Metal-organic framework based on copper(I) sulfate and 4,4′- bipyridine catalyzes the cyclopropanation of styrene

Article abstract of DOI:10.1016/j.jssc.2011.06.023

The hydrothermal synthesis of a new metal-organic framework (MOF) formulated as Cu₂(4,4′-bpy)₂SO₄· 6(H₂O), [abbreviation: (1); bpy or 4,4′-bpy=4,4′- bipyridine; SO₄^2-=sulfate group] has been reported. The structure of this MOF consists of Cu⁺ nodes connected via 4,4′-bpy to form infinite chains, with two neighboring chains further bridged on the nodes by SO₄^2-, resulting in a 1-D double chain network. Guest water molecules reside in between the chains and are hydrogen-bonded to the O and S atoms from the nearest sulfate groups, leading to the formation of a 3-D supramolecular framework. This MOF is good heterogeneous catalyst for the cyclopropanation of styrene, with high trans cyclopropane diastereoselectivity and was recycled and reused for three consecutive cycles without a significant loss of catalytic activity.

Full text of DOI:10.1016/j.jssc.2011.06.023

Journal of Solid State Chemistry 184 (2011) 2196–2203
Contents lists available at ScienceDirect
Journal of Solid State Chemistry
journal homepage: www.elsevier.com/locate/jssc
Metal-organic framework based on copper(I) sulfate and 4,40-bipyridine
catalyzes the cyclopropanation of styrene
n
n
~
Fa-Nian Shi , Ana Rosa Silva , Joao Rocha
Department of Chemistry, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal
a r t i c l e i n f o
a b s t r a c t
The hydrothermal synthesis of a new metal-organic framework (MOF) formulated as Cu2(4,40-
bpy)2SO4 ꢀ 6(H2O), [abbreviation: (1); bpy or 4,40-bpy¼4,40-bipyridine; SO24ꢁ ¼sulfate group] has been
reported. The structure of this MOF consists of Cuþ nodes connected via 4,40-bpy to form infinite
chains, with two neighboring chains further bridged on the nodes by SO24ꢁ, resulting in a 1-D double
chain network. Guest water molecules reside in between the chains and are hydrogen-bonded to the O
and S atoms from the nearest sulfate groups, leading to the formation of a 3-D supramolecular
framework. This MOF is good heterogeneous catalyst for the cyclopropanation of styrene, with high
trans cyclopropane diastereoselectivity and was recycled and reused for three consecutive cycles
without a significant loss of catalytic activity.
Article history:
Received 11 January 2011
Received in revised form
14 June 2011
Accepted 22 June 2011
Available online 29 June 2011
Keywords:
Metal organic framework
Cu(I)
4,40-bipyridine
& 2011 Elsevier Inc. All rights reserved.
Sulfate
Heterogeneous catalysis
1. Introduction
Cu(I), which were synthesized under solvothermal (methanol)
synthetic conditions at relatively high temperature (Z140 1C).
Metal organic frameworks (MOFs) [1–5] with both organic and
inorganic ligands are a type of well-crystallized hybrid materials
[6–8]. Recently these materials have been the subject of increas-
ing studies as potential functional materials owing to their
inorganic structural features analog to those of metal oxides
being tuned with the addition of various organic ligands, leading
Since MOFs are crystalline coordination polymers constituted
by networks of metal ions held in place by multidentate organic
molecules, one of their potential applications is catalysis. They
can be regarded as self supported coordination compounds and,
therefore, may act as heterogeneous catalysts in organic trans-
formations. However, the use of MOFs as heterogeneous catalysts
is an area that is still in its infancy [33]. Several monomeric
coordination copper(I) complexes with nitrogen ligands are active
homogeneous catalysts in the cyclopropanation of alkenes
[34,35]. Cyclopropanes are versatile organic compounds, which
may be converted into a variety of useful products by cleavage of
the strained three-membered ring [35].
to the improvement of their original properties. Copper(I) (Cuþ
)
ions possesses a filled 3d shell, thus showing diamagnetic and
photo-luminescent properties [9] with the well known MLCT
(metal–ligand charge transfer) mechanism. But inorganic cuprous
salts, such as cuprous sulfate, are usually unstable in air and are
easily converted into cupric salts in the presence of water or
moisture, and so some organic species (e.g. bpy or phen) may be
used to stabilize cuprous salts and enhance the initial properties
of the inorganic cuprous salts.
In fact, the SO24ꢁ group is a good linker, which can donate its
one [10–13], two [14–17], three [6,18–20] and even four [21–23]
oxygen atoms to connect to metals. Hence, the SO24ꢁ group is a
good candidate for building novel ‘hybrid’ MOFs, with mixed
organic and inorganic linkers. Copper(I) can adopt 3 [24,25] and
4 [14,26] coordination numbers with N-containing bridging ligands
into catena polymeric frameworks. There are several reports on the
Cu-(4,40-bpy)-SO4 system, but most deal with Cu(II) [16,27–31].
Only two reports [16,32] are available on ‘hybrid’ MOFs containing
Herein, we report a new hybrid MOF in the Cuþ-(4,40-bipyr-
idine)-SO4 system, prepared under hydrothermal conditions with
aspartic acid as the reducing agent, with a monoclinic and
3
˚
relatively large unit cell volume (410,000 A ). The single-crystal
structure database (WebCSD v1.1.1, updated on 2010.10.20) con-
tains a single compound [36] with similar unit cell parameters. The
new Cu(I) MOF (1) was applied as a heterogeneous catalyst in the
cyclopropanation of styrene.
2. Experimental
2.1. Materials
n Corresponding authors.
All reagents are commercially available and were used without
E-mail addresses: fshi@ua.pt (F.-N. Shi), ana.rosa.silva@ua.pt (A.R. Silva).
further purification. Copper (II) sulfate 5-hydrate (CuSO4 ꢀ 5 H2O,
0022-4596/$ - see front matter & 2011 Elsevier Inc. All rights reserved.
doi:10.1016/j.jssc.2011.06.023

F.-N. Shi et al. / Journal of Solid State Chemistry 184 (2011) 2196–2203
2197
Z99.5%, Panreac), 4,40-bipyridine (4,40-bpy, C10H8N2, Z98%, Alfa
Aesar), -aspartic acid ( -asp, C4H7NO4, Z99%, BDH biochemicals).
Copper(II) trifluoromethanosulfonate ([Cu(Otf)2]), 2,2-Bis[2-(4(S)-
tert-butyl-1,3-oxazolinyl)]propane (Box), styrene, n-undecane,
ethyldiazoacetate and phenylhydrazine were purchased from
Aldrich and dichloromethane from Romil.
The reaction mixture was analyzed by GC-FID (using the
internal standard method) on a Varian 450 GC gas chromato-
graph equipped with a fused silica Varian Chrompack capillary
L
L
column CP-Sil 8 CB Low Bleed/MS (15 m ꢂ 0.25 mm id; 0.15
mm
film thickness), using helium as carrier gas. Conditions used:
125 1C (40 min); injector temperature, 200 1C; detector tempera-
ture, 250 1C. The several chromatographic peaks were identified
against commercially available samples and/or by GC–MS (Finnigan
Trace).
2.2. Cu2(4,40-bpy)2SO4 ꢀ 6(H2O), (1)
0.1153 g (0.46 mmol) of copper sulfate, 0.1030 g (0.66 mmol)
of 4,40-bpy and 0.0787 g (0.59 mmol) of
L-asp were added into
2.5. X-ray crystallography
16 mL of distilled water under magnetic stirring. The mixture was
transferred into a 40 mL Teflon-lined autoclave and heated at
120 1C in an oven for 3 days. After natural cooling, the sample was
filtered and washed with 3 ꢂ 50 mL distilled water. Greenish
yellow crystals of (1) were obtained as a pure phase and air-
dried at ambient conditions (0.08 g, yield ca. 54% based on
CuSO4). IR data: 3445 (b), 1630 (m), 1601(s), 1527 (m), 1486 (s),
1409 (s), 1218 (m), 1104 (s), 795 (m), 721 (w), 621 (m), 472 (m).
Complete single-crystal data were collected at 150(2) K on a
Bruker X8 Kappa APEX II charge-coupled device (CCD) area-detector
diffractometer (Mo-K
a
graphite monochromated radiation,
˚
l
¼0.7107 A) controlled by the APEX2 software package [37] and
equipped with an Oxford Cryosystems Series 700 cryostream
monitored remotely using the software interface Cryopad [38].
Images were processed using the software package SAINTþ [39].
Absorption corrections were applied by the multiscan semiempirical
method implemented in SADABS [40]. The structure was solved by
direct method using SHELXS-97 [41] and refined using SHELXL-97
[42]. All non-hydrogen atoms were successfully refined with aniso-
tropic displacement parameters. Hydrogen atoms bound to carbon
were located at their idealized positions by employing the HFIX 43
instruction in SHELXL-97 and included in subsequent refinement
cycles in riding motion approximation with isotropic thermal
displacement parameters (Uiso) fixed at 1.2 Ueq of the carbon atom
to which they were attached. The hydrogen atoms associated with
water molecules were visible in the last difference Fourier maps
synthesis. These atoms have been included in the final structural
2.3. Instrumentation
Powder X-ray diffraction data (PXRD) were collected at ambient
temperature (ca. 298 K) on a X’Pert MPD Philips diffractometer
˚
(Cu-Ka
radiation,
l
¼1.54056 A), equipped with a X’Celerator detec-
tor, curved graphite monochromated radiation and a flat-plate
sample holder, in a Bragg–Brentano para-focusing optics configura-
tion (40 kV, 50 mA). Intensity data were collected in the continuous
scanning mode in the range ca. 51o2yo501. FTIR spectra were
collected using KBr pellets (Aldrich, 99%þ, FTIR grade) on a Mattson
7000 FTIR spectrometer. Thermogravimetric analysis (TGA) was
carried out on a Shimadzu TGA-50, between room temperature
and 700 1C with a heating rate of 5 1C/min, under an air atmosphere,
respectively, with a flow rate of 20 cm3/min. Scanning electron
microscopy (SEM) was performed using a Hitachi Su-70 and energy
dispersive analysis of X-rays spectroscopy (EDS) was carried out on
a Bruker QUANTAX 400 instruments working at 15 kV. Samples
were prepared by deposition on aluminum sample holders by
carbon coating.
˚
models with the O–H distances restrained to 0.82(1) A, in order to
ensure a chemically reasonable geometry for these moieties, and
with Uiso fixed at 1.2 Ueq of the parent oxygen atoms. The detailed
crystallographic data and structural refinement parameters have
been summarized in Table 1. Complete crystallographic data for the
structure reported in this paper have been deposited in the CIF
2.4. Catalysis experiments
Table 1
Summary of crystal data and structure refinement for (1).
The catalytic activity of the Cu(I) MOF in the cyclopropanation
of styrene was tested at room temperature in batch reactors at
atmospheric pressure, with and without constant magnetic stir-
ring. Typically, 5.00 mmol of styrene, 1.80 mmol of n-undecane
and 0.139 g of (1) in 10.0 ml of dichloromethane were used.
Finally, 0.65 ml of ethyldiazoacetate (EDA) was added to the
reaction mixture at a rate 0.32 ml/h over 2 h using a syringe
pump. When the addition of ethyldiazoacetate finished, aliquots
(0.05 ml) were periodically withdrawn from the reaction mixture
Compound
T (K)
(1)
150
Formula
FW
C
20H28Cu2N4O10S
643.60
P2(1)/c
29.107(2)
Space group
˚
a (A)
17.1516(12)
21.5943(15)
˚
b (A)
˚
c (A)
(deg.)
110.371(3)
b
3
10106.1(12)
˚
V (A)
with a hypodermic syringe, filtered through PTFE 0.2 mm syringe
Z
16
filters, and analyzed by GC-FID by the internal standard method.
At the end of the reactions, the solution was removed with a
syringe and then (1) was washed several times with fresh
dichloromethane, dried in air overnight and reused in another
cycle using the same experimental procedure.
In order to compare with the heterogeneous phase reactions,
three homogeneous phase control experiments were also per-
formed using this experimental procedure and: 0.0071 g of 4,4-
bpy (0.045 mmol) and 0.0112 g of copper(II) sulfate (0.045 mmol);
1.0% mol of [Cu(Otf)2] and Box and, finally, no catalyst. Although
the Cu(II) complex with Box is also highly active in the cyclopro-
panation of styrene, phenylhydrazine was added to solution in
order to reduce the Cu(II) homogeneous complex to Cu(I).
Dc (g cmꢁ3
)
1.692
1.827
Absorption coefficient
Crystal size (mm3)
m )
(mmꢁ1
0.22 ꢂ 0.20 ꢂ 0.08
3.56 to 30.51
Theta range for data collection
Index ranges
ꢁ41rhr41, ꢁ24rkr22, ꢁ30rlr30
178,549
Reflections collected
Independent reflections
Completeness to theta
Rint
30,804 [R(int)¼0.0555]
99.8%
0.0555
Data/restraints/parameters
Final R[I42sigma(I)]
R indices (all data)
GOF
30,804/45/1459
R1¼0.0524, wR2¼0.1197
R1¼0.0914, wR2¼0.1376
1.018
ꢁ3
1.669 and ꢁ0.824
˚
D
rmax (min/e A
)

2198
F.-N. Shi et al. / Journal of Solid State Chemistry 184 (2011) 2196–2203
format with the Cambridge Crystallographic Data Center as supple-
mentary publication no. CCDC 805893. Copies of the data can
be obtained free of charge on application to CCDC, 12 Union
Road, Cambridge CB2 1EZ, UK (fax: (44) 1223336-033; e-mail:
hdeposit@ccdc.cam.ac.uk).
irregularly and usually aggregated into big polycrystalline parti-
cles, however, it is possible to find out smaller and qualified single
crystals for characterization. EDS analyses by point method on the
three surface spots of the different crystalline particles for the
same sample give the similar molar ratio Cu:S¼69:31 (66:34;
68:32)E2:1 indicating that Cu here is Cu(I), for charge balance,
which is consistent with the single crystal structure data.
3. Results and discussion
3.1. Structure description
Compound (1) was synthesized via a mild hydrothermal
reaction using aspartic acid as a reductant. This synthetic strategy
shows that an appropriate reducing agent can easily reduce Cu(II)
to Cu(I) under hydrothermal conditions at relatively low tem-
perature (120–130 1C). The final product exhibits the large parti-
cles shown in Fig. 1, being most of them visible by naked eye. The
SEM image of the particles shows the species are formed
Compound (1) forms an infinite double chain network similar to
the one reported in literature [16], which possesses the same
secondary building unit [Cu2(SO4)(4,40-bpy)2]. However, the unit
cell volume of (1) is much larger and the asymmetric unit contains
eight crystallographic unique Cu sites and twenty-four guest water
molecules [Cu2(SO4)(4,40-bpy)2]4 ꢀ 24H2O (Fig. 2) while there are
only two crystallographic independent Cu sites in the material
quoted in [16]. In Fig. 3, each crystallographic independent copper
has similar coordination geometry and chemical environment.
In fact, all copper atoms coordinate to two nitrogen atoms from
4,40-bpy with the bonding distances varying from 1.900(2) to
˚
1.922(2) A and one oxygen atom from a sulfate group with the
˚
bonding distances changing from 2.257(2) to 2.359 A (Table 2),
which are longer than the Cu–N distances. Therefore, each copper
is linked via 4,40-bpy into an infinite chain, while sulfate groups
bridge two neighboring chains via copper nodes into an infinite
double chain network. The rings of 4,40-bpy molecules are some-
what distorted from the plane, the torsion angles as labeled in
Fig. 3 have been included in Table 2. Nevertheless, the two opposite
rings from 4,40-bpy molecules within the double chains are roughly
˚
parallel with the face to face distances of ca. 3.5 A suggesting p–p
stacking interaction between aromatic rings (Fig. 3).
Fig. 4 shows how the infinite chains pack in the structure. As
previously reported [16], the double chains consisting of copper,
4,40-bpy and sulfate groups are further assembled into layers,
with no direct interaction with each other, parallel to the a–c
planes (Fig. 4) with the sulfate groups protruding up-and-down
Fig. 1. SEM image of the crystalline particles of (1).
Fig. 2. Asymmetric unit of (1) contains eight crystallographically independent Cuþ ions, four SO42ꢁ fragments and twenty-four water guest molecules. The labeling scheme
for all non-hydrogen atoms are shown. Atoms are drawn as thermal ellipsoids at the 50% probability level. Hydrogen atoms are omitted for clarity.

F.-N. Shi et al. / Journal of Solid State Chemistry 184 (2011) 2196–2203
2199
Fig. 3. Ball-and-stick view of the copper coordination environments and the secondary building unit indicating
p–p
interaction between the aromatic rings of 4,40-bpy
(distances are depicted close to the arrows pointing to the centers of the aromatic rings).
Table 2
˚
Selected bond distances (A), angles (deg.) and the torsion angles (deg.) for (1).
Cu(1)–N(1)
1.900(2)
Cu(1)–N(2)#1
1.904(2)
Cu(1)–O(1)
2.359(2)
Cu(2)–N(4)#1
Cu(3)–N(6)#2
Cu(4)–N(8)#2
Cu(5)–N(9)
1.914(2)
Cu(2)–N(3)
1.922(2)
Cu(2)–O(2)
2.281(2)
1.910(2)
Cu(3)–N(5)
1.916(2)
Cu(3)–O(6)
2.257(2)
1.900(3)
Cu(4)–N(7)
1.912(2)
Cu(4)–O(5)
2.273(2)
1.906(2)
Cu(5)–N(10)#2
Cu(6)–N(11)
1.915(2)
Cu(5)–O(10)
2.262(3)
Cu(6)–N(12)#2
Cu(7)–N(14)#1
Cu(8)–N(15)
1.908(2)
1.912(2)
Cu(6)–O(9)
2.261(2)
1.900(3)
Cu(7)–N(13)
1.907(2)
Cu(7)–O(13)
2.334(2)
1.906(2)
Cu(8)–N(16)#1
S(1)–O(2)
1.910(2)
Cu(8)–O(14)
2.334(2)
S(1)–O(4)
1.466(2)
1.474(3)
S(1)–O(3)
1.476(2)
S(1)–O(1)
1.481(3)
S(2)–O(8)
1.464(2)
S(2)–O(7)
1.480(2)
S(2)–O(6)
1.482(2)
S(2)–O(5)
1.483(2)
S(3)-O(11)
1.466(2)
S(3)–O(10)
1.468(3)
S(3)–O(12)
1.473(2)
S(3)–O(9)
1.487(3)
S(4)–O(16)
1.463(3)
S(4)–O(15)
1.471(3)
S(4)–O(13)
1.476(3)
S(4)–O(14)
1.481(3)
N(1)–Cu(1)–N(2)#1
N(4)#1–Cu(2)–N(3)
N(6)#2–Cu(3)–N(5)
N(8)#2–Cu(4)–N(7)
N(9)–Cu(5)–N(10)#2
N(12)#2–Cu(6)–N(11)
N(14)#1–Cu(7)–N(13)
N(15)–Cu(8)–N(16)#1
O(4)–S(1)–O(2)
O(4)–S(1)–O(1)
O(8)–S(2)–O(7)
O(8)–S(2)–O(5)
O(11)–S(3)–O(10)
O(11)–S(3)–O(9)
O(16)–S(4)–O(15)
O(16)–S(4)–O(14)
S(1)–O(1)–Cu(1)
S(2)–O(6)–Cu(3)
S(4)–O(13)–Cu(7)
163.08(11)
160.27(12)
161.14(11)
161.90(11)
159.96(12)
160.51(11)
163.67(12)
162.62(12)
109.06(16)
109.68(14)
110.21(14)
109.83(13)
109.37(18)
109.69(15)
110.93(19)
108.64(16)
129.95(14)
122.38(14)
128.07(15)
N(1)–Cu(1)–O(1)
N(4)#1–Cu(2)–O(2)
N(6)#2–Cu(3)–O(6)
N(8)#2–Cu(4)–O(5)
N(9)–Cu(5)–O(10)
N(12)#2–Cu(6)–O(9)
N(14)#1–Cu(7)–O(13)
N(15)–Cu(8)–O(14)
O(4)–S(1)–O(3)
O(2)–S(1)–O(1)
O(8)–S(2)–O(6)
O(7)–S(2)–O(5)
O(11)–S(3)–O(12)
O(10)–S(3)–O(9)
O(16)–S(4)–O(13)
O(15)–S(4)–O(14)
S(1)-O(2)–Cu(2)
S(3)–O(9)–Cu(6)
S(4)–O(14)–Cu(8)
99.28(9)
N(2)#1–Cu(1)–O(1)
N(3)–Cu(2)–O(2)
N(5)–Cu(3)–O(6)
N(7)–Cu(4)–O(5)
N(10)#2–Cu(5)–O(10)
N(11)–Cu(6)–O(9)
N(13)–Cu(7)–O(13)
N(16)#1–Cu(8)–O(14)
O(2)–S(1)–O(3)
O(3)–S(1)–O(1)
O(7)–S(2)–O(6)
O(6)–S(2)–O(5)
O(10)–S(3)–O(12)
O(12)–S(3)–O(9)
O(15)–S(4)–O(13)
O(13)–S(4)–O(14)
S(2)–O(5)–Cu(4)
S(3)–O(10)–Cu(5)
97.01(9)
100.36(11)
99.36(10)
101.59(10)
100.67(11)
100.63(10)
98.44(10)
101.11(10)
109.77(14)
109.80(15)
110.05(14)
108.63(14)
109.97(15)
109.80(16)
108.69(15)
109.97(16)
138.30(17)
124.18(15)
139.68(16)
98.60(10)
98.96(10)
95.94(10)
98.94(11)
98.22(9)
96.98(10)
95.64(10)
109.26(14)
109.25(15)
108.64(13)
109.46(14)
109.08(15)
108.91(15)
108.78(17)
109.82(15)
144.54(15)
145.69(19)
Selected torsion angles (deg.)
C(4)–C(3)–C(8)–C(7)
173.9(3)
C(14)–C(13)–C(18)–C(17)
C(42)–C(43)–C(48)–C(49)
175.3(3)
170.8(3)
C(22)–C(23)–C(28)–C(29)
C(52)–C(53)–C(58)–C(59)
C(74)–C(73)–C(78)–C(77)
ꢁ162.6(3)
169.3(3)
C(32)–C(33)–C(38)–C(39)
C(64)–C(63)-C(68)–C(67)
ꢁ157.2(3)
ꢁ153.7(3)
ꢁ150.6(3)
Symmetry transformations used to generate equivalent atoms: #1 x, ꢁyþ1/2, zꢁ1/2; #2 x, ꢁyþ3/2, zꢁ1/2.
into the interlayer space. Almost all coordinated and uncoordi-
nated oxygen atoms from these sulfate groups form complicated
hydrogen-bonding networks with a variety of guest water mole-
cules as shown in Fig. 5.
via sulfate groups as bridges extending into an infinite plane by
hydrogen bonding (Fig. 6 and Table 3), eventually leading to the
formation of a supramolecular 3-D framework of (1).
In order to highlight the hydrogen bonding networks in (1), the
3.2. Thermal properties
copper and 4,40-bpy have been removed from Fig.
5 and
the structure rotated by 901, giving Fig. 6 showing a hydrogen
bonding interaction plane. This plane consists of two chains
self-assembled by the lattice water guests further linking together
The thermal stability of (1) was studied in air from room
temperature to 700 1C. In this range, the TGA plot of (1) exhibits
several weight loss steps due to the removal of lattice water and

2200
F.-N. Shi et al. / Journal of Solid State Chemistry 184 (2011) 2196–2203
Fig. 4. Packing diagram of (1) viewing along a axis showing bonded sulfate groups from different chains layers protruding up-and-down into the interlayer space.
Guest water molecules in between the layers are omitted for clarity.
Fig. 5. Ball-and-stick representation of the unit cell of (1) viewed along the c axis. C and N are displayed in wireframe. Hydrogen bonding among guest water molecules
and sulfate groups between the double chains are depicted by dotted lines, and lead to the formation of a 3-D supramolecular framework.
4,40-bpy molecules (Fig. 7). From room temperature to 100 1C,
only partial (ca. 10%) water is released that is comparable with
the thermal behaviors reported in literatures [25,27,31] indicating
the different stability of the lattice water molecules with com-
prehensive hydrogen bonding interaction, while the full removal
of the guest water molecules occurs at ca. 195 1C. The total
amount of 16.99% of all water molecules are removed from the
lattice, which is consistent with the calculated value of 16.78%
due to breaking of hydrogen bonding interaction. From 195 to
460 1C the plot is composite, suggesting that the loss of 4,40-bpy is
complex possibly due to the presence of several different coordi-
nation environment for 4,40-bpy. The total weight loss of 50.00%
from 195 to 460 1C is in fair agreement with the calculated value
of 48.48% due to decomposition of the network and releasing of
the 4,40-bpy molecules that is similar to the thermal decomposi-
tion temperature of 4,40-bpy reported in the literature [25,31] but
Fig. 6. Network of hydrogen bonding among water guests and sulfate groups to
different from that of [27] in which the study was performed
form an infinite layer. H?O bonds are depicted in cyan, while the H?S bonds are
under nitrogen atmosphere. Although there is no weight loss from
460 to 600 1C, above 600 1C there is again new weight loss due to
colored in pink for clarity. (For interpretation of the references to color in this
figure legend, the reader is referred to the web version of this article.)

F.-N. Shi et al. / Journal of Solid State Chemistry 184 (2011) 2196–2203
2201
Table 3
Hydrogen bonds for (1).
D–HyA
d(D–H)
d(HyA)
d(DyA)
o(DHA)
O(17)–H(17A)yO(10)#5
O(17)–H(17A)yS(3)#5
O(17)–H(17B)yO(33)#6
O(18)–H(18A)yO(35)
O(18)–H(18B)yO(5)#7
O(18)–H(18B)yS(2)#7
O(19)–H(19A)yO(20)
O(19)–H(19B)yO(18)#8
O(20)–H(20A)yO(8)
O(21)–H(21A)yO(28)#4
O(21)–H(21B)yO(1)#7
O(21)–H(21B)yS(1)#7
O(22)–H(22A)yO(36)#2
O(22)–H(22B)yO(40)
O(23)–H(23A)yO(15)
O(23)–H(23B)yO(22)
O(24)–H(24A)yO(3)
O(24)–H(24B)yO(12)
O(25)–H(25A)yO(12)
O(25)–H(25B)yO(3)
O(26)–H(26B)yO(14)
O(27)–H(27A)yO(22)#6
O(27)–H(27A)yO(23)#6
O(27)–H(27B)yO(13)
O(27)–H(27B)yS(4)
0.813(19)
0.813(19)
0.812(19)
0.808(19)
0.829(19)
0.829(19)
0.82(2)
2.24(2)
2.96(4)
1.94(2)
2.20(4)
2.01(2)
3.00(3)
1.92(3)
2.06(3)
2.15
3.040(5)
3.629(3)
2.753(5)
2.852(4)
2.832(4)
3.775(3)
2.709(5)
2.855(6)
2.765(4)
2.824(7)
2.814(5)
3.770(4)
2.755(7)
2.872(7)
2.909(5)
2.910(7)
2.809(4)
2.812(4)
2.848(4)
2.814(4)
2.891(5)
2.992(7)
3.509(5)
2.833(5)
3.710(4)
2.750(5)
2.749(5)
2.852(6)
2.804(5)
2.804(4)
3.729(3)
3.027(6)
2.771(4)
2.715(6)
2.716(6)
2.712(7)
2.789(4)
2.699(6)
2.824(5)
2.775(4)
2.786(4)
3.748(3)
2.781(5)
2.763(5)
2.792(6)
2.833(4)
3.683(3)
2.793(4)
2.768(5)
2.737(4)
2.714(4)
3.749(3)
3.188(5)
2.810(5)
2.877(4)
3.675(4)
167(5)
142(5)
176(6)
137(5)
171(5)
157(5)
161(7)
162(8)
131.1
0.83(2)
0.83
0.78(2)
2.09(3)
2.02(3)
2.99(3)
1.94(2)
2.02(3)
2.06
155(7)
168(8)
165(7)
171(8)
167(7)
179.8
0.80(2)
0.80(2)
0.82(2)
0.87(2)
0.85
0.84
2.07
177.7
0.833(19)
0.830(19)
0.825(19)
0.850(19)
0.82(2)
2.00(2)
1.99(2)
2.05(2)
1.97(2)
2.10(3)
2.40(5)
2.56(2)
1.95(2)
2.91(4)
1.95(2)
1.94(2)
2.07(3)
2.05(4)
2.01(2)
2.96(3)
2.34(4)
1.98(3)
1.98(3)
1.95(4)
2.08(7)
1.99(2)
2.00(3)
2.00(2)
1.95(2)
1.98(2)
3.00(3)
1.96(2)
1.92(2)
2.13(4)
2.00(2)
2.96(3)
1.97(2)
2.05(3)
2.00(2)
1.87(2)
2.94(2)
2.40(3)
2.31
162(4)
172(5)
164(4)
170(4)
163(6)
119(4)
167(4)
169(5)
150(5)
171(6)
167(6)
163(8)
154(7)
164(5)
157(5)
143(5)
163(6)
150(6)
153(8)
133(8)
170(5)
150(5)
165(5)
174(5)
173(5)
154(4)
178(5)
169(6)
138(5)
170(5)
146(4)
162(5)
155(5)
158(5)
173(5)
162(4)
158(4)
119.0
Fig. 7. Thermogram of (1) in air.
0.965(19)
0.965(19)
0.895(19)
0.895(19)
0.806(19)
0.824(19)
0.81(2)
O(28)–H(28A)yO(38)#2
O(28)–H(28B)yO(24)#9
O(29)–H(29A)yO(26)
O(29)–H(29B)yO(9)
O(30)–H(30A)yO(16)
O(30)–H(30A)yS(4)
0.81(2)
0.820(19)
0.820(19)
0.811(19)
0.821(19)
0.808(19)
0.83(2)
O(30)–H(30B)yO(26)
O(31)–H(31A)yO(16)
O(31)–H(31B)yO(19)#6
O(32)–H(32A)yO(34)
O(32)–H(32B)yO(29)
O(33)–H(33A)yO(11)
O(33)–H(33B)yO(32)
O(34)–H(34A)yO(30)
O(34)–H(34B)yO(7)#7
O(35)–H(35A)yO(7)#7
O(35)–H(35A)yS(2)#7
O(35)–H(35B)yO(31)
O(36)–H(36A)yO(25)#4
O(36)–H(36B)yO(26)#4
O(37)–H(37A)yO(6)#7
O(37)–H(37A)yS(2)#7
O(37)–H(37B)yO(39)
O(38)–H(38A)yO(17)#6
O(38)–H(38B)yO(37)
O(39)–H(39A)yO(4)#7
O(39)–H(39A)yS(1)#7
O(39)–H(39B)yO(28)#4
O(40)–H(40A)yO(20)
O(40)–H(40B)yO(2)
0.83(2)
0.812(19)
0.780(19)
0.843(19)
0.827(19)
0.815(19)
0.815(19)
0.816(19)
0.849(19)
0.82(2)
0.844(19)
0.844(19)
0.850(19)
0.768(18)
0.781(18)
0.847(19)
0.847(19)
0.832(19)
0.83
Fig. 8. PXRD patterns of (1). Top: simulated from single crystal data; middle:
experimental pattern of the as-synthesized sample; bottom: experimental pattern
after four catalytic cycles.
crystals, the by-product of the cyclopropanation reaction (Fig. 9).
A 20% conversion of styrene into cyclopropane after 24 h was
detected by GC with 72%, trans diastereoselectivity, slightly
higher than in the homogeneous phase reaction with the best
catalyst available (CuBox) for this reaction (Table 4). Likewise to
this homogeneous catalyst [34], the cyclopropanation actives
sites in the MOF are the copper(I) centres with N2O2 coordination
sphere, from two independent 4,40-bipyridine molecules and two
sulphate molecules. Although the mechanism of the copper
catalyzed cyclopropanation reactions is still not fully understood
it is generally accepted that this reaction proceeds via a copper–
carbene complex formed upon coordination of the EDA and
consequent loss of nitrogen [43]. Hence the MOF copper(I) centre
has still free coordination sites and allows the formation of the
carbene intermediate.
0.83
2.07
162.3
O(40)–H(40B)yS(1)
0.83
3.01
138.2
Symmetry transformations used to generate equivalent atoms: #1x, ꢁyþ1/2,
zꢁ1/2; #2 x, ꢁyþ3/2, zꢁ1/2; #3 x, ꢁyþ1/2, zþ1/2; #4 x, ꢁyþ3/2, zþ1/2;
#5xþ1, y, z; #6 ꢁxþ1, ꢁyþ1, ꢁzþ1; #7x, y, zþ1; #8 x, y, zꢁ1; #9ꢁx, yþ1/2,
ꢁzþ1/2.
the complicated decomposition of the sulfate groups and
oxidation–reduction of cuprous ion [25], which will not be
discussed here.
3.3. Catalytic studies
In the second cycle the liberation of nitrogen was not as strong
as in the first catalytic cycle and the reaction took twice the time
to achieve a comparable styrene conversion (23%), although with
the same diastereoselectivity (72%). In the 3rd cycle the strong
liberation of nitrogen was again observed and the styrene con-
version obtained in 24 h was similar to that of the 1st cycle, with
The purity of the bulk sample (1) for catalytic studies was
proved via PXRD analysis (Fig. 8). After 45 min of addition of EDA
at 0.32 ml/h rate to the solution containing styrene and (1), strong
liberation of nitrogen gas was observed at the surface of the MOF

2202
F.-N. Shi et al. / Journal of Solid State Chemistry 184 (2011) 2196–2203
Fig. 9. Cyclopropanation of styrene with ethyldiazoacetate.
(more yellowish), the PXRD pattern of the former (Fig. 8) shows
the presence of (1).
Table 4
Results of the cyclopropanation of styrene with EDA using the Cu(I) MOF as
catalyst.a
f
Run t (h) %Cub %Cc %transc,d
TONe TOF (hꢁ1
)
4. Conclusions
F
C
This work reports the synthesis, structure and catalytic activity of
a new ‘hybrid’ MOF with mixed organic and inorganic linkers, in the
Cu(I) MOFg
Cu(I) MOFh
1st
24
48
0.9
0.9
20
23
19
18
20
9
51
55
62
54
58
46
57
52
57
72
72
73
66
73
67
60
66
71
23
27
22
21
0.97
0.56
0.92
0.19
2nd
3th
4th
1st
copper-(4,40-bpy)-sulfate system. With a suitable reductant,
L-aspar-
24
tic acid, we have successfully prepared a Cu(I) supramolecular MOF,
110
28
[Cu2(SO4)(4,40-bipy)2]4 ꢀ 24H2O, under mild hydrothermal condi-
3
˚
2nd
96
tions. The volume (10106.1 A ) of the unit cell of (1) is relatively
No catalyst
CuSO4þ4,40-bpy
CuBox
24
7
considerable, much larger than the volume of a similar structure
110
3
0.9
1.0
7
3
˚
previously reported [16] (2519.34 A ) although both materials have
93
95
32
the same secondary building unit. The structure of (1) consists of
Cu(I) nodes linked by 4,40-bpy into infinite chains, and sulfate
groups connecting two neighboring chains, resulting in a 1-D double
chain network. Guest water molecules establish a complicated
network of hydrogen bonding interactions with their neighboring
oxygen and sulfur atoms, leading to the formation a 3-D supramo-
lecular framework. (1) was tested as a heterogeneous catalyst in the
cyclopropanation of styrene showing a high trans cyclopropane
diastereoselectivity and could be recycled and reused for three
consecutive cycles without significant loss of catalytic activity.
a
Reactions performed at room temperature using 5.00 mmol styrene,
1.80 mmol n-undecane (internal standard), 139 mg of MOF and 5.50 mmol of
EDA in 10.0 ml of CH2Cl2.
b
Cu molar% relatively to styrene.
c
Determined by CG-FID.
d
%trans ¼trans ꢂ 100/(transþcis); F¼diethyl fumarate, trans by-product from
the dimerization of EDA (cis¼diethyl maleate); C¼cyclopropane.
e
TON¼moles of styrene converted/moles of Cu.
f
TOF¼TON/time of reaction.
g
Reaction performed without constant stirring.
h
Reaction performed under constant magnetic stirring at 1000 rpm.
a slightly higher trans cyclopropane diastereoselectivity (73%).
In the next cycle the reaction slowed down and comparable
styrene conversion was achieved only after 110 h with decrease
in the trans cyclopropane diastereoselectivity (66%).
It is noteworthy that the reaction was also performed under
constant stirring conditions with similar catalytic performance as
without stirring but in the second cycle the activity was much
lower than without stirring, which may be due to the difficult
recycling of the crushed MOF crystals.
Acknowledgments
~
ˆ
We acknowledge Fundac-ao para a Ciencia e a Tecnologia (FCT) for
funding (PTDC/QUI/ 65805/2006, FCOMP-01–0124-FEDER-007424)
and Fundo Social Europeu. F.-N. SHI and A.R. Silva acknowledge FCT
ˆ
for Ciencia 2007 and 2008 programs, respectively.
Appendix A. Supplementary material
In the control experiment using comparable amounts of
copper(II) sulfate (0.9% mol) and 4,40-bpy (0.9% mol) as those
contained in MOF (1) catalytic reactions styrene conversion after
110 h was similar to the control experiment where no catalyst
was used. Hence, the catalytic reactions with (1) were truly
heterogeneous and any copper leaching into the solution was
not responsible for the observed MOF (1) activity in the cyclo-
propanation reaction.
It is worth to mention that three copper(I) complexes with
2,20-bipyridine and styrene were already reported to be homo-
geneous catalysts in the cyclopropanation of styrene [43]. Cyclo-
propane diastereoselectivities of 68.2, 69.9 and 82.0, depending
on the counterion coordinated and complex structure, can be
calculated from the results presented in this paper using a
different product analysis methodology. Therefore the present
copper(I) MOF is more diastereoselective than most of these
reported homogeneous copper(I) complexes.
Supplementary material associated with this article can be
found in the online version at doi:10.1016/j.jssc.2011.06.023.
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