Dodecatungstocobaltate heteropolyanion encapsulation into MIL-101(Cr) metal–organic framework scaffold provides a highly efficient heterogeneous catalyst for methanolysis of epoxides

Article abstract of DOI:10.1002/aoc.4065

A heterogeneous catalyst was synthesized by encapsulation of a Keggin-type heteropolytungstate, potassium dodecatungstocobaltate trihydrate, K₅[CoW₁₂O₄₀]·(Co-POM), into chromium(III) terephthalate (MIL-101). Encapsulation was achieved via a ‘build bottle around ship’ strategy in aqueous media, following a hydrothermal method. The structure of the resulting crystalline solid was characterized using X-ray diffraction, correlated with Fourier transform infrared and UV–visible spectroscopy. The metal content was analysed using optical emission spectroscopy. Transmission electron microscopy was used to measure particle size and N₂ adsorption in a Brunauer–Emmett–Teller instrument to characterize the specific surface area. The catalytic activity was investigated using methanolysis of epoxides under mild conditions as a test reaction. The turnover frequency of the heterogeneous Co-POM@MIL-101 catalyst was more than 20 times higher than that of the homogeneous Co-POM catalyst. The Co-POM@MIL-101 catalyst was reused several times with negligible leaching of Co-POM and with no considerable loss of its initial efficiency. The simplicity of preparation, extraordinary stability and high reactivity make Co-POM@MIL-101 an exceptional catalytic matrix that is easily separable from reaction media.

Full text of DOI:10.1002/aoc.4065

Received: 16 April 2017
DOI: 10.1002/aoc.4065
Revised: 25 July 2017
Accepted: 25 July 2017
F U L L P A P E R
Dodecatungstocobaltate heteropolyanion encapsulation into
MIL‐101(Cr) metal–organic framework scaffold provides a
highly efficient heterogeneous catalyst for methanolysis of
epoxides
1
1
1
Afsaneh Marandi | Shahram Tangestaninejad
| Majid Moghadam
|
1
2
1
1
Valiollah Mirkhani | Adam Mechler | Iraj Mohammadpoor‐Baltork
| Farnaz Zadehahmadi
1
Department of Chemistry, Catalysis
A heterogeneous catalyst was synthesized by encapsulation of a Keggin‐
type heteropolytungstate, potassium dodecatungstocobaltate trihydrate,
K [CoW O ]·(Co‐POM), into chromium(III) terephthalate (MIL‐101). Encap-
Division, University of Isfahan, Isfahan
81746‐73441, Iran
2
La Trobe Institute for Molecular
5
12 40
Sciences, La Trobe University, Bundoora,
VIC 3086, Australia
sulation was achieved via a ‘build bottle around ship’ strategy in aqueous media,
following a hydrothermal method. The structure of the resulting crystalline solid
was characterized using X‐ray diffraction, correlated with Fourier transform
infrared and UV–visible spectroscopy. The metal content was analysed using
optical emission spectroscopy. Transmission electron microscopy was used to
measure particle size and N2 adsorption in a Brunauer–Emmett–Teller
instrument to characterize the specific surface area. The catalytic activity was
investigated using methanolysis of epoxides under mild conditions as a test
reaction. The turnover frequency of the heterogeneous Co‐POM@MIL‐101
catalyst was more than 20 times higher than that of the homogeneous Co‐POM
catalyst. The Co‐POM@MIL‐101 catalyst was reused several times with negligi-
ble leaching of Co‐POM and with no considerable loss of its initial efficiency.
The simplicity of preparation, extraordinary stability and high reactivity make
Co‐POM@MIL‐101 an exceptional catalytic matrix that is easily separable from
reaction media.
Correspondence
Shahram Tangestaninejad, Department of
Chemistry, Catalysis Division, University
of Isfahan, Isfahan 81746‐73441, Iran.
Email: stanges@sci.ui.ac.ir
KEYWORDS
heterogeneous catalyst, heteropolyanion, metal–organic frameworks, methanolysis, MIL‐101(Cr)
1
| INTRODUCTION
for further grafting, functionalization and encapsulation
in the MOF scaffold. Thermal stability of MOFs may
exceed 400 °C, and their chemical resistance is good in
most cases. Due to their versatility, MOFs have found
applications in, for example, gas adsorption and separa-
Metal–organic frameworks (MOFs) are hybrid crystalline
porous materials, in which metal ions or clusters are
interconnected by organic bridging ligands.
bination of organic and inorganic building blocks into
highly ordered and crystalline structures provides an
almost infinite number of materials with fine‐tunable
pore size, shape and structure, which also can be used
[
3]
[1,2]
The com-
[
3–5]
[6]
tion
use as drug carriers and in magnetism.
key areas of application is as scaffolds to immobilize
and sensing, while there are examples of their
[
7]
[8,9]
One of the
[
10–14]
homogeneous catalysts.
For the latter application,
Appl Organometal Chem. 2017;e4065.
wileyonlinelibrary.com/journal/aoc
Copyright © 2017 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.4065

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MARANDI ET AL.
[
42–44]
MOFs can be functionalized at the organic linker, or
catalytic units can be encapsulated into the pore spaces.
In this sense, MOFs hold the promise of allowing
intermediates.
Ring‐opening reactions of epoxides
to achieve β‐substituted alcohols with aromatic and
heteroaromatic nucleophiles provide advantageous
pathways in organic synthesis. In general, these reac-
tions proceed under either basic or acidic conditions.
Several heterogeneous catalysts such as graphite
zirconium‐doped mesoporous silica,
thanide–organic coordination polymer
‘heterogenization’ of many homogeneous catalysts with
[
45]
far‐reaching consequences in industrial chemistry.
Polyoxometalates (POMs) are anionic metal–oxygen
clusters comprised of transition metals such as W, Mo,
Nb and V. POMs provide a large and distinct class of
molecular inorganic materials that exhibit a broad range
[
46]
[47]
oxide,
lan-
and MOF‐
have been evaluated for alcoholysis
[
48]
[
49]
based catalysts
[
15,16]
[17]
of tunable electronic, structural, magnetic,
and catalytic properties.
redox
of epoxides. Jiang and co‐workers have used sulfonic
acid‐functionalized MIL‐101, which also includes both
Lewis acidic and Brønsted acidic sites, for alcoholysis
of various epoxides.
(H PW O ) was encapsulated into MIL‐101 by Wee
[18–21]
Individual properties of
POMs lead to many applications, and POMs are favoured
as catalysts, especially for ‘green’ chemistry due to their
noncorrosive nature, low amount of waste and high
[
50]
Phosphotungstic acid
3
12 40
[22]
[51]
stability.
While POMs are large molecules that form
and co‐workers.
This Lewis acid catalyst has been
clusters of colloidal size range, these are hard to separate
from a solution, and hence in their properties POMs are
closer to homogeneous catalysts. Moreover ‘bulk’ POM
used for methanolysis of styrene epoxide.
In the work presented here, K [CoW O ]⋅3H O
5
12 40
2
(Co‐POM) was encapsulated into MIL‐101, synthesized
in the absence of HF, by a one‐pot procedure to prepare
Co‐POM@MIL‐101 catalyst. The catalytic activity of
Co‐POM@MIL‐101 was investigated in the ring‐opening
reaction of epoxides under mild conditions (Scheme 1).
High activity, short reaction time, facile recovery and
recycling of the catalyst make this new hybrid material
highly advantageous for industrial applications.
2
−1
particles have a low specific surface area (1–5 m g ) that
reduces their turnover frequency (TOF) in catalytic
[23]
applications.
Thus, a specific objective of the develop-
ment of POM catalysis is to acquire stable heterogeneous
catalysts with high surface area to associate the high
activity of POMs with the superiority of heterogeneous
catalysts, such as simple recovery and recycling. To this
end, POMs have been adhered to various supports such
[
24–26]
[27]
[28,29]
as silica surfaces,
zeolite.
titania,
active carbon
and
2
2
| EXPERIMENTAL
[
30]
These supports, however, have serious limita-
tions such as reduction of activity, low catalyst retention
and low capacity for catalyst loading that preclude their
successful application. To overcome these limitations,
recent developments in this field have focused on encap-
.1 | Materials and instrumentation
All reagents were purchased at ACS reagent grade from
Merck or Fluka. Co‐POM was prepared according to the
[31–34]
[52]
sulation of POMs within the cavities of MOFs.
literature.
X‐ray diffraction (XRD) analysis was
When materials are larger than the pores of a support
material, the impregnation method cannot be used. In
this case, there are two strategies for encapsulation in a
porous framework: ‘build ship in bottle’ and ‘build bottle
conducted with a Bruker D8 Advance instrument using
Cu K (λ = 1.5406 Å) radiation. The chemical composition
α
was determined using inductively coupled plasma optical
emission spectroscopy (ICP‐OES), with a Jarrell‐Ash
1100 ICP analyser. Specific surface area, pore volume
and pore size were measured by adsorption–desorption
[13,23]
around ship’.
MIL‐101(Cr) is a frequently used
scaffold material due to its very large pore size and
[31,35–40]
effective surface area with large pore windows.
of N gas at 77.360 K using a Micrometrics ASAP 2000
2
In spite of the fact that the direct impregnation of
POM species into the large pores of MIL‐101(Cr) has been
attempted before, there are two main issues associated
with this approach: (a) the dispersion of the active species
is suboptimal as the large cavities of MIL‐101(Cr) are
filled with POM and the smaller ones remain vacant;
and (b) substantial leaching has been observed as the
immobilization is based on the adsorption equilibrium.
Thus successful POM encapsulation requires a one‐pot
instrument. Fourier transform infrared (FT‐IR) spectra
−
1
were obtained in the range 400–4000 cm using a JASCO
6300D instrument. Diffuse reflectance spectra were
recorded with a JASCO V‐670 UV–visible spectrophotom-
eter. The particle size and microscopic morphological
features of samples were imaged with a Sigma‐Zeiss
‘
build bottle around ship’ synthesis that has been demon-
[41]
strated previously.
Epoxides have attracted substantial attention as
building blocks in organic synthesis and synthesis
SCHEME
Co‐POM@MIL‐101
1
Methanolysis of epoxides catalysed by

MARANDI ET AL.
3 of 10
field‐emission scanning electron microscopy (SEM)
instrument. Transmission electron microscopy (TEM)
with an FEI Tecnai‐20 microscope was applied to charac-
terize crystal morphology and size of the new catalyst as
well as the dispersion of the POM. Finally the progress of
the reactions was monitored using GC analysis with an
Agilent GC6890 equipped with a 19096C006 80/100
WHP packed column and a flame ionization detector.
2.5 | Catalyst recovery and reuse
In order to investigate the recyclability and reusability of
the catalyst, it was filtered from the reaction medium
and washed with water, ethanol and acetone. The
reusability of the Co‐POM@MIL‐101 catalyst was investi-
gated repeatedly in methanolysis of styrene epoxide as
explained above. The catalyst was recovered from the
reaction medium by filtration at the end of each cycle,
then washed, activated and reused for four cycles with a
negligible catalyst leaching and a slight decrease of its
activity. The amount of POM leached after first run in
the filtrates was determined using ICP‐OES. The
structural stability of the catalyst was investigated using
XRD. The catalytic activity of this hybrid material was
compared with that of previously reported catalytic
systems.
2.2 | Synthesis of HF‐free MIL‐101
MIL‐101 samples were synthesized hydrothermally
according to a formerly reported method by Bromberg
[38]
et al.
in the absence of HF. In this method,
Cr(NO ) ⋅9H O (2.0 g, 5 mmol), terephthalic acid (0.83 g,
3
3
2
5
mmol) and deionized water (20 ml) were mixed, and
then the mixture was put in a Teflon‐lined hydrothermal
synthesis autoclave reactor and kept in an oven at 218 °C
for 18 h without stirring. After the synthesis and cooling
to room temperature, green raw product was separated
by centrifugation and washed with water, methanol and
acetone, and then dried and activated overnight under
vacuum.
3
| RESULTS AND DISCUSSION
3
1
.1 | Characterization of co‐POM@MIL‐
01 catalyst
The XRD patterns of MIL‐101 and the synthesized
catalyst, Co‐POM@MIL‐101, are shown in Figure 1. There
are similarities between the simulated results presented in
previous literature and the pattern of the synthesized
MIL‐101 which indicates structural confirmation of the
MOF.
of the isostructural catalyst are reduced somewhat
compared to pure MIL‐101 which can be related to the
encapsulated POM, but the crystal structure remains.
The Co‐POM peaks in the XRD pattern are weak, which
can be attributed to the deficiency of large Co‐POM
2.3 | Synthesis of co‐POM@MIL‐101
This composite material was prepared by mixing the
MIL‐101 precursor and the synthesized Co‐POM and
[31,53,54]
As shown in Figure 1, the peak intensities
water in an autoclave. In
a
typical procedure,
Cr(NO ) ⋅9H O (2.0 g, 5 mmol), terephthalic acid (0.83 g,
3
3
2
5
mmol), Co‐POM (in different amounts of 2.0, 1.6, 0.8
and 0.4 g) and deionized water (20 ml) were mixed and
sonicated for a short time resulting in a dark blue coloured
mixture. The suspension was put in a Teflon‐lined hydro-
thermal synthesis autoclave reactor and kept in an oven
at 218 °C for 18 h without stirring. The resulting Co‐
POM@MIL‐101 solid was separated by centrifugation
and washed with water, methanol and acetone, and then
activated under vacuum until fixed weight.
[55]
crystals on the exterior surface of MIL‐101.
2.4 | Catalytic reaction
Methanolysis reactions of various epoxides such as sty-
rene oxide, 2‐(phenoxymethyl)oxirane and 2‐[(allyloxy)
methyl]oxirane were performed a 25 ml round‐bottomed
flask at room temperature to afford the corresponding
alcohols in excellent yields in the presence of the
Co‐POM@MIL‐101 heterogeneous catalyst. The required
amount of Co‐POM@MIL‐101 was added to a solution
of 1 mmol of epoxide in 5 ml of methanol. The mixture
was stirred for 30 min at room temperature. The progress
of the reaction was monitored by GC.
FIGURE 1 XRD patterns of (a) Co‐POM, (b) MIL‐101, (c)
Co‐POM@MIL‐101 and (d) recovered catalyst after four cycles

4
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MARANDI ET AL.
TEM and SEM images of the Co‐POM@MIL‐101
hybrid material are shown in Figure 2. These images
of the cobalt cation is observed at ca 512 nm. It is noted
that d–d charge‐transfer transition of cobalt cation in
Co‐POM is shifted from 512 to 562 nm; this red shift can
be ascribed to the strong coordination interaction
between the cobalt cation and oxygen atoms in the POM
reveal micrometre‐sized crystallites with sizes and shapes
[23,56,57]
similar to those previously reported.
Spherical
interior particles illustrate incorporation of Co‐POM into
the MOF pores. Also, the energy‐dispersive X‐ray (EDX)
results, obtained from SEM analysis of the catalyst in
Figure 3(a), clearly show the presence of Co and W from
the POM and Cr related to MIL‐101(Cr). Furthermore,
the elemental mapping analysis indicates a good distribu-
tion of Co‐POM into the pores of MIL‐101(Cr) (Figure 3b).
Figure 4 shows the UV–visible spectrum of MIL‐101
containing Co‐POM in comparison with those of bare
MIL‐101 and Co‐POM. The absorption band at 255 nm
corresponds to oxygen–tungsten charge transfer assigned
[
58]
structure.
Although the intensities are weaker, these
peaks are also observed in the spectrum of Co‐
POM@MIL‐101. Also, the UV–visible spectra provide fur-
ther evidence of the intact MIL‐101 structure. The diffuse
reflectance spectrum of the encapsulated POM parallels
the spectrum of the free homogeneous POM species.
The intact structure of the POM in the composite
material was also confirmed using FT‐IR vibrational
spectroscopy. As shown in Figure 5(b), the FT‐IR spec-
trum of Co‐POM@MIL‐101 is the sum of the characteris-
tic bands of the free components: Co‐POM (Figure 5a)
[23]
to Keggin anions.
The d–d charge‐transfer transition
−
1
with characteristic peaks in the region 700–1200 cm
assigned to W═O, W―O―W and Co―O bonds
[
59,60]
and MIL‐101 (Figure 5c) with characteristic vibrational
bands of (O―C―O) groups of the framework around
−
1
1
1
550 and 1400 cm and of C═O vibrations at 1708 and
658 cm .
−
1 [61]
Nitrogen physisorption analysis (Figure 6) was used to
verify the constant porosity of Co‐POM@MIL‐101. The
strong uptake at a low relative pressure in N adsorp-
2
tion–desorption isotherms is the typical characteristic of
[
51]
a microporous material.
The quantity of gas absorbed
during Brunauer–Emmett–Teller (BET) nitrogen absorp-
tion isothermal analysis (Table 1) demonstrated that the
pore volume of Co‐POM@MIL‐101 was three times
smaller than that of bare MIL‐101 that is consistent with
loading of Co‐POM into the pores of MIL‐101, however
still sufficient for reagent diffusion in a catalysis applica-
tion. The BET surface area shows a predictable decrease
2
−1
from 2730 to 988 m g .
3.2 | Catalytic performance
Most of the ring‐opening reactions of epoxides under
acidic conditions lead to a combination of regioisomers,
and polymerization has been observed. One of the
reported catalysts for the ring‐opening reactions of
epoxides by various nucleophiles is a one‐electron transfer
[
62–65]
catalyst.
We have previously introduced Co‐POM as
a benign and highly efficient catalyst for alcoholysis of
[
66];
epoxides
here in the Co‐POM@MIL‐101 catalyst,
POMs are the active centres and MIL‐101 material is the
support, which provides high surface area and mesopo-
rous cages to encapsulate POMs.
We suggest that selective ring opening of various
epoxides with methanol proceeds through an electron
transfer mechanism. In previous work we have shown
that addition of a small amount of acrylonitrile to the
FIGURE 2 (a) SEM image and (b) TEM image of Co‐POM@MIL‐
01
1

MARANDI ET AL.
5 of 10
FIGURE 3 (a) SEM‐EDX analysis and
(
b) mapping of the hybrid Co‐POM@MIL‐
01 material (Au is from the sample
holder)
1

6
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MARANDI ET AL.
FIGURE 6
N
2
adsorption‐desorption isotherm of Co‐POM@MIL‐
101 (open symbols, adsorption; filled symbols, desorption)
FIGURE 4 UV–visible spectra of (a) Co‐POM, (b) MIL‐101 and
c) Co‐POM@MIL‐101
was demonstrated to be a well‐defined outer‐sphere elec-
(
[
67,68]
tron‐transfer agent in organic chemistry.
Since in
the complex the empty orbitals of cobalt have lost the
ability to interact directly with epoxides due to their
complete coverage with 12 inactive WO ligands, only
6
outer‐sphere electron transfer is possible. First, the
electrons are transferred from the oxygen atoms of the
epoxides to the inactive WO ligands, and then added to
6
the buried cobalt orbital. The result of this transformation
is a cation radical intermediate that is easily attacked by
the alcohols leading to epoxide ring opening.
The amount of initial POM during encapsulation in
MIL‐101 is a crucial factor in this reaction; therefore, the
effect of the initial amount of POM was investigated in
the synthesis of the catalyst. Co‐POM@MIL‐101 was syn-
thesized using 0.4, 0.8, 1.6 or 2.0 g of Co‐POM, 2.0 g of
CrNO and 0.83 g of terephthalic acid as initial precursors
3
for the synthesis of MIL‐101, and then the catalytic perfor-
mance of these hybrid materials was evaluated in the
methanolysis of styrene epoxide. When Co‐POM@MIL‐
101 with 0.4 g of POM was used, the conversion reached
90% within 30 min; in the case of 0.8 g of POM, the con-
version reached 100% in the same time. It is noteworthy
that, when using 1.6 and 2.0 g of POM, a significant
decrease was observed in the conversion (Table 2). This
is believed to be because of the total filling of the pore
volume therefore hampering the mass transfer of the
reactants to the active species. The catalytic activity of
pure MIL‐101 was also investigated in the model reaction
and, while it was not entirely inactive, only 20% of the
desired product was produced. Hence, Co‐POM@MIL‐
101 synthesized with 0.8 g of POM was chosen as the
appropriate catalyst. The amount of POM loading was
FIGURE 5 FT‐IR spectra of (a) Co‐POM, (b) Co‐POM@MIL‐101
and (c) MIL‐
1
01
reaction mixture as radical scavenger leads to a large
decrease in the reaction rates, consistent with an electron
[66]
5−
transfer mechanism. In previous studies, [CoW O ]
1
2 40

MARANDI ET AL.
7 of 10
TABLE 1 Specific surface area and total pore volume of MIL‐101 and the prepared catalyst
2
−1
3
−1
Sample
BET surface area (m g
)
Average pore diameter (nm)
Total volume (cm g )
MIL‐101
2730
988
3.6
1.35
Co‐POM@MIL‐101
2.0
0.5
TABLE 2 Effect of initial POM amount on the catalytic activity of
co‐POM@MIL‐101 catalyst in methanolysis of styrene epoxide
determined using ICP‐OES analysis based on the amount
of cobalt which showed a value of ca 0.0084 mmol g .
a
−1
b
The amount of Co‐POM@MIL‐101 catalyst per
volume of reaction mixture was also optimized. As shown
in Figure 7, when 50 mg of catalyst was employed, the
yield reached 45% within 30 min. As the amount of
catalyst increased to 150 mg, the yield reached 100%
within 30 min. However, using a greater amount of
catalyst, the time required to achieve 100% efficiency did
not reduce. Hence, 150 mg was chosen as the optimized
amount of catalyst in this reaction. As a negative control,
no product was observed in the absence of the catalyst
after 30 min.
Entry
Co‐POM (g)
Time (min)
Yield (%)
1
0
30
20
2
3
4
5
0.4
0.8
1.6
2
30
30
30
30
90
100
70
40
a
Reaction conditions: epoxide (1 mmol), MeOH (5 ml), catalyst (150 mg),
room temperature.
b
GC yield based on epoxide.
FIGURE 7 Optimization of catalyst amount. Reaction conditions:
styrene epoxide (1 mmol), MeOH (5 ml), Co‐POM@MIL‐101, room
temperature
FIGURE 8 Recycling of Co‐POM@MIL‐101 in the methanolysis
of styrene epoxide, reaction conditions: styrene epoxide (1 mmol),
MeOH (5 ml), Co‐POM@MIL‐101 (150 mg), room temperature
a
TABLE 3 Methanolysis of various epoxides catalysed by co‐POM@MIL‐101
b
−1
Entry
Epoxide
Time (min)
Product
Selectivity (%)
Yield (%)
TOF (h )
1
30
100
100
1504
2
3
30
30
100
100
96
88
1443
1323
a
Reaction conditions: epoxide (1 mmol), MeOH (5 ml), catalyst (150 mg), room temperature.
b
GC yield based on epoxide.

8
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MARANDI ET AL.
TABLE 4 Comparison of catalytic performance of co‐POM@MIL‐101 and reported MOF‐based catalysts for methanolysis of styrene oxide
−
1
Entry
Catalyst
Temperature (°C)
Time (min)
Yield (%)
Reusability (runs)
TOF (h
)
Ref.
[
[
[
[
[
50]
51]
69]
70]
49]
1
MIL‐101‐SO
3
H
RT
30
99
5
99
2
3
4
5
6
MIL‐101(HPW)
Cu‐MOF
40
20
99.8
93
3
98.5
5.3
RT
40
120
150
60
4
HKUST‐1
90
No data
5.6
[Fe (BTC)]
40
93
3
4
9.3
Co‐POM@MIL‐101
RT
30
100
1504
Present work
Under the optimized reaction conditions, allyl glycidyl
ether and phenyl glycidyl ether were subjected to
methanolysis in the presence of Co‐POM@MIL‐101. The
results show that these two linear epoxides were success-
fully converted to their corresponding β‐methoxy alcohols
in excellent yields (Table 3). While the TOF for homoge-
activated catalyst were stirred under reaction conditions
for 1 h; then the catalyst was separated by filtration and
the other reactant (epoxide) was added to the reaction
vessel and the reaction mixture was stirred again. No
noticeable conversion was obtained in the reaction when
following this sequence which confirms the heteroge-
neous nature of the catalyst.
For demonstration of the efficiency of the present
catalyst and to complete our work, the catalytic perfor-
mance of this catalyst was compared with that of some
MOF‐based catalysts reported previously in the litera-
ture. The results, which are summarized in Table 4,
show that this catalyst is preferable in respect of
reaction temperature and conversion time and mostly
in TOF.
−
1 [66]
neous catalyst, Co‐POM, was about 80 h ,
the TOF
−
1
reached ca 1500 h
for Co‐POM@MIL‐101. The
singular catalytic activity of the heterogeneous catalyst
can be ascribed to trapping of the catalytic active sites
(Co‐POM) within the MOF pores.
3.3 | Catalyst reuse and stability
One of the important factors for a solid catalyst system is
the stability of the active component under reaction
process with regard to maintaining structural integrity
and leaching of the catalyst. To study the stability and
reusability of the active Co‐POM component in the Co‐
POM@MIL‐101 catalyst, a four‐cycle series of experi-
ments was performed using methanolysis of styrene
epoxide as a model reaction (Figure 8). To prevent the
reduction of catalyst performance, the catalyst was
washed with water, ethanol and acetone to remove
trapped reactants after each cycle and activated under
vacuum at 100 °C overnight. The amount of Co‐POM
remaining in the catalyst was determined using ICP‐
OES analysis. Approximately 0.01 wt% Co‐POM leached
from the catalyst after one run. The XRD pattern of the
Co‐POM@MIL‐101 catalyst after four cycles of the
methanolysis of styrene epoxide still showed the charac-
teristic peaks of Co‐POM@MIL‐101 (Figure 1d). Thus
the structural integrity of Co‐POM@MIL‐101 is main-
tained during the four reaction cycles.
4 | CONCLUSIONS
We report the successful synthesis of a new hybrid catalyst
by encapsulation of Co‐POM into MIL‐101 synthesized in
a one‐pot process. The catalytic activity of this heteroge-
neous catalyst was investigated in the methanolysis of
epoxides. The results indicated that the TOF value of Co‐
POM@MIL‐101 was more than 20 times higher than that
of homogeneous Co‐POM catalyst. Easy preparation,
reusability and incredibly benign reaction conditions are
other important factors that make Co‐POM@MIL‐101 an
efficient and unique immobilized catalyst.
ACKNOWLEDGEMENT
We are grateful to the Research Council of the University
of Isfahan for financial support of this work.
In order to investigate the nature of the catalyst
homogeneous versus heterogeneous) in the studied
ORCID
(
reaction, two paths were followed. In the first one, solid
catalyst was removed from the reaction media after
Shahram Tangestaninejad
5263-9795
http://orcid.org/0000-0001-
1
0 min of reaction and reaction progress was followed
Majid Moghadam http://orcid.org/0000-0001-8984-1225
by GC. No further conversion was observed. In the other
pathway, one of the reactants (methanol) and the
Iraj Mohammadpoor‐Baltork
7998-5401
http://orcid.org/0000-0001-

MARANDI ET AL.
9 of 10
REFERENCES
[26] S. S. Balula, I. C. Santos, L. Cunha‐Silva, A. P. Carvalho, J.
Pires, C. Freire, J. A. Cavaleiro, B. de Castro, A. M. Cavaleiro,
Catal. Today 2013, 203, 95.
[
1] B. Chen, C. Liang, J. Yang, D. S. Contreras, Y. L. Clancy, E. B.
Lobkovsky, O. M. Yaghi, S. Dai, Angew. Chem. 2006, 118, 1418.
[
[
[
27] Y. Yang, Y. Guo, C. Hu, Y. Wang, E. Wang, Appl. Catal. A 2004,
73, 201.
28] O. Kholdeeva, N. Maksimchuk, G. Maksimov, Catal. Today
010, 157, 107.
[
[
2] S. Li, F. Huo, Nanoscale 2015, 7, 7482.
2
3] D. M. D'Alessandro, B. Smit, J. R. Long, Angew. Chem. Int. Ed.
2
010, 49, 6058.
2
[
[
[
[
4] J.‐R. Li, J. Yu, W. Lu, L.‐B. Sun, J. Sculley, P. B. Balbuena, H.‐C.
29] B. Watson, M. Barteau, L. Haggerty, A. Lenhoff, R. Weber,
Zhou, Nat. Commun. 2013, 4, 1538.
Langmuir 1992, 8, 1145.
5] Z. Hu, Z. Kang, Y. Qian, Y. Peng, X. Wang, C. Chi, D. Zhao, Ind.
Eng. Chem. Res. 2016, 55, 7933.
[
[
30] R. R. Ozer, J. L. Ferry, J. Phys. Chem. B 2002, 106, 4336.
31] G. Férey, C. Mellot‐Draznieks, C. Serre, F. Millange, J. Dutour,
S. Surblé, I. Margiolaki, Science 2005, 309, 2040.
6] L. E. Kreno, K. Leong, O. K. Farha, M. Allendorf, R. P. Van
Duyne, J. T. Hupp, Chem. Rev. 2011, 112, 1105.
[32] N. Maksimchuk, M. Timofeeva, M. Melgunov, A. Shmakov, Y.
7] P. Horcajada, T. Chalati, C. Serre, B. Gillet, C. Sebrie, T. Baati, J.
F. Eubank, D. Heurtaux, P. Clayette, C. Kreuz, Nat. Mater.
A. Chesalov, D. Dybtsev, V. Fedin, O. Kholdeeva, J. Catal. 2008,
257, 315.
2
010, 9, 172.
[
[
33] N. V. Maksimchuk, O. A. Kholdeeva, K. A. Kovalenko, V. P.
[
[
8] R. Ricco, L. Malfatti, M. Takahashi, A. J. Hill, P. Falcaro,
J. Mater. Chem. A 2013, 1, 13033.
Fedin, Isr. J. Chem. 2011, 51, 281.
34] S. Ribeiro, C. M. Granadeiro, P. Silva, F. A. A. Paz, F. F. De
9] R. J. Kuppler, D. J. Timmons, Q.‐R. Fang, J.‐R. Li, T. A. Makal,
M. D. Young, D. Yuan, D. Zhao, W. Zhuang, H.‐C. Zhou, Coord.
Chem. Rev. 2009, 253, 3042.
Biani, L. Cunha‐Silva, S. S. Balula, Catal. Sci. Technol. 2013,
3
, 2404.
[35] S. Wang, L. Bromberg, H. Schreuder‐Gibson, T. A. Hatton, ACS
[
[
[
10] L. Ma, C. Abney, W. Lin, Chem. Soc. Rev. 2009, 38, 1248.
11] M. Yoon, R. Srirambalaji, K. Kim, Chem. Rev. 2011, 112, 1196.
12] A. Dhakshinamoorthy, H. Garcia, Chem. Soc. Rev. 2012, 41,
Appl. Mater. Interfaces 2013, 5, 1269.
[36] H. Li, Z. Zhu, F. Zhang, S. Xie, H. Li, P. Li, X. Zhou, ACS Catal.
011, 1, 1604.
2
5
262.
13] J. Juan‐Alcañiz, J. Gascon, F. Kapteijn, J. Mater. Chem. 2012,
2, 10102.
[37] P. Serra‐Crespo, E. V. Ramos‐Fernandez, J. Gascon, F. Kapteijn,
Chem. Mater. 2011, 23, 2565.
[
[
[
[
[
2
[38] L. Bromberg, Y. Diao, H. Wu, S. A. Speakman, T. A. Hatton,
Chem. Mater. 2012, 24, 1664.
14] M.‐H. Sun, S.‐Z. Huang, L.‐H. Chen, Y. Li, X.‐Y. Yang, Z.‐Y.
Yuan, B.‐L. Su, Chem. Soc. Rev. 2016, 45, 3479.
[39] Z. Saedi, S. Tangestaninejad, M. Moghadam, V. Mirkhani, I.
Mohammadpoor‐Baltork, J. Coord. Chem. 2012, 65, 463.
15] J. M. Clemente‐Juan, E. Coronado, A. Gaita‐Ariño, Chem. Soc.
Rev. 2012, 41, 7464.
[40] F. Zadehahmadi, S. Tangestaninejad, M. Moghadam, V.
Mirkhani, I. Mohammadpoor‐Baltork, R. Kardanpour, Appl.
Organomet. Chem. 2015, 4, 209.
16] P. Koegerler, B. Tsukerblat, A. Mueller, Dalton Trans. 2010,
3
9, 21.
[
41] L. Yang, H. Naruke, T. Yamase, Inorg. Chem. Commun. 2003,
17] K. D. D. Gunaratne, G. E. Johnson, A. Andersen, D. Du, W.
6
, 1020.
Zhang, V. Prabhakaran, Y. Lin, J. Laskin, J. Phys. Chem. C
2
014, 118, 27611.
[42] C. Bonini, G. Righi, Synthesis 1994, 225.
[
18] H. Lv, Y. V. Geletii, C. Zhao, J. W. Vickers, G. Zhu, Z. Luo, J.
[43] N. Iranpoor, I. M. Baltork, Synth. Commun. 1990, 20, 2789.
Song, T. Lian, D. G. Musaev, C. L. Hill, Chem. Soc. Rev. 2012,
[
[
[
44] M. Shimizu, A. Yoshida, T. Fujisawa, Synlett 1992, 204.
4
1, 7572.
45] A. Rao, S. Paknikar, J. G. Kirtane, Tetrahedron 1983, 39, 2323.
[
[
[
[
[
19] M. Vazylyev, D. Sloboda‐Rozner, A. Haimov, G. Maayan, R.
46] M. Mirza‐Aghayan, M. Alizadeh, M. M. Tavana, R.
Boukherroub, Tetrahedron Lett. 2014, 55, 6694.
Neumann, Top. Catal. 2005, 34, 93.
20] W. Guo, H. Lv, J. Bacsa, Y. Gao, J. S. Lee, C. L. Hill, Inorg.
Chem. 2016, 55, 461.
[
47] D. Barreca, M. P. Copley, A. E. Graham, J. D. Holmes, M. A.
Morris, R. Seraglia, T. R. Spalding, E. Tondello, Appl. Catal. A
2006, 304, 14.
21] W. Zhu, P. Wu, Y. Chao, H. Li, F. Zou, S. Xun, F. Zhu, Z. Zhao,
Ind. Eng. Chem. Res. 2013, 52, 17399.
[
[
[
48] R. F. Mendes, P. Silva, M. M. Antunes, A. A. Valente, F. A. A.
22] J. Gascon, U. Aktay, M. D. Hernandez‐Alonso, G. P. van Klink,
F. Kapteijn, J. Catal. 2009, 261, 75.
Paz, Chem. Commun. 2015, 51, 10807.
49] A. Dhakshinamoorthy, M. Alvaro, H. Garcia, Chem. – Eur. J.
2010, 16, 8530.
23] J. Juan‐Alcañiz, E. V. Ramos‐Fernandez, U. Lafont, J. Gascon,
F. Kapteijn, J. Catal. 2010, 269, 229.
50] Y. X. Zhou, Y. Z. Chen, Y. Hu, G. Huang, S. H. Yu, H. L. Jiang,
[
[
24] Y. Guo, C. Hu, J. Mol. Catal. A 2007, 262, 136.
Chem. – Eur. J. 2014, 20, 14976.
25] R. Villanneau, A. Marzouk, Y. Wang, A. B. Djamaa, G. Laugel,
[51] L. H. Wee, F. Bonino, C. Lamberti, S. Bordiga, J. A. Martens,
A. Proust, F. Launay, Inorg. Chem. 2013, 52, 2958.
Green Chem. 2014, 16, 1351.

10 of 10
MARANDI ET AL.
[
[
[
52] M. H. Habibi, S. Tangestaninejad, I. Mohammadpoor‐Baltork,
V. Mirkhani, B. Yadollahi, Tetrahedron Lett. 2001, 42, 6771.
[64] D. L. Fox, A. A. Robinson, J. B. Frank, R. N. Salvatore, Tetrahe-
dron Lett. 2003, 44, 7579.
53] Y. Huang, S. Liu, Z. Lin, W. Li, X. Li, R. Cao, J. Catal. 2012,
[65] M. Chini, P. Crotti, L. Favero, F. Macchia, M. Pineschi, Tetrahe-
dron Lett. 1994, 35, 433.
2
92, 111.
54] D. Y. Hong, Y. K. Hwang, C. Serre, G. Ferey, J. S. Chang, Adv.
Funct. Mater. 2009, 19, 1537.
[66] S. Tangestaninejad, M. Moghadam, V. Mirkhani, B. Yadollahi,
S. M. R. Mirmohammadi, Monatsh. Chem. 2006, 137, 235.
[
[
55] X. Yang, L. Qiao, W. Dai, Chin. J. Catal. 2015, 36, 1875.
[67] A. Weinstock, Chem. Rev. 1998, 98, 113.
56] S. K. Abd El Rahman, H. M. Hassan, M. S. El‐Shall, Appl. Catal.
A 2014, 487, 110.
[68] L. Eberson, J. Am. Chem. Soc. 1983, 105, 3192.
[69] D. Jiang, T. Mallat, F. Krumeich, A. Baiker, J. Catal. 2008,
[
57] M. Saikia, D. Bhuyan, L. Saikia, Appl. Catal. A 2015, 505, 501.
257, 390.
[
58] W. Wu, T. Teng, X.‐Y. Wu, X. Dui, L. Zhang, J. Xiong, L. Wu,
C.‐Z. Lu, Catal. Commun. 2015, 64, 44.
[70] L. H. Wee, M. R. Lohe, N. Janssens, S. Kaskel, J. A. Martens,
J. Mater. Chem. 2012, 22, 13742.
[
[
[
59] E. Rafiee, M. Khodayari, M. Kahrizi, R. Tayebee, J. Mol. Catal.
A 2012, 358, 121.
How to cite this article: Marandi A,
Tangestaninejad S, Moghadam M, et al.
Dodecatungstocobaltate heteropolyanion
encapsulation into MIL‐101(Cr) metal–organic
framework scaffold provides a highly efficient
heterogeneous catalyst for methanolysis of
epoxides. Appl Organometal Chem. 2017;e4065.
https://doi.org/10.1002/aoc.4065
60] Y. Ding, B. Ma, Q. Gao, G. Li, L. Yan, J. Suo, J. Mol. Catal. A
2
005, 230, 121.
61] F. Zadehahmadi, S. Tangestaninejad, M. Moghadam, V.
Mirkhani, I. Mohammadpoor‐Baltork, A. R. Khosropour, R.
Kardanpour, Appl. Catal. A 2014, 477, 34.
[
62] N. Iranpoor, M. Shekarriz, F. Shiriny, Synth. Commun. 1998,
2
8, 347.
[
63] S. Mohammadpoor‐Baltork, H. Tangestaninejad, V. Aliyan,
Synth. Commun. 2000, 30, 2365.