A polyoxometalate-encapsulating cationic metal-organic framework as a heterogeneous catalyst for desulfurization

Article abstract of DOI:10.1002/chem.201405825

A new cationic triazole-based metal-organic framework encapsulating Keggin-type polyoxometalates, with the molecular formula [Co(BBPTZ)₃][HPMo₁₂O₄₀]·24H₂O [compound 1; BBPTZ = 4,4′-bis(1,2,4-triazol-1-ylmethyl)biphenyl] is hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, powder X-ray diffraction, and single-crystal X-ray diffraction. The structure of compound 1 contains a non-interpenetrated 3D CdSO₄ (cds)-type framework with two types of channels that are interconnected with each other; straight channels that are occupied by the Keggin-type POM anions, and wavelike channels that contain lattice water molecules. The catalytic activity of compound 1 in the oxidative desulfurization reaction indicates that it is not only an effective and size-selective heterogeneous catalyst, but it also exhibits distinct structural stability in the catalytic reaction system.

Full text of DOI:10.1002/chem.201405825

DOI: 10.1002/chem.201405825
Full Paper
&
Metal–Organic Frameworks
Polyoxometalate-Encapsulating Cationic Metal–Organic
Framework as a Heterogeneous Catalyst for Desulfurization
[a, b]
[a]
[a]
[a]
[a]
Xiu-Li Hao,
Yuan-Yuan Ma, Hong-Ying Zang,* Yong-Hui Wang, Yang-Guang Li,* and
[a]
En-Bo Wang
Abstract:
A
new cationic triazole-based metal–organic
trated 3D CdSO4 (cds)-type framework with two types of
channels that are interconnected with each other; straight
channels that are occupied by the Keggin-type POM anions,
and wavelike channels that contain lattice water molecules.
The catalytic activity of compound 1 in the oxidative desul-
furization reaction indicates that it is not only an effective
and size-selective heterogeneous catalyst, but it also exhibits
distinct structural stability in the catalytic reaction system.
framework encapsulating Keggin-type polyoxometalates,
with the molecular formula [Co(BBPTZ) ][HPMo O ]·24H O
3
12 40
2
[compound 1;
BBPTZ=4,4’-bis(1,2,4-triazol-1-ylmethyl)bi-
phenyl] is hydrothermally synthesized and characterized by
elemental analysis, IR spectroscopy, thermogravimetric analy-
sis, powder X-ray diffraction, and single-crystal X-ray diffrac-
tion. The structure of compound 1 contains a non-interpene-
Introduction
units and MOF units with value-added functionalities, such as
size-selective catalysis. Additionally, such POM@MOF materials
can be easily recycled after catalytic reactions. To synthesize
POM@MOF materials, a routine method is direct impregnation
of MOFs into POM solution, but this method may not always
work well, due to the mismatch between POMs and MOFs in
size, charge, structural symmetry, solubility, and pH stability. To
date, only a few MOFs, such as MIL-101, HKUST-1 and NENU-
11, have been successfully loaded with guest POM cata-
Metal–organic frameworks (MOFs) have emerged as a class of
state-of-the-art materials with designable and multiple func-
tionalities. In this research field, the scope for employment of
functional organic linkers in MOFs and the encapsulation of
different active entities, such as metal or metal oxide nanopar-
ticles or luminescent, dye, and medicine molecules, within
their channels have led to the development of MOFs for
a wide variety of uses, such as catalysis, luminescence, molecu-
[18–20]
lysts.
Another synthetic strategy is to use POMs as nodes
[
1–10]
lar detection, or drug delivery.
Introducing polyoxometa-
or linkers connecting with metal–organic coordination moiet-
[21,22]
lates (POMs) into MOF systems to obtain POM-encapsulating
MOF (POM@MOF) composite materials is one such hot topic in
ies, to form the POM-based MOFs.
The surface oxygen
atoms of POM units in the POM-based MOFs are partially occu-
pied by the metal–organic fragments, which might limit the
catalytic properties of the POM units. A third way is to employ
POMs as templates, metal ions as nodes, and organic function-
al groups as linkers to construct POM@MOF hybrid compounds
[
11]
this field. POMs, as a type of nanoscale metal–oxo cluster,
have been shown to exhibit activity in acidic, redox, photo-,
and electro-induced catalysis. However, POMs’ main drawback
from the point of view of heterogeneous catalysis is their rela-
[
12–17]
[23]
tively low specific surface area (SSA).
Therefore, the intro-
in situ. One possible disadvantage of this hybrid material is
[24]
duction of such nanoscale molecular catalysts into micropo-
rous MOFs brings about the following advantages: i) Improve-
ment of their SSA; ii) uniform dispersal of POM units within
a MOF skeleton at the molecular level; iii) affording both POM
that the voids of MOFs can be fully occupied by POM units.
Thus, construction of new POM@MOF hybrid materials while
keeping the voids not fully occupied remains a challenge. To
be an ideal loading medium for POMs, MOFs should exhibit
several properties, as follows: i) MOFs should stably load POMs
without loss or framework-collapse during the reaction;
ii) POM@MOF materials should retain porous structural features
for the entrance and reaction of various substrates; iii) MOFs
should be able to improve the loading content of POM cata-
lysts. A promising way to fulfill the above requirements is the
construction of cationic MOFs, which can strongly interact with
anionic POM units by virtue of electrostatic forces. In this
regard, an optimal synthetic route is the use of desired anionic
POM catalysts as templates to construct the cationic MOF host
in situ with transition metal ions and suitable neutral bridging
ligands.
[a] Dr. X.-L. Hao, Y.-Y. Ma, Prof. H.-Y. Zang, Dr. Y.-H. Wang, Prof. Y.-G. Li,
Prof. E.-B. Wang
Key Laboratory of Polyoxometalate Science of Ministry of Education
Faculty of Chemistry, Northeast Normal University
Changchun, 130024 (P.R. China)
E-mail: zanghy100@nenu.edu.cn
liyg658@nenu.edu.cn
[b] Dr. X.-L. Hao
School of Chemical and Biological Engineering
Tai Yuan Science and Technology University
Taiyuan, 030021 (P. R. China)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201405825.
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+
During our investigation of new POM-encapsulating MOF
materials, we chose a neutral N-donor semirigid bridging
ligand, 4,4’-bis(1,2,4-triazol-1-ylmethyl)biphenyl (BBPTZ). The
triazole groups in this ligand usually display strong coordina-
tion ability with transition metal ions. Furthermore, the length
of BBPTZ ligand is approximately 15.4 ꢁ, which is much longer
than the typical Keggin-type POM units (ca. 10 ꢁ; Figure 1).
The semirigidity of the ligand endowed the flexibility and elas-
tic ability of pores according to different templates. Therefore,
Co center (see the Supporting Information, Figure S1). This
Co center exhibits a hexacoordinated environment with six ni-
trogen atoms from the triazole groups of six BBTZ ligands (Fig-
ure S1). The CoꢀN bond lengths range from 2.136(7) to
2.208(7) ꢁ and the N-Co-N bond angles vary from 87.0(3)8 to
180.0(4)8. In this cationic MOF unit, the bridging BBPTZ ligands
exhibit two types of configurations, that is, the “U”-type (LU)
and “S”-type (L ) configurations (Figure 2a and Figure S2). Each
S
BBTPZ ligand connects with two Co centers. Based on above
coordination modes and structural configurations, the Co cen-
Figure 2. a) Ball-and-stick view of the three basic building units in the cat-
ionic 3D MOF of 1; b) the cationic 3D cds-type MOF in 1 with two types of
channels viewed along c axis; c) schematic view of the non-interpenetrating
cds-type framework in 1.
Figure 1. Schematic view of the sizes of Keggin-type POM unit (top) and
BBPTZ ligand (below).
BBPTZ ligand can be a potential precursor for in situ construc-
tion of MOFs encapsulating Keggin-type POM units. Herein, we
ters are connected with four L ligands to form 1D loop-con-
U
report
a
new POM-encapsulating MOF compound,
taining chains (Figure 2a). These loop-containing chains are
parallel to each other on the ab plane, but the orientations of
the chains on two neighboring ab planes are perpendicular to
each other. These loop-containing chains on adjacent ab
[Co(BBPTZ) ][HPMo O ]·24H O (1). Compound 1 contains
3
12 40
2
a cationic 3D CdSO (cds)-type MOF host with two types of
4
channels that are interconnected with each other; linear chan-
nels that are occupied with the Keggin-type POM anions and
wavelike channels that are occupied by lattice water mole-
cules. Compound 1 represents the first microporous
POM@MOF hybrid compound composed of cationic triazole-
planes are further linked together by L ligand via the Co cen-
S
ters, forming a 3D open framework (Figure 2b and Figure S3 in
the Supporting Information). From the topological viewpoint,
the two parallel BBPTZ ligands in one loop unit can be consid-
ered as one linker and the Co centers can be reduced to
a four-connected node. Thus, the whole framework adopts the
[
25]
based MOF and anionic Keggin-type POM units. Oxidative
desulfurization is employed as a model catalytic reaction to in-
vestigate the catalytic properties of compound 1, as well as its
stability in the organic catalytic reaction system.
5
CdSO4 (cds) topology, a 4-connected {6 .8} net (Figure 2c).
Most cds-type frameworks are interpenetrated due to the self-
[26,27]
duality of the cds net.
However, compound 1 is a rare ex-
ample of a cds-type framework without an interpenetrating
feature. The encapsulation of large polyoxoanions in the cds-
type net may be an important factor in avoiding
interpenetration.
Results and Discussion
Crystal Structure of 1
Compound 1 crystallizes in the monoclinic space group C2/c,
The cds-type framework of 1 contains two kinds of channels
viewed along c axis (Figures 2b and 3a). Channel A is straight
and filled with the Keggin-type POMs, whereas channel B is un-
dulated and occupied by lattice water molecules (Figure 3b
and Figure S4). The window size of channel B is ca. 11.34(1)ꢂ
10.87(1) ꢁ. Furthermore, channels A and B are inter-connected
with each other, suggesting that the guest molecules in chan-
nel B may have the chance to contact with POM units in chan-
and the structural unit contains a cationic 3D MOF motif
II
2+
[
Co (BBPTZ) ] ,
the
a-Keggin-type
polyoxoanion
3
2
ꢀ
[
HPMo O ] , and lattice water molecules. Co ion possessing
12
40
the +2 oxidation state is confirmed by the X-ray photoelectron
spectra (XPS; see the Supporting Information, Figure S5) and
the bond valence sum (BVS) calculations (Table S2). In 1, the
cationic MOF possesses one crystallographically independent
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catalysts into MOFs is a new route to develop a heterogeneous
catalyst system. Herein, the oxidative desulfurization reaction
model is used to evaluate the catalytic activity, size selectivity,
and stability of compound 1 as a heterogeneous catalyst.
Before the catalytic investigation, the solubility and stability
of compound 1 were investigated. Compound 1 was found to
be insoluble in various common solvents including water,
methanol, ethanol, acetonitrile, and dichloromethane. After im-
mersing compound 1 into the above solvents for 24 h, no sig-
nals could be observed from the UV/Vis spectra (see the Sup-
porting Information, Figure S6). The thermogravimetric (TG)
analysis curve of compound 1 showed a quite flat stage after
all lattice water molecules were removed at 1408C, suggesting
that the framework could be stable after losing the guest
water molecules (see the Supporting Information, Figure S7).
Based on this experimental result, compound 1 was further
treated by heating at 1408C under vacuum for 8 h. The
powder X-ray diffraction (PXRD) pattern of the heat-treated
sample of 1 was obtained, which was in agreement with that
of untreated compound 1 (Figure 4 and Figure S8 in the Sup-
porting Information). This result further confirmed that the
main framework of compound 1 underwent no change after
Figure 3. a) Ball-and-stick and polyhedral view of the POM@MOF structure
of 1 viewed along c axis; b) the wavelike channel B in the POM@MOF of
1
viewed along a axis. The solvent accessible voids in the channel are mod-
eled with yellow background.
nel A (see the Supporting Information, Figures S3 and S4). Cal-
[
28]
culations with PLATON program indicate that the potential
3
solvent area volume is 1929.7 ꢁ after removal of the solvent
water molecules, equal to 20.1% of the crystal volume
3
9
586.4 ꢁ . It is worth mentioning that most reported micropo-
rous POM@MOF hybrid compounds are based on MOFs con-
[
18–20,23a]
structed by O-donor bridging ligands.
However, com-
pound 1 represents the first microporous POM@MOF com-
posed of cationic triazole-based MOF and anionic Keggin-type
POMs. In light of the porous structural of this POM@MOF ma-
terial, we envisioned that it could be used as a new type of
heterogeneous catalyst.
Figure 4. PXRD patterns of compound 1 in 2q range of 5–308: a) Simulated
pattern; b) as-synthesized sample of 1; c) heat-treated sample of 1 at 1408C
under vacuum.
removing the lattice water molecules. Moreover, the initial sol-
vent sorption isotherm measurement suggested that heat-
treated compound 1 can absorb methanol molecules (see the
Supporting Information, Figure S9). Thus, the above heat-treat-
ed samples of compound 1 were used as the catalysts for the
catalytic reaction.
Catalytic oxidative desulfurization
The desulfurization of fossil fuels is a currently significant task,
which is directly associated with the living environment of
human beings. In this research field, oxidative desulfurization
has been developed as an effective strategy to remove refrac-
tory organosulfur substrates, and a key factor in this aspect is
The catalytic oxidation reaction was performed as follows:
Three different sulfide reactants, thioanisole (MBT), dibenzo-
thiophene (DBT), and 4,6-dimethyldibenzothiophene (4,6-
DMDBT) reacted with the oxidant tert-butyl hydroperoxide
(TBHP) in CH Cl medium at 508C with compound 1 as the het-
[
29–32]
the exploration of new oxidative catalyst systems.
Keggin-
type polyoxomolybdates have proven effective catalysts for ox-
idative desulfurization. However, such catalysts are easily solu-
ble in the catalytic reaction system and thus difficult to recycle,
which limits their application. The introduction of such POM
2
2
erogeneous catalyst (Scheme 1).
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cal composition to compound 1 but incorporates no solvent-
accessible voids in its hybrid crystal structure (see the Support-
ing Information, Figure S20). The catalytic oxidation of MBT
into MBTO/MBTO with compound 1’ achieved a conversion of
2
100% in 50 min, which was obviously slower than the reaction
catalyzed by compound 1 (Table 1 and Figure S10d in the Sup-
porting Information). Such a difference suggests that the cata-
lytic oxidative desulfurization may just happen on the surface
of compound 1’ and only POMs on the surface of the frame-
work play a catalytic role in the reaction. However, the porosity
of compound 1 may lead to the POM units both on the surface
and within the voids acting as catalytic sites, which may accel-
erate the oxidation reaction (Scheme 2).
Scheme 1. Oxidation of sulfides thioanisole (MBT), dibenzothiophene (DBT),
and 4,6-dimethyldibenzothiophene (4,6-DMDBT) to corresponding sulfoxides
and sulfones.
Compound 1 exhibited high catalytic activity for the oxida-
tion of the three sulfide substrates into sulfoxide and sulfone
(
Table 1). The maximum conversions were 100% for MBT,
9.16% for DBT, and 99.14% for 4,6-DMDBT, respectively
Table 1 and Figure S10a–c in the Supporting Information). The
9
(
corresponding oxidized sulfoxide and sulfone products were
confirmed by FT/IR spectroscopy and GC-MS (see the Support-
ing Information, Figures S11–S19).
Table 1. Catalytic oxidation of sulfides to corresponding sulfoxides and
[
a]
sulfones with TBHP.
Scheme 2. Different catalytic reaction routes among the sulfide substrates
and different catalysts, based on the catalytic results. Route I represents cat-
alysis taking place on the surface of catalysts; Route II represents catalysis
taking place within the channels of catalysts.
Entry Sulfide Product
Catalyst
t
Conversion [%]
15 min 100
1
2
3
4
5
6
7
MBT
MBT
MBT
DBT
DBT
MBTO+MBTO
MBTO+MBTO
MBTO+MBTO
DBTO+DBTO
DBTO+DBTO
2
2
2
1
none 300 min 74.04
1’
1
1’
1
1’
50 min 100
2
8 h
9 h
8 h
9 h
99.16
98.1
99.14
98.56
2
The oxidative desulfurization of DBT and DMDBT into rele-
vant sulfoxide and sulfone products with compounds 1 and 1’
were also investigated. The catalytic oxidation of DBT and
DMDBT achieved conversion of approximately 99% in 8 h with
DMDBT DMDBTO+DMDBTO
DMDBT DMDBTO+DMDBTO
2
2
[a] Sulfide (0.4 mmol), TBHP (1.5 mmol) and catalyst (10.0 mg) were mixed
in CH Cl (5 mL) at 508C with continuous stirring. The conversion was ob-
2
2
1
and approximately 98% in 9 h with 1’ (Table 1 and Fig-
tained by HPLC analysis with a UV/Vis detector at l=254 nm using an In-
ertsil SIL-100A C18 column.
ure S10b,c,e,f in the Supporting Information). These experi-
mental results suggest that compounds 1 and 1’ possess quite
similar catalytic activities for the oxidative desulfurization of
DBT and DMDBT. In one regard, such slow oxidation processes
are probably due to the relatively strong antioxidant property
of DBT and DMDBT substrates. However, it is more possible
that the catalytic oxidation of DBT and DMDBT by both 1 and
1’ mainly happens on the surface of these catalysts. Especially
considering the larger sizes of DBT and DMDBT molecules than
MBT molecules, DBT and DMDBT may not easily fit through the
wavelike channels of compound 1 (Scheme 2). In contrast to
As control experiments, oxidation of MBT was also per-
formed with a mixture of Co(OAc) and BBPTZ and without
2
any catalyst, which gave conversions of 77.13% and 74.04%
from MBT to MBTO/MBTO2 in 300 min, respectively (Table 1
and Figure S10g,h in the Supporting Information). The results
indicate that compound 1 is a potentially effective catalyst in
the oxidative desulfurization process and that the main catalyt-
ic center is the POM unit. Furthermore, another POM-templat-
ed organic–inorganic hybrid compound, 1’, with the chemical
other well-known POM@MOF- or POM-based porous materials
II
[19c,30]
formula [Co (HBBTZ)(BBTZ) ][PMo O ] (BBTZ=4,4’-bis(1,2,4-
used for catalytic oxidative desulfurization,
compound 1
2
24b]
.5
12 40
[
triazol-1-ylmethyl)benzene)
was used as a reference catalyst
displays relatively low catalytic activities in the oxidation of
for the oxidation of MBT. Compound 1’ has the similar chemi-
DBT and DMDBT due to the smaller pore size of compound 1
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[
19c,30]
[34]
than those of the previously reported composites.
Thus,
reported methods. Elemental analyses (C, H, N) were performed
on a PerkinElmer 2400 CHN elemental analyzer. The FT-IR spectra
were analyzed on a Mattson Alpha-Centauri spectrometer with KBr
the pore size and volume of MOF units should be another im-
portant factor for the catalytic activity of POM@MOF
composites.
ꢀ
1
pellets in the range of 4000–400 cm . TG analyses were carried
out on a Pyris Diamond TG instrument in flowing N with a heating
2
The effect of the size of catalyst particles on the catalytic ac-
tivity was also checked. When a sample of 1 with an average
particle size of 300 mm was used in the oxidation of MBT, the
conversion was 98.56% in 15 min. Under the same conditions,
a ground sample of 1 with an average particle size of 40 mm
gave a conversion of 100% in 15 min (see the Supporting In-
formation, Figure S21). This result suggests that the size of cat-
alytic sample 1 has no obvious influence on the catalytic
activity.
ꢀ1
rate of 108C·min . The powder X-ray diffraction (PXRD) studies
were performed with a Rigaku D/max-IIB X-ray diffractometer at
a scanning rate of 18 per minute with 2q ranging from 58 to 508,
using CuKa radiation (l=1.5418 ꢁ).
Synthesis
[
Co(BBPTZ) ][HPMo O ]·24H O (1): H PMo O ·24H O (0.6 g,
3 12 40 2 3 12 40 2
ca. 0.3 mmol), Co(OAc) ·4H O (0.087 g, 0.35 mmol), and BBPTZ
0.16 g, 0.5 mmol) were mixed in distilled water (10 mL) and stirred
2
2
(
Compound 1 is insoluble in the reaction system and can be
easily recycled by simple centrifugal separation (see the Sup-
porting Information, Figure S22). Notably, no obvious changes
were observed in the FT/IR spectra, UV/Vis diffuse reflectance
spectra, or powder X-ray diffraction (PXRD) data of com-
pound 1 before and after six catalytic cycles (see the Support-
ing Information, Figures S23–S25), suggesting that the porous
framework of compound 1 is stable in this catalytic reaction
system. Furthermore, the catalytic lifetime of compound 1 was
tested. The recycled catalyst was reused for six cycles and the
conversion was only slightly decreased, suggesting that the
catalytic activity of compound 1 can be well maintained (see
the Supporting Information, Figure S26).
at room temperature for 0.5 h. During this period, the reaction
mixture was adjusted to pH 2.0 with 1.0m NaOH. Then, the suspen-
sion was sealed into a Teflon-lined autoclave, kept under autoge-
nous pressure at 1308C for 3 days, and then slowly cooled to room
temperature. Orange block crystals of 1 were isolated, collected by
filtration, washed with distilled water, and kept in a vacuum desic-
cator (50% yield based on Mo). Selected IR (KBr pellet): n˜ =
3
1
8
446(w), 3113(m), 3030(w), 1612(m), 1522(s), 1438(m), 1403(w),
346 (w), 1281 (s), 1210 (m), 1132 (s), 1057 (s), 1010 (w), 956 (s),
ꢀ1
79 (w), 802 cm
(s); elemental analysis calcd (%) for
C H N O PMo Co: C 19.85, H 2.97, N 7.72; found: C 19.88, H
54
97 18 64
12
2.95, N 7.70. TG curve suggests that compound 1 contains approxi-
mately 24 lattice water molecules (see the Supporting Information,
Figure S6).
X-ray Crystallography
Conclusion
Single-crystal X-ray diffraction data for compound 1 was collected
at 150(2) K on the Bruker Apex CCD diffractometer using graphite
monochromatic MoKa radiation (l=0.71073 ꢁ). A multi-scan ab-
sorption correction was applied. The structure was solved by the
direct method and refined by a full-matrix least-squares method
In summary, a new POM@MOF compound was synthesized,
consisting of a cationic triazole-based MOF encapsulating POM
anions. The heterogeneous catalytic property of the POM@
MOF compound was investigated by using the oxidative desul-
furization reaction model, indicating that compound 1 not
only exhibited effective catalytic activity and size-selective
properties, but also showed distinct structural stability. Further-
more, compound 1 was easily recycled by simple centrifugal
separation. Compound 1 represents a new POM@MOF hybrid
example, which is composed of a cationic porous MOF based
on N-donor ligands and Keggin-type polyoxoanions. Moreover,
the catalytic activities of such POM@MOF composites are not
only dependent on the POM moieties but also the pore size
and volume of the MOF units. Therefore, more POM@MOF
compounds based on Keggin-type POM units with different
components and various in situ-assembled cationic triazole-
based MOF systems with larger pore sizes and volumes could
be explored, so as to obtain new catalytically active POM@
MOF compounds. This work is ongoing in our group.
2
[35,36]
on F using the SHELX-97 crystallographic software package.
During the refinement of 1, non-hydrogen atoms were refined ani-
sotropically except the lattice water molecules. During the aniso-
tropical refinement, some C atoms on the organic ligands possess
the anisotropic displacement parameters (ADP) problem. Thus, the
restrained command ‘ISOR’ was used to restrain such atoms so as
to avoid the ADP problems. Furthermore, the five-membered tria-
zole rings and the six-membered benzene rings in the organic li-
gands are structurally unreasonable, thus, the restrained command
‘AFIX 59/AFIX 0’, ‘AFIX 69/AFIX 0’ and ‘DELU’ were used to fix these
five- and six-membered rings with reasonable structural features.
All above restrained refinement led to a restrained value of 102.
The H atoms on organic C centers were fixed in calculated posi-
tions. H atoms on water molecules cannot be assigned from the
weak reflection peaks but directly included into the final molecular
formula. In the final refinement, only two lattice water molecules
can be assigned from the weak residual peaks. However, the struc-
tural feature suggests that there are still solvent-accessible voids in
the compound. Thus, the SQUEEZE program was further used to
remove the contributions of weak reflection for the crystal data
and a new calculation result 1*.hkl was further used to refine the
Experimental Section
[28]
whole crystal structure. Based on the SQUEEZE calculation re-
sults, elemental analysis, and TG analysis, another twenty two lat-
tice water molecules were directly added in the final molecular for-
mula of compound 1. Crystal data and structure refinement for
compound 1 is listed in Table 2. Selected bond lengths and angles
of 1 are listed in Table S1 in the Supporting Information.
Materials and Methods
All chemicals and organic solvents used for synthesis were of re-
agent grade without further purification. The ligand 4,4’-bis(1,2,4-
triazol-1-ylmethyl)biphenyl (BBPTZ) was synthesized according to
[33]
the literature. H PMo O ·nH O was prepared according to the
3
12 40
2
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M
T [K]
r
3263.68
150(2)
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This work was supported by National Natural Science Founda-
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FULL PAPER
Sulfur no more: A cationic triazole-
based metal–organic framework encap-
sulating Keggin-type polyoxometalates,
with the molecular formula [Co(BBPTZ)3]
&
Metal–Organic Frameworks
X.-L. Hao, Y.-Y. Ma, H.-Y. Zang,*
Y.-H. Wang, Y.-G. Li,* E.-B. Wang
[
HPMo O ]·24H O [BBPTZ=4,4’-
12 40 2
&& – &&
bis(1,2,4-triazol-1-ylmethyl)biphenyl], is
synthesized, characterized and shown
to be active in oxidative desulfurization
catalysis.
Polyoxometalate-Encapsulating
Cationic Metal–Organic Framework as
a Heterogeneous Catalyst for
Desulfurization
&
&
Chem. Eur. J. 2015, 21, 1 – 8
www.chemeurj.org
8
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!