-
board H2 storage system that fulfils successfully the daily need
for fuel.[27] As promising hydrogen storage materials, MOFs
[a] Reaction conditions: aryl halide (3 mmol), phenylboronic acid
(3.3 mmol), base (3 mmol), Sr-MOF-1-PI-Pd catalyst (0.002 g; Pd content:
10.44ꢂ10ꢀ2 mol%, Pd/ArX molar ratio; 0.07:1) in solvent (5 mL) at 808C.
[b] No homocoupled product was observed during the course of the
reaction. [c] Yield determined by GC.
results are given in Table S1 in the Supporting Information).[28]
Preliminary screening of solvents revealed that the presence of
DMF could efficiently catalyze the Suzuki cross-coupling reac-
tion in water. Additionally, in DMF, the rate of reaction is very
fast; however, palladium leaches from the solid catalyst, which
is not desirable from environmental and economic points of
view. Leaching of palladium was diminished with increasing
H2O/DMF ratio. It is well established that leaching of Pd often
occurs in CꢀC coupling reactions if DMF is used as a solvent.[29]
Notably, for a desirable activity of catalyst Sr-MOF-1-PI-Pd can
be achieved by using ethanol instead of DMF. The optimal con-
ditions involved using K2CO3 as a base in 20% aqueous etha-
nol (Table 1, entry 10). Under the same conditions, NaHCO3,
Figure 6. Hydrogen sorption isotherms of Sr-MOF-1 at 77 K and 1 bar.
Chem. Eur. J. 2015, 21, 1 – 11
www.chemeurj.org
5
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
KHCO3, NaOAc·3H2O, KOAc, Na3PO4·12H2O, and K3PO4·3H3O
gave moderate biphenyl yields (Table S1 in the Supporting In-
formation, entries 1–9). Remarkably, when K2CO3 and Na2CO3
were used (Table 1, entry 10, and Table S1 in the Supporting In-
formation, entry 3), good to excellent biphenyl yields were ob-
tained, whereas K2CO3 in water gave only a 36% yield of bi-
phenyl (Table 1, entry 6). The use of trialkylamine or lithium
chloride as a base resulted in a low yield (Table S1 in the Sup-
porting Information, entries 10 and 11). Indeed, K2CO3 in 20%
aqueous ethanol was found to be the best choice, in view of
an almost quantitative biphenyl yield obtained within a
reasonably short reaction time (1.5 h; Table 1, entry 10).
I2 generated from iodobenzene could act as an inhibitor
during the catalytic process.[30b] The Sr-MOF-1-PI-Pd catalyst
was capable of activating chlorobenzene (Table 2, entry 3),
which normally remains unreactive in the CꢀC coupling reac-
tion; however, the yield was much lower in comparison to
some previous reports.[31] Generally, it is difficult to activate
CꢀCl bonds because of their relative inertness.[32] The para-
substituted bromobenzene derivatives with ꢀOH, ꢀOCH3,
ꢀNH2, ꢀCHO, ꢀCOCH3, ꢀNO2, ꢀCOOH, ꢀCN, ꢀCl, and ꢀF groups
generally show enhanced activity in Suzuki reactions. The reac-
tivity of aryl bromides with electron-withdrawing substituents
was higher than that of electron-donating substituents. It is
worth noting that the turnover frequency (TOF) reached about
1437 hꢀ1 in the case of 4-nitrobromobenzene. However, aryl
bromides containing the ꢀCOOH group required a longer reac-
tion time for 100% conversion (from GC analysis) compared
with other electron-withdrawing substituents. This may be due
to a decrease in the basicity of the reaction medium. The che-
moselectivity of the reaction was examined by using bromo-
chlorobenzene (Table 2, entry 12). The sterically hindered
ortho-substituted substrate o-nitrobromobenzene participated
in the coupling reaction to give a good yield of product, 2-ni-
trobiphenyl (Table 2, entry 14). The kinetic profiles of the prog-
ress of catalytic reactions are shown in Figure 7. The rate of
In the Suzuki cross-coupling reaction, the catalytic activities
of Sr-MOF-1-PI-Pd for various substrates were determined at
808C in air by using a suitable solvent (20% aqueous ethanol)
and base (K2CO3). The results are summarized in Table 2.
Table 2. Suzuki cross-coupling reactions catalyzed by Sr-MOF-1-PI-Pd.[a,b]
Entry
R[c]
X
Time
[h]
Yield[d]
[wt%]
TOF[e]
[hꢀ1
]
1
2
3
4
5
6
7
8
H
H
H
I
2.0
1.5
6
1.5
1.5
1.5
1.5
1.5
1
1
3
1.5
1.5
1.5
100
100
25
72
78
82
96
100
100
94
719
958
60
Br
Cl
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
OH
OMe
NH2
CHO
COCH3
NO2
CN
COOH
Cl
F
690
747
785
919
958
1437
1350
354
900
958
862
9
10
11
12
13
14
74
94
100
90
NO2
[a] Reaction conditions: aryl halide (3 mmol), phenylboronic acid
(3.3 mmol), K2CO3 (3 mmol), Sr-MOF-1-PI-Pd catalyst (0.002 g; Pd content:
10.44ꢂ10ꢀ2 mol%) in 20% H2O/EtOH (5 mL) at 808C. [b] Homocoupled
product was obtained only for ArꢀCl at a longer reaction time of 12 h.
[c] All R groups are para substituted, except for entry 14 (R is ortho
substituted). [d] Yield of product isolated/yield determined by GC.
[e] TOF=turnover frequency in units of mol of biaryl per mol of Pd per h.
Figure 7. Kinetic plots for the Suzuki coupling reaction.
product formation increased steadily in the beginning of the
reaction, giving no noticeable induction period. To ascertain if
the coupling reaction was indeed occurring inside the pores of
the catalyst Sr-MOF-1-PI-Pd, we performed a few control ex-
periments with the bulkier substrate 9-bromoanthracene. The
Suzuki reaction with 9-bromoanthracene yielded no coupling
product and remained inactive (Scheme 2). This indicates that
the functionalized pore windows of Sr-MOF-1-PI-Pd do not
allow 9-bromoanthracene or its corresponding product to
diffuse through the pores owing to their larger size.
Among nonsubstituted aryl halides, iodo- and bromobenzene
(Table 2, entries 1 and 2) showed comparable yields, which
were higher than that of chlorobenzene. However, iodoben-
zene required a longer reaction time for 100% conversion
(from GC analysis). Iodobenzene generally shows greater
reactivity than bromobenzene in the cross-coupling reactions.
Nevertheless, there were some exceptions in which reverse
catalytic activity was observed in palladium-nanoparticle-
based catalysts.[30] In a recent study, it was proposed that Iꢀ or
Test for the homocoupling reaction
The homocoupling reaction sometimes features in the Suzuki
reaction.[33] Generally, the homocoupled product originates
&
&
Chem. Eur. J. 2015, 21, 1 – 11
www.chemeurj.org
6
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
Scheme 2. Test for shape selectivity with bromobenzene and 9-bromo-
anthracene. Reaction conditions: aryl halide (3 mmol), phenylboronic acid
(3.3 mmol), base (3 mmol), Sr-MOF-1-PI-Pd catalyst (0.002 g) in 20%
H2O/EtOH (5 mL) at 808C.
Figure 8. Comparison of the catalytic activity of Sr-MOF-1-PI-Pd in the
Suzuki cross-coupling reaction between bromobenzene and phenylboronic
acid in different catalytic cycles.
from homocoupling among the boronic acid derivatives
instead of coupling with the aryl halides. This phenomenon
usually occurs due to the poor reactivity of the aryl halides
and long reaction timescale. We examined this phenomenon
by using PhꢀCl and PhꢀBr with 4-methylphenylboronic acid,
but we did not observe any 4,4’-dimethylbiphenyl when bro-
mobenzene was used, and 4,4’-dimethylbiphenyl was obtained
only in the case of chlorobenzene with longer reaction time
(see the Supporting Information for product analysis). This
result reveals typical behavior for less reactive PhꢀCl, which
corroborates previous results[34] and also supports the results
obtained for cross-coupling reactions.
oughly as mentioned above and dried under vacuum at 1008C
overnight. The recovered catalyst was then subjected to
powder XRD, IR spectral analysis, and gas adsorption studies. A
comparison of the XRD patterns (Figure S3 in the Supporting
Information), IR spectra (Figure 3), and results from gas
adsorption studies (Figure S8 in the Supporting Information) of
the pristine compound and recovered catalyst convincingly
demonstrates that the structural integrity of the compound is
retained after the reactions.
Heterogeneity test
To ascertain that the catalysis was indeed heterogeneous, we
performed a series of tests, as described below.
Separation and catalyst reuse
The catalyst Sr-MOF-1-PI-Pd is not thermal, air, or moisture sen-
sitive and so there is no need to carry out the reaction under
an inert atmosphere. The catalyst is easily recoverable by filtra-
tion and can be reused several times without any loss of cata-
lytic activity. Because 2 mg of solid catalyst is not enough to
recover, reuse, and finally characterize, the catalyst was collect-
ed from independent reactions of the same catalytic cycle and
combined for the recycling study. The Suzuki coupling reaction
was performed with bromobenzene under the same reaction
conditions. After the first cycle of the reaction, the catalyst was
recovered by centrifugation and then washed thoroughly with
diethyl ether, followed by copious amounts of water to
remove base present in the used catalyst, and finally with
dichloromethane. The recovered catalyst was dried under
vacuum at 1008C overnight. Atomic absorption spectrometric
analysis of the recovered catalysts confirmed that the palladi-
um content of Sr-MOF-1-PI-Pd remained the same, even after
its reuse. The performance of the recycled catalyst in the
Suzuki coupling reaction in up to five successive runs is shown
in Figure 8. The catalytic efficacy of the recovered catalyst
remained almost the same in every run.
Hot filtration test[33]
To test whether metal was leaching from the solid catalyst
during the reaction, the liquid phase of the reaction mixture
was collected by filtration at the reaction temperature when
the catalytic reaction (Suzuki) for bromobenzene was 30%
complete and the residual activity of the supernatant solution
was studied. After filtration of the Sr-MOF-1-PI-Pd catalyst from
the batch reactor at the reaction temperature, coupling reac-
tions do not proceed further. Atomic absorption spectrometric
analysis (sensitivity up to 0.001 ppm) of the supernatant
solution of the reaction mixture thus collected by filtration also
confirmed the absence of palladium ions in the liquid phase.
Thus, the results of the hot filtration test suggested that
palladium was not being leached from the solid catalyst
during cross-coupling reactions.
Solid-phase poisoning test
According to Richardson and Jones, the solid-phase poisoning
test is one of the important tests to ascertain the true hetero-
geneity of the palladium-based catalyst in CꢀC coupling reac-
tions.[35] In this test, metal-free mercaptopropyl-functionalized
To check the stability of the catalyst, we characterized the
recovered catalyst. After the catalytic reactions were over, solid
catalyst was recovered by centrifugation and washed thor-
Chem. Eur. J. 2015, 21, 1 – 11
www.chemeurj.org
7
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
silica (in our case SHꢀSiO2) was used as an effective palladium
scavenger that selectively coordinated and deactivated leached
palladium.[35,36] Therefore, cessation of the reaction is expected
if the coupling reaction is catalyzed by palladium species
leached from the solid support. Richardson and Jones also ob-
served that poisoning was effective when the S/Pd molar ratio
was greater than 5.3:1. A comparison of the percentage con-
version in CꢀC coupling reactions (Figure S9 in the Supporting
Information) clearly indicates that the catalytic efficacy of Sr-
MOF-1-PI-Pd was not affected when different amounts of SHꢀ
SiO2 were added to the reaction mixture. In the coupling reac-
tion, the catalyst remained active, even in the presence of
a large excess of SHꢀSiO2. Kinetic profiles of a typical Suzuki
none would have also participated in the above-described
Suzuki reaction. However, this is not the case for the present
catalyst. Therefore, all of these tests convincingly demonstrat-
ed that there was no leaching of Pd species during the Sr-
MOF-1-PI-Pd-catalyzed CꢀC coupling reactions. A blank reac-
tion was also performed, which showed that p-bromoaceto-
phenone was also able to react with phenylboronic acid in the
presence of p-nitrobromobenzene (Scheme S2 in the Support-
ing Information).
In search of MOF-based efficient heterogeneous catalysts for
Suzuki reactions, several attempts have been made, of which
a few deserve particular mention. Suzuki reactions catalyzed
by various palladium-containing heterogeneous catalysts are
coupling reaction in the presence of the poisoning agent SHꢀ given in Table 3. Different solid-supported palladium com-
plexes were reported that catalyzed the Suzuki coupling reac-
tion in environmental friendly water medium under truly heter-
ogeneous conditions and catalysts were reused several times
without any loss of activity.[37] Corma et al. reported the Suzuki
coupling of p-bromoanisole by a palladium-containing MOF in
ethanol at 258C; this yielded p-methoxybiphenyl with high se-
lectivity, but required a longer time (48 h) for a conversion of
87%.[38] Stepnicka et al. studied the Suzuki coupling reaction of
substituted bromobenzene with a reusable palladium catalyst
prepared from mesoporous molecular sieves bearing nitrogen
donor groups with different palladium loadings and, in some
cases, a quantitative yield was obtained in anhydrous ethanol
after 24 h of reaction.[39] Palladium nanoparticles embedded in
a porous sponge-like silica was used as a catalyst in the Suzuki
coupling reaction of p-bromoanisole and phenylboronic acid,
and up to 96% yield was obtained at a higher temperature
(1358C) in DMF. However, in this case, a gradual decrease in
ˇ
ˇ
ˇ
Figure 9. Kinetic profiles for the Suzuki coupling reaction of bromobenzene
with or without SHꢀSiO2 as the solid-phase poison (S/Pd ratio of 500:1).
SiO2 (S/Pd ratio of 500:1) are
Table 3. Suzuki reactions of aryl halides with phenylboronic acid catalyzed by different palladium catalysts.
shown in Figure 9. Notably, there
was no induction period in these
reactions with or without the
poisoning agent.
Aryl halide
Catalyst
Yield [wt%]
Ref.
p-bromoacetophenone
p-bromoacetophenone
p-bromoanisole
p-bromotoluene
p-bromoanisole
oxime carbapalladacycle anchored to MCM-41
oxime carbapalladacycle anchored to silica
Pd-containing MOF
Pd catalyst supported on mesoporous molecular sieves
Pd nanoparticles embedded in porous (4 nm)
silica activated under H2
>99[a]
>99[b]
84[c]
quant.[d]
96[e]
[34]
[37]
[38]
[39]
[40]
Three-phase test[33,34]
To ascertain whether the reac-
tions were truly heterogeneous,
we performed the three-phase
test for the Suzuki reaction by
p-bromotoluene
bromobenzene
bromobenzene
phosphinoferrocenyl carboxamides–Pd complex
Pd-containing (0.1%!4.5%) basic zeolites
Pd-containing (1%) basic zeolite
100[f]
8!85[g]
10[h]
[41]
[42]
[42]
this study
p-bromoacetophenone
Sr-MOF-1-PI-Pd
100[i]
using
a designed aryl halide
[a] Water, 1008C, <0.1 h. [b] Water, 1008C, <0.1 h. [c] Ethanol, 258C, 48 h. [d] Ethanol, 758C, 24 h. [e] DMF,
1358C, 24 h. [f] Ethanol–water, 808C, 16 h; [g] Ethanol/ethanol–water, 508C, 24 h. [h] Toluene, 508C, 24 h.
[i] Ethanol–water, 808C, 1.5 h.
under standard conditions, as
described in the Experimental
Section (Scheme S1 in the
Supporting Information). The
compounds obtained through this process were p-phenylnitro-
benzene and p-bromoacetophenone. The expected Suzuki
product for p-bromoacetophenone, that is, p-phenylacetophe-
none was not detected. This clearly shows that p-bromoaceto-
phenone has not participated in the coupling reaction while
anchored on MCM-41. Should there be any leaching of palladi-
um species from Sr-MOF-1-PI-Pd, anchored p-bromoacetophe-
catalytic activity was observed in subsequent cycles.[40] Step-
ˇ
ˇ
ˇ
nicka et al. also reported the Suzuki coupling of p-bromo-
toluene in ethanol/water catalyzed by a palladium complex of
phosphinoferrocenyl carboxamides bearing glycine pendant
groups under homogeneous conditions with high yield and se-
lectivity.[41] Corma et al. observed palladium leaching in the
Suzuki coupling reaction catalyzed by palladium-containing
&
&
Chem. Eur. J. 2015, 21, 1 – 11
www.chemeurj.org
8
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
under an inert (nitrogen) atmosphere. After 15 days, the resulting
pale-yellow solid was collected by centrifugation, washed with dry
CH3CN, and dried in vacuum at 1208C. Elemental analysis was per-
formed on samples outgassed under vacuum (1208C, 12 h); ele-
mental analysis calcd (%) for Sr2(O)(ATA)0.48(PITA)0.52 (corresponding
to 52% amine functionalization): C 32.62, H 1.62, N 3.42; found: C
32.68, H 1.58, N 3.35.
basic zeolites in ethanol–water/ethanol medium and toluene
was used as a solvent to avoid metal leaching.[42] This is the
major drawback of a heterogeneous catalytic system, in com-
parison to homogeneous counterparts. The present catalyst,
Sr-MOF-1-PI-Pd, demonstrates a comparable efficiency in all of
the reactions in terms of yield, cost, reaction time, selectivity,
TOF, and reusability.
Synthesis of Sr-MOF-PI-Pd [Sr2(O)(ATA)1ꢀx(PITAꢀPdCl2)x]
Conclusion
Sr-MOF-PI-Pd was prepared by stirring desolvated Sr-MOF-1-PI (1 g)
with (0.053 g, [PdCl2] 0.3 mmol) in dry CH3CN (15 mL) for 12 h
under an inert (nitrogen) atmosphere. The brownish yellow solid
thus formed was then filtered, dried in vacuum at 1208C, and
washed with CH3CN by using Soxhlet extraction for 10 h to
remove any unanchored palladium species and dried again in
vacuum at 1208C. Elemental analysis was performed on samples
outgassed under vacuum (1208C, 12 h); elemental analysis calcd
(%) for Sr2(O)ATA)0.48(PITA-PdCl2)0.52 (corresponding to 52% amine
functionalization and quantitative palladium uptake): C 26.63, H
1.32, N 2.79; found: C 26.67, H 1.28, N 2.73. The amount of Pd in
the final solid was determined by atomic absorption spectrometry:
calcd: Pd 11.03%; found: Pd 11.11% (10.44ꢂ10ꢀ2 mol%).
We succeeded in designing a novel amino-functionalized MOF
based on strontium carboxylate. The compound underwent
SC-to-SC transformation by desolvation to form a highly
porous 3D MOF with pendant amines group for postfunction-
alization. By postmodification, a new heterogeneous catalyst
for carbon–carbon coupling reactions was developed by an-
choring a PdII Schiff base moiety into the microporous Sr-MOF-
1 catalyst. The catalyst showed a high activity towards the
Suzuki cross-coupling reaction in environmentally friendly sol-
vents (20% H2O/EtOH and EtOH) under mild reaction condi-
tions. The catalytic system tolerated a broad range of function-
al groups. The possibility of easy recycling of the catalyst and
mild reaction conditions make the catalyst cheap and highly
desirable to address environmental concerns. The gas adsorp-
tion capability also revealed promising results that could com-
pete with well-established prototype MOFs; thus, Sr-MOF-1 is
a novel addition to the MOF series based on alkaline-earth
metals that can be postmodified and used as a heterogeneous
catalyst.
Preparation of PBA-MCM-41
Anchoring of (3-aminopropyl)triethoxysilane (3-APTES) into MCM-
41 was achieved by stirring MCM-41 (0.1 g) with 3-APTES (0.18 g,
0.81 mmol) in dry chloroform at RT for 12 h under a nitrogen at-
mosphere. The white solid MCM-41-(SiCH2CH2CH2NH2)x thus
produced was filtered and washed with chloroform and dichloro-
methane. This solid was then heated at reflux with p-bromoaceto-
phenone (10 g, 50 mmol) in methanol (10 mL) for 3 h at 608C. The
resulting yellowish solid PBA-MCM-41 was then collected by
filtration and dried in a desiccator (Scheme 3).
Experimental Section
Synthesis of Sr-MOF-1’
Compound Sr-MOF-1’ was prepared through the following proce-
dure: Sr(NO3)2 (1.5 mmol, 316 mg) and 2-aminoterephthalic acid
(1 mmol, 210 mg) was mixed in DMF (10 mL) and stirred for 1 h to
form a light-yellow homogeneous solution, which was transferred
into a 25 mL Teflon-lined autoclave and kept in a preheated oven
at 1608C for 3 days. After slow cooling to room temperature over
a period of 6 h, block-shaped, light-yellow crystals were obtained
(72% yield based on metal ion). The crystals were kept in the
mother liquor. Elemental analysis calcd (%) for {Sr(ATA)(m-DMF)}: C
38.85, H 3.52, N 4.11; found: C 39.14, H 3.89, N 4.82.
Scheme 3. a) Organic modification of Si-MCM-41 with APTES/CHCl3 and
b) anchoring of p-bromoacetophenone onto MCM-41 (in ethanol).
SC-to-SC transformation to prepare Sr-MOF-1
The crystals formed initially were removed from the mother liquor
and washed with DMF and EtOH and dried under vacuum at 708C
for 24 h. DMF molecules were removed during this period and the
obtained desolvated crystals were kept for single-crystal X-ray anal-
ysis. Elemental analysis calcd (%) for {Sr2(ATA)(m-O)}: C 25.35, H 1.34,
N 3.79; found: C 24.64, H 1.76, N 3.98.
CCDC 991451 and 991452 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgements
Synthesis of Sr-MOF-PI [Sr2(O)(ATA)1ꢀx(PITA)x] (PITA=2-pyri-
dylimine terephthalate)
R.S. thanks the FCT for a post-doctoral grant (SFRH/BPD/
71798/2010). The Portuguese group is financially supported by
FEDER through the Programa Operacional Factores de Com-
petitividade—COMPETE and national funds through the FCT—
Pyridine-2-aldehyde (0.428 g, 4 mmol) was dissolved in dry CH3CN
(15 mL) before freshly prepared desolvated Sr-MOF-1 (1 g) was im-
mersed, and the reaction mixture was allowed to stand for 15 days
Chem. Eur. J. 2015, 21, 1 – 11
www.chemeurj.org
9
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
[17] V. A. Blatov, A. P. Shevchenko, D. M. Proserpio, Cryst. Growth Des. 2014,
14, 3576–3586.
[18] P. Pelagattia, M. Carcellia, M. Costab, S. Ianellia, C. Pelizzia, D. Rogolinoa,
J. Mol. Catal. A 2005, 226, 107–110.
Fundażo para a CiÞncia e Tecnologia within CICECO project
FCOMP-01-0124-FERDER-037271 (FCT Ref. Pest-C/CTM/LA0011/
2013).
[19] Y. Fan, W. You, W. Huang, J.-L. Liu, Y.-N. Wang, Polyhedron 2010, 29,
1149–1155.
Keywords: cross-coupling · heterogeneous catalysis · metal–
organic frameworks · strontium · structure elucidation
[20] S. Brunauer, P. H. Emmett, E. Teller, J. Am. Chem. Soc. 1938, 60, 309.
[21] a) D.-X. Xue, A. J. Cairns, Y. Belmabkhout, L. Wojtas, Y. Liu, M. H. Alkordi,
M. Eddaoudi, J. Am. Chem. Soc. 2013, 135, 7660–7667; b) K. Sumida,
D. L. Rogow, J. A. Mason, T. M. McDonald, E. D. Bloch, Z. R. Herm, T.-H.
Bae, J. R. Long, Chem. Rev. 2012, 112, 724–781.
[22] a) N. Planas, A. L. Dzubak, R. Poloni, L.-C. Lin, A. McManus, T. M. McDo-
nald, J. B. Neaton, J. R. Long, B. Smit, L. Gagliardi, J. Am. Chem. Soc.
2013, 135, 7402–7405; b) T. M. McDonald, W. R. Lee, J. A. Mason, B. M.
Wiers, C. S. Hong, J. R. Long, J. Am. Chem. Soc. 2012, 134, 7056–7065.
[23] a) J. An, S. J. Geib, N. L. Rosi, J. Am. Chem. Soc. 2010, 132, 38–39; b) R.
Vaidhyanathan, J. Liang, S. S. Iremonger, G. K. H. Shimizu, Supramol.
Chem. 2011, 23, 278–282; c) Y. E. Cheon, J. Park, M. P. Suh, Chem.
Commun. 2009, 5436–5438; d) R. Vaidhyanathan, S. S. Iremonger, K. W.
Dawson, G. K. H. Shimizu, Chem. Commun. 2009, 5230–5232; e) B.
Arstad, H. Fjellvꢇg, K. O. Kongshaug, O. Swang, R. Blom, Adsorption
2008, 14, 755–762; f) A. R. Millward, O. M. Yaghi, J. Am. Chem. Soc.
2005, 127, 17998.
[1] a) J.-R. Li, J. Sculley, H.-C. Zhou, Chem. Rev. 2012, 112, 869; b) S. Kitaga-
wa, K. Uemura, Chem. Soc. Rev. 2005, 34, 109; c) H.-C. Zhou, J.-R. Li,
O. M. Yaghi, Chem. Rev. 2012, 112, 673.
[2] a) A. Corma, H. Garcꢄa, F. X. L. i Xamena, Chem. Rev. 2010, 110, 4606;
b) J. Y. Lee, O. K. Farha, J. Roberts, K. A. Scheidt, S. B. T. Nguyen, J. T.
Hupp, Chem. Soc. Rev. 2009, 38, 1450; c) M. A. Gotthardt, A. Beilmann,
R. Schoch, J. Engelke, W. Kleist, RSC Adv. 2013, 3, 10676; d) M. A. Got-
thardt, R. Schoch, T. S. Brunner, M. Bauer, W. Kleist, ChemPlusChem
2015, 80, 188–195.
[3] a) M. Kurmoo, Chem. Soc. Rev. 2009, 38, 1353; b) Y.-F. Zeng, X. F.-C. Hu,
X.-H. Bu, Chem. Soc. Rev. 2009, 38, 469; c) R. Liu, L. Li, X. Wang, P. Yang,
C. Wang, D. Liao, J.-P. Sutter, Chem. Commun. 2010, 46, 2566; d) A. M.
Ako, V. Mereacre, R. Clꢅrac, W. Wernsdorfer, I. J. Hewitt, C. E. Anson, A. K.
Powell, Chem. Commun. 2009, 544; e) S. K. Langley, B. Moubaraki, K. S.
Murray, Dalton Trans. 2010, 39, 5066; f) H. Miyasaka, M. Julve, M. Yama-
shita, R. Clꢅrac, Inorg. Chem. 2009, 48, 3420.
[24] W. Lu, J. Sculley, D.-Q. Yuan, R. Krishna, H.-C. Zhou, J. Phys. Chem. C
2013, 117, 4057–4061.
[4] a) W. Morris, B. Leung, H. Furukawa, O. K. Yaghi, N. He, H. Hayashi, Y.
Houndonougbo, M. Asta, B. B. Laird, O. M. Yaghi, J. Am. Chem. Soc.
2010, 132, 11006; b) C. J. Doonan, W. Morris, H. Furukawa, O. M. Yaghi,
J. Am. Chem. Soc. 2009, 131, 9492; c) H. Sato, R. Matsuda, K. Sugimoto,
M. Takata, S. Kitagawa, Nat. Mater. 2010, 9, 661.
[5] a) O. M. Yaghi, M. O’Keeffe, N. W. Ockwig, H. K. Chae, M. Eddaoudi, J.
Kim, Nature 2003, 423, 705–714; b) H. Furukawa, K. E. Cordova, M.
O’Keeffe, O. M. Yaghi, Science 2013, 341, 974 and references therein.
[6] a) T. J. Colacot, Platinum Met. Rev. 2011, 55, 84–90 and references there-
in; b) L. Xue, Z. Lin, Chem. Soc. Rev. 2010, 39, 1692–1705; c) G. P.
McGlacken, I. J. S. Fairiamb, Eur. J. Org. Chem. 2009, 4011–4029; d) J.
Muzart, Tetrahedron 2005, 61, 4179–4212.
[25] J. L. C. Rowsell, O. M. Yaghi, J. Am. Chem. Soc. 2006, 128, 1304–1315.
[26] M. P. Suh, H. J. Park, T. K. Prasad, D.-W. Lim, Chem. Rev. 2012, 112, 782–
835.
[27] L. Schlapbach, A. Zuttel, Nature 2001, 414, 353–358.
[28] a) S. Y. Gao, Z. L. Zheng, J. Lꢆ, R. Cao, Chem. Commun. 2010, 46, 7584–
7586; b) M. Trilla, R. Pleixats, M. W. C. Man, C. Bied, J. J. E. Moreau, Adv.
Synth. Catal. 2008, 350, 577–590; c) M. Lombardo, M. Chiarucci, C.
Trombini, Green Chem. 2009, 11, 574–579; d) H. Hagiwara, K. H. Ko, T.
Hoshi, T. Suzuki, Chem. Commun. 2007, 2838–2840; e) Z. Guan, J. Hu, Y.
Gu, H. Zhang, G. Lia, T. Li, Green Chem. 2012, 14, 1964–1970; f) J. Z.
Zhang, W. Q. Zhang, Y. Wang, M. C. Zhang, Adv. Synth. Catal. 2008, 350,
2065–2076.
[7] a) N. Miyaura, A. Suzuki, Chem. Rev. 1995, 95, 2457–2483; b) A. Suzuki,
J. Organomet. Chem. 1999, 576, 147–168; c) J. K. Stille, Angew. Chem.
Int. Ed. Engl. 1986, 25, 508–524; Angew. Chem. 1986, 98, 504–519.
[8] B. M. Choudary, S. Madhi, N. S. Chowdari, M. L. Kantam, B. Sreedhar, J.
Am. Chem. Soc. 2002, 124, 14127–14136.
[9] a) D. Farrusseng, S. Aguado, C. Pinel, Angew. Chem. Int. Ed. 2009, 48,
7502–7513; Angew. Chem. 2009, 121, 7638–7649; b) C. Martꢄnez, A.
Corma, Coord. Chem. Rev. 2011, 255, 1558–1580; c) M. Ranocchiari, J. A.
van Bokhoven, Phys. Chem. Chem. Phys. 2011, 13, 6388–6396; d) V. Cal-
vino-Casilda, R. M. Martꢄn-Aranda, Recent Pat. Chem. Eng. 2011, 4, 1–16.
[10] a) W. Lu, Z. Wei, Z.-Y. Gu, T.-F. Liu, J. Park, J. Park, J. Tian, M. Zhang, Q.
Zhang, T. Gentle, M. Bosch, H.-C. Zhou, Chem. Soc. Rev. 2014, 43, 5561–
5593; b) W. Lu, D. Yuan, T. A. Makal, J.-R. Li, H.-C. Zhou, Angew. Chem.
Int. Ed. 2012, 51, 1580–1584; Angew. Chem. 2012, 124, 1612–1616.
[11] a) L. Yin, J. Liebscher, Chem. Rev. 2007, 107, 133–173; b) N. E. Leadbeat-
er, M. Marco, Chem. Rev. 2002, 102, 3217–3274.
[12] a) J. Juan-AlcaÇiz, J. Gascon, F. Kapteijn, J. Mater. Chem. 2012, 22,
10102–10118; b) J. S. Seo, D. Whang, H. Y. Lee, S. I. Jun, J. Oh, Y. J. Jeon,
K. Kim, Nature 2000, 404, 982–986; c) Z. Wang, S. M. Cohen, J. Am.
Chem. Soc. 2007, 129, 12368–12369.
[13] A. Dhakshinamoorthy, H. Garcia, Chem. Soc. Rev. 2012, 41, 5262–5284.
[14] J. Huang, W. Wang, H. Li, ACS Catal. 2013, 3, 1526–1536 and references
therein.
[29] D. Astruc, Inorg. Chem. 2007, 46, 1884–1894.
[30] a) K. Shimizu, T. Kan-no, T. Kodama, H. Hagiwara, Y. Kitayama, Tetrahe-
dron Lett. 2002, 43, 5653–5655; b) A. Primo, M. Liebel, F. Quignard,
Chem. Mater. 2009, 21, 621–627.
[31] a) V. Calꢈ, A. Nacci, A. Monopoli, F. Montingelli, J. Org. Chem. 2005, 70,
6040–6044; b) S. Bhunia, R. Sen, S. Koner, Inorg. Chim. Acta 2010, 363,
3993–3999.
[32] a) J. Zhou, X. Guo, C. Tu, X. Li, H. Sun, J. Organomet. Chem. 2009, 694,
697–702; b) M. Nonnenmacher, D. Kunz, F. Rominger, T. Oeser, J. Orga-
nomet. Chem. 2007, 692, 2554–2563; c) H. Yang, X. Han, Z. Ma, R.
Wang, J. Liu, X. Ji, Green Chem. 2010, 12, 441–451.
[33] A. Corma, D. Das, H. Garcꢄa, A. Leyva, J. Catal. 2005, 229, 322–331.
[34] C. Baleiz¼o, A. Corma, H. Garcꢄa, A. Leyva, J. Org. Chem. 2004, 69, 439–
446.
[35] J. M. Richardson, C. W. Jones, J. Catal. 2007, 251, 80–93.
[36] J. D. Webb, S. MacQuarrie, K. McEleney, C. M. Crudden, J. Catal. 2007,
252, 97–109.
[37] C. Baleiz¼o, A. Corma, H. Garcꢄa, A. Leyva, Chem. Commun. 2003, 606–
607.
[38] F. X. Llabrꢅs i Xamena, A. Abad, A. Corma, H. Garcꢄa, J. Catal. 2007, 250,
294–298.
ˇ
ˇ
ˇ
ˇ
ˇ
[39] J. Demel, M. Lamac, J. Cejka, P. Stepnicka, ChemSusChem 2009, 2, 442–
451.
[15] a) R. Sen, S. Bhunia, D. Mal, S. Koner, Y. Miyashita, K.-I. Okamoto, Lang-
muir 2009, 25, 13667–13672; b) R. Sen, R. Bera, A. Bhattacharjee, P. Gꢆt-
lich, S. Ghosh, A. K. Mukherjee, S. Koner, Langmuir 2008, 24, 5970–
5975; c) R. Sen, S. Koner, D. K. Hazra, M. Helliwell, M. Mukherjee, Eur. J.
Inorg. Chem. 2011, 241–248; d) R. Sen, D. K. Hazra, M. Mukherjee, S.
Koner, Eur. J. Inorg. Chem. 2011, 2826–2831.
[40] G. Budroni, A. Corma, H. Garcꢄa, A. Primo, J. Catal. 2007, 251, 345–353.
ˇ
ˇ
ˇ
ˇ
[41] J. Tauchman, I. Cꢄsarovꢉ, P. Stepnicka, Organometallics 2009, 28, 3288–
3320.
[42] A. Corma, H. Garcꢄa, A. Leyva, Appl. Catal. A 2002, 236, 179–185.
[16] a) R. Sen, D. Saha, S. Koner, Chem. Eur. J. 2012, 18, 5979–5986; b) D.
Saha, R. Sen, T. Maity, S. Koner, Dalton Trans. 2012, 41, 7399–7408.
Received: October 16, 2014
Published online on && &&, 0000
&
&
Chem. Eur. J. 2015, 21, 1 – 11
www.chemeurj.org
10
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
FULL PAPER
Expanding on the bare essentials: A
novel amino-functionalized strontium
metal–organic framework (Sr-MOF) has
been synthesized that undergoes
single-crystal to single-crystal transfor-
mation to become a microporous MOF
(see figure). Palladium(II) has been anch-
ored onto the arm of the framework
and the obtained compound has been
used in the Suzuki cross-coupling
reaction. The high efficiency of the
catalyst remains unaltered after five
successive cycles.
&
Heterogeneous Catalysis
R. Sen,* D. Saha, S. Koner, P. Brand¼o,
Z. Lin*
&& – &&
Single Crystal to Single Crystal (SC-to-
SC) Transformation from a Nonporous
to Porous Metal–Organic Framework
and Its Application Potential in Gas
Adsorption and Suzuki Coupling
Reaction through Postmodification
Chem. Eur. J. 2015, 21, 1 – 11
www.chemeurj.org
11
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ