A HKUST-1 MOF inclusion compound with in-situ reduced copper(I) as [Cu(NCCH3)4]+cation complex in the octahedral A-type pore

Article abstract of DOI:10.1016/j.poly.2016.06.039

Hydrothermal reaction of racemic 1,2-bis(1,2,4-triazol-4-yl)propane (rac-btrip) and benzene-1,3,5-tricarboxylic acid (H₃btc) with copper(II) acetate in an aqueous triethylamine and acetonitrile mixture afforded blue-green cuboctahedral crystals

Full text of DOI:10.1016/j.poly.2016.06.039

Accepted Manuscript
A HKUST-1 MOF inclusion compound with in-situ reduced copper(I) as
+
[
Cu(NCCH ) ] cation complex in the octahedral A-type pore
3
4
Anas Tahli, Reda F.M. Elshaarawy, Ümit Köc, Anna Christin Kautz, Christoph
Janiak
PII:
S0277-5387(16)30273-X
http://dx.doi.org/10.1016/j.poly.2016.06.039
POLY 12080
DOI:
Reference:
To appear in:
Polyhedron
Received Date:
Accepted Date:
17 February 2016
22 June 2016
Please cite this article as: A. Tahli, R.F.M. Elshaarawy, U. Köc, A.C. Kautz, C. Janiak, A HKUST-1 MOF inclusion
+
compound with in-situ reduced copper(I) as [Cu(NCCH ) ] cation complex in the octahedral A-type pore,
3
4
Polyhedron (2016), doi: http://dx.doi.org/10.1016/j.poly.2016.06.039
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+
A HKUST-1 MOF inclusion compound with in-situ reduced copper(I) as [Cu(NCCH
cation complex in the octahedral A-type pore
3
4
) ]
a,b
a,c
a
a
Anas Tahli, Reda F. M. Elshaarawy, Ümit Köc, Anna Christin Kautz, Christoph
a,
Janiak 
a
Institut für Anorganische Chemie und Strukturchemie, Heinrich-Heine Universität
Düsseldorf, Universitätsstr. 1, D-40225 Düsseldorf, Germany. Email: janiak@hhu.de
b
Faculty of Science, Al-Furat University, Deir Ezzor, Syria
c
Faculty of Science, Suez University, Suez, Egypt
1

Graphical Abstract for
+
A HKUST-1 MOF inclusion compound with in-situ reduced copper(I) as [Cu(NCCH
complex in the octahedral A-type pore
3
)
4
] cation
The first HKUST-1 inclusion derivative with a defined guest in the octahedral A-type pores.
2

Abstract
Hydrothermal reaction of racemic 1,2-bis(1,2,4-triazol-4-yl)propane (rac-btrip) and benzene-
1
,3,5-tricarboxylic acid (H
acetonitrile mixture afforded blue-green cuboctahedral crystals of the MOF inclusion
compound 3D-Cu(NCCH Cu ( -btc) (O CCH ) (H O,CH CN) , 1. This
MOF is isostructural with the prototypical MOF HKUST-1 (Cu (btc) , Cu-btc) and the first
3
btc) with copper(II) acetate in an aqueous triethylamine and
3
)
4
3
6
2

2
2
3
2
3
x
(btrip)1.5
}
n
3
2
HKUST-1 derivative which accommodates a defined guest, namely the cationic
+
tetra(acetonitrile)copper(I) complex [Cu(NCCH
3
)
4
] in the A-type octahedral pores of the 3D
HKUST-1 framework. In-situ reduction of Cu(II) to Cu(I) in the course of the hydrothermal
synthesis is afforded by the sacrificial btrip ligand which is not incorporated as a linker but as
1
a template molecule into the cuboctahedral B- and C-type pores according to H NMR
digestion analysis. N
2
adsorption isotherm for activated HKUST-1 inclusion compound 1
2
gave a BET surface area of 576 m /g.
Keywords: Metal-organic framework, MOF; HKUST-1; inclusion compound; in-situ
reduction; mixed-valence
1
Introduction
Porous coordination polymers (PCPs) also called metal-organic frameworks (MOFs) are
intensively investigated due to their potential applications, such as gas storage [1], separation
processes [2], catalysis [3], conductivity [4] and reversible water sorption for heat
transformation [5]. Reaction conditions such as solvents, temperature, pH, the type of
bridging ligands, the counter anions of metal salts can influence the still difficult to predict
resulting structure of PCPs. Coordination polymers based on mixed-linkers [6] may allow for
a fine-tuning of MOF properties and can show additional characteristics such as crystal-to-
crystal transformations [7], short and long-range magnetic ordering [8], luminescence [9]
etc.[10].
The combination of neutral nitrogen donor ligands with anionic carboxylate ligands are
frequent choices for the synthesis of mixed-ligand networks [10]. The linker properties of 1,2-
bis(1,2,4-triazol-4-yl)ethane (abbreviated as btre, Scheme 1) have recently been intensely
studied in mixed-linker MOFs [7-11,12] and single-linker networks [13]. Herein, we report an
attempt to construct mixed-linker networks by use of a chiral variant of btre, namely racemic
1
,2-bis(1,2,4-triazol-4-yl)propane, rac-btrip (Scheme 1) in combination with benzene-1,3,5-
3
–
tricarboxylate, btc . The hydrothermal reaction yielded, however, an inclusion compound of
3

the well-know, prototypical MOF HKUST-1 (Cu
3
(btc) , Cu-btc) [14] which is one of the most
2
studied MOFs, because of easy formation [15], high porosity and known properties associated
with this compound [16]. Here, we obtained HKUST-1 with the molecular cationic complex
+
[
Cu(NCCH
3
)
4
] as guest in the pores.
Scheme 1. 1,2-Bis(1,2,4-triazol-4-yl)alkane linkers.
2
2
Experimental section
.1 Materials and instruments
Reagents and solvents were obtained from commercial sources and used without further
purification. A programmable oven type UFP 400 from Memmert GmbH was used for solvo-
®
/
hydrothermal synthesis. The reactions were carried out in DURAN culture glass tubes with
PTFE-faced sealing wad, diameter 12 mm, height 100 mm and DIN thread 14 GL, which
were closed with red PBT screw cap (Fig. S1, Supp. Info.), suitable for hydro-/solvothermal
synthesis for coordination polymer synthesis up to 150 °C instead of an autoclave. The
contents only come into contact with the glass and PTFE seal. The light microscopy images
were observed with a Leica MS5 binocular eyepiece with transmitted light and polarization
filter. The images of isolated crystals were taken with a Nikon COOLPIX 4500 digital camera
through a special ocular connection. Infrared spectra were recorded with a Bruker Optik
TENSOR 37 spectrophotometer using a Diamond ATR (Attenuated Total Reflection) unit
–
1
from 4000 to 500 cm . The following abbreviations were used to classify spectral bands: br
(
broad), sh (shoulder), very weak (vw), w (weak), m (medium), s (strong) and vs (very
1
strong). The H NMR spectra were recorded either on a Bruker Advance DRX 300 MHz
NMR spectrometer with calibration against the residual protonated solvent signal D O (4.79
2
ppm). Thermogravimetric analysis was carried out in a simultaneous thermoanalysis
apparatus TG 209 F3 from NETZSCH GmbH under flowing nitrogen gas 30 mL/min with a
–
1
heating rate 10 °C min in the temperature range from 30 °C to 600 °C using Al crucible.
Powder X-ray diffraction patterns were measured at ambient temperature using a Bruker D2
PHASER in the Bragg-Brentano configuration with Cu-Kα radiation (λ = 1.54184 Å), nickel
filter and stationary flat panel sample holder in the range 2θ = 5–50° (step size 0.02° in 2θ).
Simulated powder patterns were based on single-crystal data and calculated using the STOE
4

XPOW
Win
software package [17] or Mercury v. 3.3 software [18]. The as-synthesized samples
were dried in vacuum for ca. 2 hours at 40 °C before PXRD measurement.
Nitrogen sorption measurement was carried out with a Quantachrome Autosorb NOVA 4000e
automated gas sorption system. Before the gas adsorption, the sample was washed in water
twice over night, dried and loaded into glass tubes capped with septa. The weighed tubes were
attached to the corresponding degassing port of the sorption analyzer, degassed under vacuum
for 3 h at 200 °C, weighed again and then transferred to the analysis port of the sorption
analyzer. BET surface areas were calculated from the nitrogen physisorption isotherms. The
DFT calculations for the pore size distribution curves were made using the Nova Win 11.03
software employing the "N at 77 K, slit pore, NL-DFT equilibrium" model [19]. Theoretical
2
porosity calculations for the potential solvent volume in the solvent-depleted single-crystal X-
ray structures are carried out with PLATON calc void/solv [20].
2
.2 Synthesis of 1,2-bis(1,2,4-triazol-4-yl)propane, rac-btrip
Racemic 1,2-bis(1,2,4-triazol-4-yl)propane (rac-btrip) was synthesized by the reaction of rac-
,2-diaminopropane with N,N'-dimethylformamide azine using p-toluene sulfonic acid
monohydrate as a catalyst in toluene under extra dry conditions at 120-130 °C [21,22,23].
N,N'-Dimethylformamide azine was synthesized from thionyl chloride, SOCl , N,N`-
O following a literature
1
2
dimethylformamide, DMF, and hydrazine monohydrate, N
procedure [21].
2
H ·H
4 2
2
.3 Synthesis of 3D-Cu(NCCH
O,CH CN) , 1
A solution of 16 mg (0.080 mmol) of copper acetate, Cu(OAc)
and 0.5 mL of water and a solution of 14 mg (0.080 mmol) of rac-btrip in 0.5 mL water were
mixed in a glass tube for about 3-5 minutes. A portion of 8.4 mg (0.040 mmol) of H btc in
.75 mL of Et N/H O solution (0.16 mol/L, 3eq to H btc) was dissolved using an ultrasonic
bath and heating at 45-50 °C. As H btc was deprotonated by the basic amine medium it
dissolved. Without the presence of base, H btc did not dissolve under the above temperature
3
)
4
Cu
3
(
6
-btc)
2

2
(O
2
CCH
3
)
(
H
2
3
x
(btrip)1.5
}
n
2
·H O in 0.5 mL of acetonitrile
2
3
0
3
2
3
3
3
conditions in water. The resulting solution was combined with the previous mixture and
shaken again for ca. 5 minutes in a DURAN glass tube, which was pressure sealed and then
placed in a programmable furnace. The sample was heated to 125°C during 3 h, held at that
temperature for 48 h, then cooled at a rate 5 or 10°C/h to ambient temperature. The resulting
5

blue-green single crystals of cuboctahedral shape (Fig. 1, Fig. S2 in Supp. Info.) were
separated from some amorphous precipitate by decantation and washed with water. The
reaction was repeated several times and found to be reproducible. The crystals are insoluble in
water, ethanol or methanol. Yield 16 mg, 0.01 mmol, 90 % based on Cu(OAc)
2
, quantitative
–
1
based on H
3
btc. FT-IR (ATR, cm ): 3109 (w, ν, C-H), 1646 (s, νasym C=O), 1612 (w, νsym
C=O), 1240 (s, νasym C-O), 1190 (s, νsym C-O), 871 (w,  C-H), 758, 726 (s,  , 1,3,5-
trisubstituted benzene ring of btc). Copper acetate could also be replaced by 18 mg (0.080
mmol) of Cu(NO
3
)
2
·2.5H O to yield crystals which gave an identical powder X-ray
2
diffraction pattern after activation (Fig. S3a in Supp. Info). The phase purity and
representative nature of the single crystals for 1 were confirmed by the comparison of the
measured and simulated PXRD patterns (Fig. S3b in Supp. Info). Some deviations between
the simulated and measured PXRD are, however, expected as the simulated diffractogram
cannot account for the electron density contributions in the pores which was squeezed out by
PLATON (see below).
Fig. 1. Cuboctahedal single crystals of 1 (see Fig. S2 in Supp. Info for further photographs).
2
.4 Crystallographic data collection and refinement.
Suitable single crystals (Fig. 1 and S2, Supp. Info) were carefully selected under a polarizing
microscope and mounted in oil in a glass loop. Data collection: Bruker AXS Kappa APEX II
CCD area-detector diffractometer with multilayer-mirror monochromator, Mo-Kα radiation (λ
=
0.71073 Å) from microfocus source, double-pass method with - and ω-scans. Data
collection with APEX II [24], cell refinement and data reduction with SAINT [25], empirical
absorption correction with SADABS [26]. Structure analysis and refinement: The structure
was solved by direct methods, SHELXS-97, refinement was carried out by full-matrix least
2
squares on F using the SHELXL-97 software suite [27]. All non-hydrogen positions were
6

found and refined with anisotropic temperature factors. Hydrogen atoms on the aromatic rings
and the carbon atoms were placed geometrically at calculated positions with an appropriate
riding model (AFIX 43 for aromatic CH and AFIX 137 for CH
3
) and an isotropic temperature
factor of Uiso(H) = 1.2 Ueq(CH) and 1.5 Ueq(CH ). The unit cell contains solvent or other guest
3
molecules, which have been treated as a diffuse contribution to the overall scattering without
specific atom positions by SQUEEZE/PLATON [20]. A total of 1131 electrons were
3
recovered in the unit cell void volume of 8925 Å which corresponds to ~141 electrons per
C
46.76
H24Cu
7
N
4
O
30 formula unit (Z = 8). The axial ligand on the Cu1 atom of the {Cu } node
2
is either an aqua ligand, an acetonitrile ligand or a partially occupied acetate ligand. For the
+
one [Cu(NCCH
3
)
4
] guest per neutral Cu
6
(btc) equivalent one anionic charge is needed. This
4
anion can be an acetate ligand which is then distributed over the six Cu1 atoms in the formula
unit. The occupancy of the C6 atom of the assumed carboxylate group was refined to 0.11503
which is higher than required for a 1/6 occupancy on each Cu1 atom with its occupation
factor of 0.25 due to the special position (0.25 : 6 = 0.04167). Hence, this C6 atom can also be
part of an acetonitrile group, which then would require the O2 atom to be a nitrogen atom (cf.
Fig. 2). The CH group and the second O atom of the acetate group were too diffuse to be
3
satisfactorily localized. Hence, their electron densities have been treated as a diffuse
contribution to the overall scattering without specific atom positions by SQUEEZE/PLATON.
Graphics were drawn with DIAMOND (Version 3.2) [28]. Details of the X-ray crystal data
structure determination are provided in the Table 1. The structural data has been deposited
with the Cambridge Crystallographic Data Center (No. 1451953).
Table 1. Crystal data and structure refinement for 1.
Empirical formula
Formula weight
Temperature
C
46.76
H
24Cu
7
N
4
O
30
1566.48
296(2) K
0.71073 Å
Cubic
Wavelength
Crystal system
Space group
F m -3 m
Unit cell dimensions
Volume
a = 26.446(3) Å
3
18496(4) Å
Z
8
–
3
Density (calculated)
Absorption coefficient µ
1.125 g/m
–
1
1.638 mm
7

F(000)
6204
3
Crystal size
0.10 x 0.10 x 0.10 mm
2.55 to 23.89°.

range for data collection
h, k, l Index ranges
–29,30, –30,30, –28,30
24718
Reflections collected
Independent reflections
Completeness to  = 23.89°
Max. and min. transmission
Data / restraints / parameters
Final R indices [I>2sigma(I)]
780 [R(int) = 0.0648]
99.4%
0.8534 and 0.8534
780 / 0 / 51
a
R1 = 0.0333, wR2 = 0.1048
R1 = 0.0353, wR2 = 0.1059
1.473
a
R indices (all data)
2
b
Goodness-of-fit on F
–
3
Largest diff. peak and hole
0.255 and –0.771 e Å
a
2
2 2
2 2 1/2
b
R
1
= [(║F
o
│–│F
c
║)/│F
o
│]; wR
2
= [ [w(F
o
–F
c
) ]/[w(F ) ]] . – Goodness-of-fit =
o
2
2 2
1/2
[
 [w(F
o
–F ) ] /(n–p)] .
c
3
Results and discussion
Blue-green crystals of 1 (Fig. 1 and Fig. S1, Supp. Info) were obtained from the hydrothermal
reaction of copper(II) acetate monohydrate in the presence of rac-btrip and H btc/Et N in a
water-acetonitrile solvent. Coordination frameworks constructed by metal ions and benzene-
tricarboxylic acid, H btc are extremely dependent on the deprotonation degree of H btc [29].
From the acid constants of H btc (pKa =2.12, pKa = 3.89, pKa = 5.20) [30], the
deprotonation H btc can be achieved by triethylamine, Et N as base. From single-crystal X-
3
3
3
3
3
1
2
3
3
3
ray diffraction analysis the composition of 1 is determined as the 3D-network of HKUST-1,
+
namely [Cu
2
(btc)
3
] with Cu(NCCH
3
)
4
 cations as guests in the octahedral (A-type) voids to
yield a solvent-guest-squeezed formula of 3D-Cu(NCCH
named tetra(acetonitrile)copper(I)-catena{acetatobis(benzenetricaboxylato)tricuprate(II)}
Fig. 2). It is known that Cu ions can be reduced in-situ to Cu by N-, O-, S-containing
3
)
4
Cu
3
(
6
-btc)
2

2
(O
2
CCH
3
n
)} ,
2
+
+
(
ligands,
such as
btre
[13],
4,4´-bipyridine,
pyridine-4-thiol,
quinoxaline,
nder
pyridinedicarboxylate and others under hydrothermal conditions [
hydro(solvo)thermal conditions
organo-nitrogen species behave not
8

only as ligands but also as reducing agents towards Cu(II). This reduction then results in a
decomposition of part of the organo-nitrogen species [13,34,35,36].
(
a)
(b)
(
c)
+
Fig. 2. (a) Representation of the Cu
2
paddlewheel unit with the guest complex Cu(NCCH
3
4
) 
(
50% thermal ellipsoid, H atoms at arbitrary radii). The axial ligand on the Cu1 is either an
aqua ligand, an acetonitrile ligand or a partially occupied acetate ligand (for charge balance).
Hence, the C6 atom can also be part of an acetontrile group which then would require the O2
+
atom to be a nitrogen atom. (b) Cu(NCCH
3
)
4
 cation in space-filling mode in the octahedral
+
pore A. (c) unit cell packing diagram with the Cu(NCCH
3
)
4
 cations in space-filling mode in
the octahedral pores A. Eight octahedral pores surround a cuboctahedral pore. In (b) and (c)
9

the ambiguous axial ligands on Cu1 have been omitted for clarity; in (c) hydrogen atoms were
also omitted. Selected distances and angles are given in Table 2.
Compound 1 crystallizes in the cubic crystal system with the centrosymmetric space group F
m-3m and eight formula units per unit cell. The asymmetric unit consists of a copper atom
(
Cu1, occupation factor 0.25) coordinated by a third of a btc ligand and an axial ligand plus a
second copper atom (Cu2, occupation factor 0.04167) with one acetonitrile ligand (Fig. 2a).
The Cu-btc framework in compound 1 is isostructural with the compound 3D-[Cu (
btc) (H O) , better known as HKUST-1 or Cu-btc reported by Williams et al. [14].
3
6
-
2
2
]
3 n
Therefore, we refrain here from a detailed description of the Cu-btc network.
Table 2. Selected distances (Å) and angles (°) in 1.
ii
Cu1-O1
Cu1-O2
Cu1···Cu1
O1-C1
C1-C2
1.9685(16)
2.142(5)
O1-Cu1-O1
O1-Cu1-O1
O1-Cu1-O1
O1-Cu1-O2
88.51(11)
167.35(10)
90.10(11)
96.33(5)
83.67(5)
180.00(13)
123.51(18)
109.5
iii
iv
i
2.6733(10)
1.260(2)
i
i
1.502(4)
O1-Cu1-Cu1
O2-Cu1-Cu1
C1-O1-Cu1
C2-C3
1.390(2)
Cu2-N
N-C4
2.009(11)
1.096(13)
1.442(16)
i
N-Cu2-N
C4-C5
C4-N-Cu2
N-C4-C5
180(1)
180(2)
Symmetry transformations: i = 0.5–x, y, 0.5–z; ii = z, y, x; iii = z, –y, x; iv = x, –y, z.
The tritopic btc linker, positioned on the crystallographic C
its three carboxylate groups. Each Cu paddlewheel unit (Fig. 2a) connects with four different
btc ligands, that leads to the formation an open extended porous 3D-framework (Fig. 2c). The
centers of six Cu -handles form the vertices of a super-octahedron (pore A) with four of the
3
axes, coordinates six Cu atoms at
2
2
eight triangular faces covered by four btc ligands. This octahedral pore A accommodates the
+
molecular complex cation Cu(CH
3
CN)
4

(Fig. 2b). The acetonitrile ligands from
+

Cu(CH
3
CN)
4
 point through the remaining four uncovered super-octahedral faces. The
distances between the Cu
2
centroids along the octahedral vertex is 9.35 Å and opposite Cu
2
centroids around octahedral pore are 13.22 Å apart. For charge-neutrality to the
+

Cu(CH
3
CN)
4
 cation an anion is needed. Most likely this comes from an axial acetato ligand
1
0

coordinated to one of the Cu
atoms of the {Cu } node are either an aqua ligand, an acetonitrile ligand or a partially
occupied acetate ligand. From this inherent disorder, only the directly bound atom to Cu could
be found and refined. Thus, the 3D network is of composition 3D-Cu(NCCH Cu (
btc) (O CCH ) (H O,CH CN) , tetra(acetonitrile)copper(I)-catena{acetatobis(benzene-
tricaboxylato)tricuprate(II)} hydrate or acetonitrile solvate.
In the FT-IR spectrum (ATR) of compound 1 (Figure S4, Supp. Info.) the absence of the
characteristic band of protonated carboxyl group (COOH) of H btc proves, that the
2
atoms of the paddlewheel SBU. The axial ligands on the Cu1
2
3
)
4
3
6
-
2

2
2
3
2
3
}
x n
3
–
1
carboxylate groups are completely deprotonated [37]. A band at 642 cm is attributed to the
triazole ring of the rac-btrip ligand in the cuboctahedral pores.
1
The H NMR spectrum of compound 1 (obtained by complete dissolution of 1 in NaOD/D
2
O)
shows the signals for both the btc and the rac-btrip ligands in a 2.7 : 1 ratio (based on the
three aryl protons and the methyl group of rac-btrip with also 3 H atoms) (Fig. S5a in Supp.
Info). The framework should not and does not have to stay intact for the NMR solution study.
The role of the NMR spectrum was solely to derive at the btc to btrip ligand ratio. In order to
bring the framework into solution it has to be broken apart ("digestive dissolution"). Thus, the
1
H NMR analysis of 1 suggests that the rac-btrip molecules are located in the channels of the
framework as non-coordinated guest molecules. Their high disorder made these rac-btrip
molecules unobservable by X-ray single-crystal structure analysis.
The option "'SQUEEZE" in PLATON [20] was used to remove diffuse contributions to the
overall scattering without specific atom positions and gave about 141 electrons per

Cu(NCCH
3
)
4
Cu
3
(
6
-btc)
2

2
} formula unit. A btrip molecule of formula C
7
H
10
6
N (178.20
g/mol) has 94 electrons, so that about 1.5 btrip ligands fit to 141 electrons. A ratio of 4 btc
ligands to 1.5 btrip ligands would match with the NMR ratio of 2.7 : 1. Hence, a more
complete
btc) (O
formula of
CCH )·(H O,CH
1
would correspond to
3D-Cu(CH
3
CN)
4
Cu
3
( -
6
2

2
2
3
2
3
CN)
x
(btrip)1.5} .
n
Isomorphous compounds of HKUST-1 with paddle-wheel SBUs and triangular btc ligands
have been reported with copper, iron, molybdenum, chromium, nickel and zinc [38]. HKUST-
1
structures have been reported with guest molecules or ions in the cuboctahedral pores B or
C (Fig. S6 in Supp. Info.). These HKUST-1 derivatives were synthesized with different
2
–
2–
2–
Keggin polyoxometalates (POMs) such as [HPW12
O
40] , [H
2
SiW12
O
40] , [H
2
GeW12
O
40] ,
2
–
2–
2–
4–
[
[
(
H
2
SiMo12
O
–
40] , [HPMo12
O
4–
40
]
and [HAsMo12
O
4–
40
]
[39], or such as [SiMo12
O
40] ,
3
5–
6–
PW12
O
40] , [PMo
6
W
6
O
40
]
[40], [PMo11VO40
]
[PMo10
V
2
O
40
]
and [PMo
9
V
3
O ]
40
Figures S7-S11, Supp. Info.) [41]. The HKUST-1 frameworks can encapsulate
1
1

metalloporphyrins
in
pores
B,
including
Fe(III)
or
Mn(III)
tetrakis(4-
sulphonatophenyl)porphyrin and Zn(II) tetrakis(4-methylpyridyl)porphyrin such that the
porphyrin encapsulated HKUST-1 materials demonstrate crystallographically resolved
porphyrin macrocycles in cavities reminiscent of heme pockets, while the remaining cavities
allow small molecules to reach the active site for catalysis, much like channels in heme
proteins (Figure S12, Supp. Info.) [42]. Metal complexes of meso-tetra(N-methyl-4-
2
+
pyridyl)porphine (TMPyP ) cation such as [Fe(III)TMPyP]Cl
5
, [Co(II)TMPyP]Cl
, [M(II)TMPyP] (M = Ni, Mg, Zn) can be encapsulated in pores B
Figure S13, Supp. Info.) [43]. Hence, to the best of our knowledge compound 1 appears to be
4
,
4
+
[
(
Mn(III)TMPyP]Cl
5
the first HKUST-1 derivative which occupies a defined guest species in its small octahedral
A-type pores.
3
.1 Thermal analysis
Thermogravimetric analysis (TGA) was carried out in the temperature range 30-600°C
following a pre-drying procedure of 2 h at 40 °C in vacuum of the sample during which the
+
CH
3
CN ligands of the Cu(NCCH
3
)
4
 cation were most likely lost already. Up to 200 °C a
mass loss of 20.6% is observed for 1. The loss of 1.5 eq. of btrip would account for a 17%
weight loss. In addition some axial aqua ligands on Cu1 may be lost as well. The de-solvated
and guest-depleted 3D-network is thermally stable up to 280 °C when the 3D-network
begins to decompose in one weight-loss step on further heating (obs. 44.05%). The final
residual mass of black precipitate is mostly assigned to CuO (obs. 34.84%) (Figure S14,
Supp. Info.).
3
.2
The potential permanent porosity was studied by nitrogen gas sorption measurements. The
porosity and BET surface area was evaluated from a N adsorption isotherm at 77 K. For
activation the sample was heated at 200 °C under vacuum for 3 h. The N isotherm in Figure
can largely be classified as a composite of Type I and II with an H4 hysteresis loop. The
N
2
sorption study
2
2
3
more pronounces uptake at low P/P is associated with the filling of micropores. The Type II
0
part at high P/P is given by the physisorption on non- to macroporous adsorbents. H4 loops
0
are often found with aggregated crystals of microporous zeolites, mesoporous zeolites and
micro-mesoporous carbons [44]. The Brunauer–Emmett–Teller (BET) surface area for 1 is
2
2
calculated as 576 m /g [45] (Langmuir surface area 676 m /g), its total pore volume V = 0.34
P
3
2
cm /g at P/P
0
= 0.95. The surface areas for HKUST-1, synthesized in DMF is 1507 m /g, V =
P
1
2

3
0
.75 cm /g [46]. The derived pore widths for 1 are distributed around 18 and from 27-38 Å
and beyond (pores of widths between 2 nm and 50 nm are mesopores). We ascribe the smaller
surface area and pore volume of 1 to the filling of the A-type pores with the Cu(I) cation. The
btrip ligand in the cuboctahedral B- and C-type pores is probably lost upon activation at 200
°C (as also suggested by TGA, see above) due to decomposition. This triazole ring
decomposition is likely accompanied by gas evolution which ruptures parts of the Cu-btc
frameworks leading to cracks and meso- to macroporous voids. At the same time
experimental PXRD patterns measured before and after N adsorption show that crystallinity
2
is retained upon activation (Figure S2, Supp. Info.). Hence, we suggest that the larger crystals
are shattered into smaller aggregated crystallites upon activation. This would be in line with
the H4 hysteresis loop which has been found, e.g., for aggregated crystals or microporous
zeolites [44].
Fig. 3. Nitrogen adsorption-desorption isotherms (left) at 77 K of 1, and the derived pore-size
distribution (right).
4
Conclusion
When H btc and rac-btrip were tried to combine with copper(II) salts in the presence of
triethylamine as deprotonating base under hydrothermal conditions, the successfully
crystallized product 1 had only the btc linker in the 3D network of {Cu(NCCH Cu (
btc) (O CCH )} . The network part of {Cu ( -btc) is isostructural with the
prototypical microporous MOF HKUST-1 3D-[Cu ( -btc) (H , also named Cu-btc. The
 is the first defined guest which occupies the A-type
3
3
)
4
3
6
-
2

2
2
3
n
3
6
2

2 n
}
3
6
2
2
O)
]
3 n
+
molecular complex cation Cu(NCCH
)
3 4
octahedral cages of the HKUST-1 network. The commonly occupied cuboctahedral B- and C-
1
type pores contain the btrip ligand which was found by H NMR after dissolution of the
washed crystalline product in a 2.7 : 1 (= 4 : 1.5) btc : btrip molar ratio. Together with some
1
3

additional water and acetonitrile solvent molecules the overall formula for 1 would then come
out to 3D-Cu(NCCH Cu ( -btc) (O CCH ) (H O,CH CN)
3
)
4
3
6
2

2
2
3
2
3
x
(btrip)1.5} .
n
5
Appendix A. Supplementary data
CCDC 1451953 contains the supplementary crystallographic data for compound 1. These data
can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from
the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(
+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
6
Acknowledgement
AT sincerely thanks the Al-Furat University and the Ministry of Higher Education in Syria for
the financial support (scholarship) during his study in Germany (language course, Master and
PhD degree). This work was funded by BMBF project OptiMat 03SF0492C.
7
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