Multifunctional Polymolybdate-Based Metal-Organic Framework as an Efficient Catalyst for the CO2 Cycloaddition and as the Anode of a Lithium-Ion Battery

Article abstract of DOI:10.1021/acs.inorgchem.9b01977

A three-dimensional polymolybdate-based metal-organic framework (POMOF) consisting of Zn-?-Keggin unit and organic linker, {[PMo₈^VMo₄^VIO₃₇(OH)₃Zn₄][BPE]₂}·[BPE] (1), w

Full text of DOI:10.1021/acs.inorgchem.9b01977

Article
pubs.acs.org/IC
Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
Multifunctional Polymolybdate-Based Metal−Organic Framework as
an Efficient Catalyst for the CO2 Cycloaddition and as the Anode of a
Lithium-Ion Battery
Yun-Shan Xue,†,‡,# Wei-Wei Cheng,†,# Xi-Ming Luo,† Jia-Peng Cao,† and Yan Xu*,†
†College of Chemical Engineering, State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University,
Nanjing 210009, P. R. China
‡School of Chemistry and Environmental Engineering, Yancheng Teachers University, Yancheng, Jiangsu 224002, P. R. China
S
* Supporting Information
ABSTRACT: A three-dimensional polymolybdate-based metal−organic
framework (POMOF) consisting of Zn-ε-Keggin unit and organic linker,
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{[PMo8 Mo4 O37(OH)3Zn4][BPE]2}·[BPE] (1), was successfully obtained
by the hydrothermal method. Compound 1 is composed of Zn-ε-Keggin units
and BPE ligands, featuring a fascinating 5-fold interpenetrating framework with
dia topology. The catalytic performance of compound 1 was investigated, and
experiments showed that 1 could effectively facilitate the cycloaddition
reaction of CO2 with epoxides as Lewis acid heterogeneous catalyst. Moreover,
compound 1 also was studied as LIBs anode material, and it showed reversible
capacity of 546 mA h g−1 at 100th cycle.
framework. In contrast to above-mentioned heterogeneous
INTRODUCTION
■
catalysts, POMOFs exhibit efficient catalytic activity owing to
their unique modular nature and facile tunability (i.e., high
surface area, regular and tunable cavities, high catalytically
active site density, and strong Brønsted acidity), which make
them as ideal heterogeneous catalysts distinctively different
from MOFs and POMs.40−48 Ma et al. synthesized a novel
POMOF based on polyoxovanadate, in conjunction with Lewis
acid sites, which showed good catalytic activity and high
selectivity in the CO2 cycloaddition reaction.44 Xu et al.
reported a scarce 3D POM-based polymer bridged by CO2,
which also exhibited remarkable catalytic behavior for the
cycloaddition of CO2 with epoxides.45
Currently, the exploitation of energy storage materials is
gradually becoming a research hotspot.49−55 With high energy
density and light weight, lithium-ion batteries show great
application prospects in the area of energy storage.56−61 Many
efforts have been devoted to exploiting anode electrode
materials with superior performance. Previous studies reveal
that POMs have potential as LIBs electrode materials because
of their multielectron-transfer character.62−66 As a special class
of POM family, POMOFs have received the widespread
attention, which incorporate the POM anions into the MOFs
framework and combine their virtues.67−74 Some research
shows that the open-framework of MOFs could effectively
strengthen the cycling stability and overcome the shortcomings
Recently, carbon dioxide (CO2) chemistry has drawn much
attention and became a hot research topic, not only because
CO2 brings about adverse consequence on global warming and
climate change as the primary greenhouse gas but also because
CO2 is naturally abundant, innoxious, cheap, and an important
C1 resource.1−7 Therefore, many efforts have been made to
fixation and transformation CO2 into valuable organic
products, e.g., poly(carbonates), carboxylic acids, carbonates,
and carbamate derivatives.8−11 Among various CO2 conversion
reactions, the cycloaddition of CO2 with epoxides is one of the
most popular green routes. The reaction products (cyclic
carbonates) are important chemical precursors, which have
widespread availability in the fields of fine chemicals and
pharmaceuticals industry.12−17 In particular, inexhaustible CO2
resource has been converted to value-added products with no
byproducts, which is a perfect 100% atom economical
technical route.18,19 Thus far, various homogeneous catalysts,
e.g., ionic liquids, metal complexes, and quaternary ammonium
salts, have been well studied in the cycloaddition of carbon
dioxide.20−24 Nevertheless, the application of these homoge-
neous catalysts are limited by their inherent characteristics,
which are difficult to separate from the products and
recycle.25−30 To overcome these defects, heterogeneous
catalysts, e.g., zeolites, metal oxide, and metal−organic
frameworks, have been extensively developed.31−39 In this
field, POMOFs have attracted ever-growing research interest as
promising heterogeneous candidate catalysts, providing a new
approach for incorporating catalytically active sites in porous
Received: July 4, 2019
© XXXX American Chemical Society
A
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of large volume change during insertion/extraction of Li+
process.75−77 Thus, it is significative to explore POMOFs
materials utilized as LIBs anode materials. Here, a three-
dimensional (3D) interpenetrated network with dia topology,
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namely, {[PMo8 Mo4 O37(OH)3Zn4][BPE]2}·[BPE] (1), was
constructed based on tetrahedral Zn-ε-Keggin unit and trans-
1,2-bis(4-pyridyl)ethylene ligand (BPE). In the initial cycle,
compound 1 exhibits desirable discharge capacity of 881 mA h
g−1 and also shows good cycling stability at 100th cycle (546
mA h g−1). Additionally, compound 1 displays good catalytic
activity and efficiently promotes cycloaddition reaction of CO2
with epoxides as Lewis-acid catalyst, due to the open Mo sites
in the channels. Remarkably, compound 1 could be reused
after recycling five times, and the yield saw no obvious
decrease.
Figure 2. (a) Single adamantanoid cage; (b) three-dimensional
network packing of adamantanoid cages along b direction.
The cage possesses a maximum size of 59.3 × 38.9 Å, and
consists of 10 Zn4-ε-Keggin units and 12 BPE fragments. The
adjacent cages pack with one another to build the 3D open
framework of 1 (Figure 2b). Moreover, the single dia network
of compound 1 contains a 3D channel system, and the pore
size of channels are 44.4 × 27.5 Å, 27.5 × 44.4 Å, and 13.7 ×
13.7 Å, respectively, viewing along different directions (Figures
S1−S3). The channel of an individual net is large enough to
form a 5-fold interpenetration in 1 (Figure 3a), thus increasing
EXPERIMENTAL SECTION
■
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Synthesis of {[PMo8 Mo4 O37(OH)3Zn4][BPE]2}·[BPE] (1). Mo
powder (60 mg, 0.60 mmol), Na2MoO4·2H2O (847 mg, 3.5 mmol),
Zn(OAc)2·2H2O (219 mg, 1 mmol), H3PO3 (40 mg, 0.5 mmol), BPE
(109 mg, 0.60 mmol), 200 μL tetrapropylammonium hydroxide (40
wt %), and 9 mL deionized water were added to a beaker with stirring
for 1 h. Next, the pH value of mixture was adjusted to 4.2 by the
addition of 2 M HCl and stirred for a further 0.5 h. Subsequently, the
mixture was heated at 180 °C for 72 h, sealed in a Teflon reactor.
Black rod crystals of 1 were obtained in ca. 67.11% yield based on
BPE after the reaction had cooled to room temperature. Anal. Calcd
for C36H28Mo12N6O40PZn4: C, 16.42; N, 3.19; H, 1.26. Found: C,
16.66; N, 3.09; H, 1.20.
RESULTS AND DISCUSSION
■
Structure Description. Compound 1 crystallizes in the
I41/amd space group (tetragonal crystal system, No. 141). The
asymmetric unit consists of a half of a coordinated BPE ligand,
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one-quarter {ε-PMo8 Mo4 O37(OH)3Zn4} unit (Zn4-ε-Keg-
gin), and half of the guest BPE ligand. All Zn atoms capped on
the ε-Keggin unit are 4-coordinated through one nitrogen
atom of BPE ligand and three oxygen atoms of ε-Keggin unit in
a tetrahedral coordination geometry. The distances of Mo−Mo
are around 2.6 and 2.9 Å, suggesting the coexistence of
M o ( V I ) a n d M o ( V ) i o n s i n t h e { ε -
Figure 3. (a) Schematic view of 5-fold interpenetrated dia topology;
(b) view of the structure of compound 1 along the c direction.
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PMo8 Mo4 O37(OH)3Zn4} unit. It is noteworthy that Zn-ε-
Keggin unit is bound to four BPE ligands by four capped Zn
atoms on the POM surface (Figure 1) and lies on a 4-
coordinated 66 net, which links to neighboring Zn4-ε-Keggin
unit by BPE ligand, giving a 5-fold interpenetrated dia net.
The conspicuous structural characteristic is the existence of a
large adamantanoid cage in the single network (Figure 2a).
the stability of the framework. It is rarely found that the
interpenetration degree is up to five with dia net on the basis
of coordination bonds. When dia nets were interpenetrated,
the channels were almost completely blocked, while the
channels along c direction remain unchanged (Figure 3b).
PLATON program calculation shows that the accessible
solvent volume occupies 17.0% of total crystal volume. Of
particular note is that the value is 41.6% when all extra-
framework molecules are removed.
In this case, a porous 5-fold interpenetrated network of
diamond-like POMOF was constructed through the introduc-
tion of bidentate N-containing ligand BPE into the tetrahedral
Zn4-ε-Keggin system. Recently, several noteworthy studies
based on Zn4-ε-Keggin are published and there are three
examples of POMOF with dia topology. Lan et al. reported the
construction of NENU-506 and NENU-507, which exhibited
2-fold and 4-fold interpenetrated dia networks based on two
different bidentate ligands of isonicotinic acid and 4-(pyridin-
4-yl) benzoic acid, respectively.72 Su et al. also synthesized a
novel 8-fold [4 + 4] interpenetrating framework with dia
topology built from tetrahedral Zn4-ε-Keggin unit and
semirigid bidentate ligand (i.e., 4′-(4-carboxylatophenoxy)-
Figure 1. Views of the coordination environment of (a) the Zn4-ε-
Keggin unit and (b) BPE ligand.
B
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[1,1′-biphenyl]-4-carboxylate).78 These compounds all exhibit
excellent electrochemical performance.
Table 1. CO2 Cycloaddition with PO under Various
Reaction Conditions
a
TG and IR Analyses. The thermal stability of as-
synthesized sample was studied and thermogravimetric analysis
was performed at room temperature to 1000 °C (Figure S5).
The weight loss is 6.8% at about 25−370 °C, assigned to the
loss of free BPE ligands (calcd 6.9%). On further heating, the
coordinated BPE gradually decomposed and the structure
collapsed. As shown in Figure S6, the peaks at 1076 and 937
cm−1 are assigned to P−O and Mo−O vibrations of inorganic
skeleton of the POM, respectively. The band around 784 cm−1
is attributed to Mo−O−Mo vibration. The signatures of BPE
ligand could be found in the regions of 1660−1430 cm−1.
Catalytic Performance. As for many other reported
POMOFs, compound 1 possesses relatively high thermal and
chemical stabilities. The PXRD patterns showed that structure
of 1 remained intact, after the samples immersed in acidic or
alkaline solutions with different pH ranges 1−13 (Figure S4).
Moreover, thermogravimetric analyses (TGA) indicated that
the framework of 1 could be stabilized to 300 °C, and there
was no apparent weight loss(Figure S5). The single-crystal
structural analysis reveals that crystal structure of 1 contains
large 1D channels (13.7 × 13.7 Å) along the c direction.
PLATON program calculations indicate that the accessible
void volume is estimated as 41.6% of total volume (8990.3 Å3)
when the guest BPE ligands are omitted. Thus, we probed its
gas sorption properties. Before the tests, the freshly prepared
crystals were immersed in CH2Cl2 or solvents exchanging, with
CH2Cl2 refreshed every 6 h. Then the samples after solvent
exchange were put into SFT HPR-100 reactor with super-
critical carbon dioxide to further remove guest molecules in the
framework. The activated samples were highly vacuumed for 4
h and heated at 100 °C by using “degas” program of the
adsorption analyzer. After activation treatment (i.e., super-
critical carbon dioxide), compound 1 exhibited moderate N2
uptake at 77 K and the BET surface area was calculated as 395
m2/g (Figure S7). Moreover, the CO2 adsorption amount was
51 cm3/g at 273 K and 760 Torr (Figure S8).
Considering high density of accessible Mo centers, porosity,
as well as CO2 uptakes, compound 1 as catalyst was explored
to catalyze CO2 cycloaddition with epoxides. The catalytic
activity of 1 was investigated by using the reaction of propylene
oxide (PO) and CO2 as model reaction. Several factors were
examined to search optimal catalytic conditions. The
experimental results were presented in Table 1. In our initial
experiments, cycloaddition reaction was implemented in 25
mL stainless steel autoclave under mild conditions of 0.2 MPa
and 30 °C for 6 h with tetra-n-butyl-ammonium bromide (n-
Bu4NBr) as cocatalyst. The yield of PC was 16.0%,
demonstrating that compound 1 has an inefficient catalytic
behavior under these conditions (entry 1). The PO conversion
was improved as reaction time was prolonged (entries 2−3),
however, the yields are still low under those conditions. Thus,
the temperature was raised to 45 °C, the yield was improved to
36.3% after 6 h (entry 4). The activity of catalytic system was
improved remarkably, indicating that the energy barrier was
reduced with the temperature increased.79 Subsequently, CO2
pressure was increased from 0.2 to 0.5 MPa, and the PC yield
reached 88.6% for 6 h, keeping the temperature at 45 °C
(entry 5). The above results indicate that CO2 pressure and
reaction temperature have great impact on the yield of PC. As
shown in Figure 4a, at the beginning, the PO conversion
increased with the increasing of CO2 pressure in the range of
entry
temperature (°C)
pressure (MPa)
time (h)
yield (%)
1
2
3
4
5
6
30
30
30
45
45
45
45
45
45
0.2
0.2
0.2
0.2
0.5
0.5
0.5
0.5
0.5
6
12
24
6
16.0
29.1
37.1
36.3
88.6
>99
14.5
22.5
93.5
6
10
10
10
10
b
7
c
8
d
9
a
Reaction conditions: compound 1 (0.1 mol %, based on Zn4-ε-
Keggin unit), PO (20 mmol), n-Bu4NBr (0.5 mmol, 2.5 mol %) at
various conditions. The yield of PC was determined by H NMR
spectroscopy. No n-Bu4NBr in the reaction. No compound 1 in the
1
b
c
d
reaction. The yield of the fifth cycling.
0−0.5 MPa. The yield did not show substantial increase and
was approximately constant further increased CO2 pressure,
suggesting that 0.5 MPa was the optimal pressure in our
catalytic system. The kinetic studies showed that the substrate
(PO) was completely converted to the carbonates (the final
>99%) within 10 h (Figures 4b and S9, entry 6), which further
indicated the compound 1 was an effective heterogeneous
catalyst. In addition, no PC was formed without catalyst and
cocatalyst. When compound 1 or n-Bu4NBr was used solely as
the catalyst, the yields were low (entries 7−8) at 45 °C and 0.5
MPa for 10 h. Comparably, the PC yield was remarkably
improved when n-Bu4NBr and catalyst 1 were used
simultaneously to form a binary catalytic system. This
phenomenon is common in other catalytic systems for CO2
coupling with epoxides, which is attributed to synergistic effect
to impel the proceeding of CO2 cycloaddition reaction.80−82
Meanwhile, we found that the optimal amount of n-Bu4NBr as
cocatalyst is 0.5 mmol under the same conditions by control
experiments (Table S1, entries 1−4). When we used n-Bu4NCl
to replace n-Bu4NBr, the results showed that bromine salt
possessed better activity than chlorine salt (Table S1, entry 5).
The most likely cause of this condition is the better leaving
ability and nucleophilicity of Br− than Cl−.83 On bases of the
experimental results stated above, the optimal catalytic
conditions could be determined with 1 (0.1 mol %) and n-
Bu4NBr (2.5 mol %) as cocatalysts at 45 °C and 0.5 MPa for
10 h. Besides, we employed BPE ligand and Mo powder as
catalysts, respectively, and the yields of PC were 23.7% and
37.9% (Table S1, entries 6−7), which indicates the excellent
catalytic effect of compound 1 to active the epoxide. To
compare catalytic performance of this POMOF, we selected
MOFs with similar porous channels and did control experi-
ments under the optimal catalytic conditions (Table S1, entries
8−10). The result also shows compound 1 having high
catalytic activity to the CO2 cycloaddition reaction with PO.
Different types of epoxides were employed as substrates
under the optimal catalytic conditions in the following
reactions to check the catalytic generality of catalyst 1.
Experimental results were listed in Table 2. The small-sized
epoxide substrates of epichlorohydrin and 1,2-epoxybutane
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Figure 4. Influence of (a) CO2 pressure (T = 45 °C, t = 6 h) and (b) time (P(CO2) = 0.5 MPa, T = 45 °C) on the reaction.
a
Table 2. Cycloaddition of CO2 with Various Substrates
Scheme 1. Proposed Mechanism of CO2 Cycloaddition
Reaction Using 1 and n-Bu4NBr as Co-Catalysts
a
Reaction conditions: catalyst 1 (0.1 mol %), n-Bu4NBr (2.5 mol %),
intramolecular ring-closure reaction, where the oxygen atom
from alkylcarbonate salt (II) attacks the C−Br carbon to
release Br−, and n-Bu4NBr is simultaneously recycled. There-
fore, the synergistic effect plays an important role between
catalyst 1 and n-Bu4NBr as cocatalysts in facilitating CO2
coupling reaction with epoxide to form cyclic carbonates.
Electrochemical Performance. It is known that ε-
Keggin-type POMs usually exhibit excellent redox properties
and are considered as electron reservoirs.84 The open
framework structure of POMOF is favorable to the trans-
mission capacity of electrons in the electrolyte and electrons of
Li+ ions. Moreover, the structural characteristics of POMOF
have been proved to effectively increase the cycling stability
and improve the shortcomings of large volume change during
discharge−charge process, giving rise to excellent electro-
chemical performance. So, on the basis of the above analysis,
compound 1 was investigated as an anode material. A series of
electrochemical tests of charge and discharge cycling stability,
cyclic voltammetry (CV), rate capability (RC), constant
current charge, and discharge activity were carried out to
investigate electrochemical performance of compound 1 as
anode materials for LIBs. As seen from CV curves, irreversible
reduction peak can be observed at about 0.36 V in the first
circle, revealing that a solid electrolyte interphase film is
generated (Figure 5b). However, the corresponding oxidation
peaks are less pronounced. The phenomenon shows the
process is largely irreversible. In the following cycles, reversible
oxidative and reductive peaks were found at 1.47 and 1.2 V,
epoxides (20 mmol), CO2 (0.5 MPa), 10 h, 45 °C.
provided an almost complete conversion (Figures S10 and S11,
entries 2−3). The cycloaddition reaction of styrene oxide and
2-(phenoxymethyl) oxirane were catalyzed with high yield
(Figures S12 and S13, entries 4−5), which also demonstrated
effective catalytic performance of 1. As a heterogeneous
catalyst, stability and reusability are essential features to be
considered in industrial applications. PO was employed as
substrate to evaluate the cycling performance of 1 under the
optimized catalytic conditions. Compound 1 as catalyst is
separated from reaction mixture by filtration. After 5 runs, PC
yield slightly decreased (93.5%, Figure S14). PXRD of recycled
samples exhibited that the structural integrity of 1 remained
almost unchanged (Figure S15). The result demonstrates that
catalyst 1 shows good recyclable performance.
As shown in Scheme 1, in view of current catalytic results
and previous studies, a possible synergistic catalytic mechanism
is proposed about POMOFs-catalyzed CO2 cycloaddition.
First, Lewis acid Mo sites interacts with oxygen atom from
epoxide, resulting in the ring of epoxide activated. Then, Br−
ion attacks the less sterically hindered β-carbon atom of
activated epoxide, forming metal-coordinated bromoalkoxide
(I). Subsequently, CO2 further couples with ring-opened
epoxide to yield the alkylcarbonate salt (II). Finally,
intermediate II is transformed into cyclic carbonate by
D
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Figure 5. (a) CV of 1 with scan rate of 0.2 mV s−1 (0.01−3.0 V). (b) Long cycling performance of 1 (100 mA g−1). (c) Charge−discharge profiles
of 1 for the first, 10th, 50th and 100th cycles (100 mA g−1). (d) Rate capacity of compound 1.
respectively, owing to the redox process of Zn and Mo. In
addition, the second and third curves almost overlap, showing
good cycle stability of compound 1 as electrode. Cycling
performance of current density (100 mA g−1) and Coulombic
efficiency (CE) are presented in Figure 5b. It is seen that
reversible specific capacity is 546 mA h g−1 and CE reach
almost 100% at 100th cycle. Compound 1 has the
commendable cycling stability, which might be ascribed to
POMs as stable electron donors and 5-fold interpenetrated
framework structure (alleviating volume change of the POM
and averting POM structure from being damaged in charging
and discharging process). The charge−discharge profiles of the
selected cycles (first, 10th, 50th, 100th) are shown in Figure
5c. The first discharge capacity is 881.65 mA h g−1, while its
charge capacity is 417.45 mA h g−1. The Coulombic efficiency
is approximately 47.35%, which can mainly be ascribed to the
formation of SEI film. The discharge capacity is reduced to
505.1 mA h g−1 in the second cycle. After the initial cycles,
discharge capacity increases substantially to 540 mA h g−1
(85th cycle) and Coulombic efficiencies reach ∼99% after 23
cycles. The above results indicate that electrochemical
properties of compound 1 possess well cycling stability and
reversibility as anode materials for LIBs.
The rate capability and cycling stability are very crucial for
practical applications. Thus, rate capability of 1 has been
investigated at different current densities (50−500 mA g−1). As
illustrated in Figure 5d, the discharge capacities decreased from
426.8 to 313.4, 244.9, 171.4, 102.8, and 55.1 mA h g−1,
corresponding to 100, 200, 400, 1000, 2000, and 5000 mA g−1,
respectively. The reversible capacity of material is 392.5 mA h
g−1 when current density became 100 mA g−1 again, revealing
good stability of 1 as anode material.
A better insight into the charge−discharge performance of
compound 1 could be obtained by high current density test. In
the first 10 cycles, the material was activated by current density
of 50 mA g−1 before testing at 1000 mA g−1. As seen from
Figure 6, reversible capacity of this material is 224.6 mA h g−1
after 300 cycles with good capacity retention.
Figure 6. Coulombic efficiency and charge−discharge capacity at
1000 mA g−1.
Electrochemical impedance spectroscopy has been measured
to deeply understand electrochemical properties of 1 at
different open-circuit voltages during the first discharge−
charge process (Figure S16). The Nyquist plot exhibits a
sloped line and a semicircle at low frequencies and midhigh
frequencies, respectively. Before the cycle, the impedance value
was 1004 Ω. The total resistance was 203 Ω after the cycle,
which indicates that the 5-fold interpenetrated network of 1 is
helpful for electron conductivities and Li+ insertion/extraction.
The result is consistent with good rate performance and high
Coulomb efficiency.
CONCLUSIONS
In summary, we have constructed a novel functionalized
POMOF, namely {[PMo8 Mo4 O37(OH)3Zn4][BPE]2}·
[BPE] (1) by hydrothermal synthesis. In compound 1, Zn4-
ε-Keggin units were connected by organic linkers BPE to
generate a 3D dia network with 5-fold interpenetration.
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ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.9b01977.
■
S
Materials and instruments, additional structural draw-
ings, TGA, IR spectra, PXRD patterns, gas sorption
isotherms, electrochemical impedance spectroscopy, and
NMR spectra, and tables of bond lengths and angles and
X-ray crystallographic data for 1 (PDF)
Accession Codes
CCDC 1914191 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/data_request/cif, or by emailing
data_request@ccdc.cam.ac.uk, or by contacting The Cam-
bridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
Corresponding Author
*E-mail: yanxu@njtech.edu.cn. (Y.X.).
ORCID
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(16) Zhou, Z.; He, C.; Xiu, J.; Yang, L.; Duan, C. Metal-organic
polymers containing discrete single-walled nanotube as a heteroge-
neous catalyst for the cycloaddition of carbon dioxide to epoxides. J.
Am. Chem. Soc. 2015, 137, 15066−15069.
Yan Xu: 0000-0001-6059-075X
Author Contributions
(17) Gao, W. Y.; Chen, Y.; Niu, Y.; Williams, K.; Cash, L.; Perez, P.
J.; Wojtas, L.; Cai, J.; Chen, Y.; Ma, S. Crystal engineering of an nbo
topology metal-organic framework for chemical fixation of CO2 under
ambient conditions. Angew. Chem., Int. Ed. 2014, 53, 2615−2619.
(18) Ema, T.; Miyazaki, Y.; Shimonishi, J.; Maeda, C.; Hasegawa, J.-
y. Bifunctional porphyrin catalysts for the synthesis of cyclic
carbonates from epoxides and CO2: structural optimization and
mechanistic study. J. Am. Chem. Soc. 2014, 136, 15270−15279.
(19) Martín, C.; Fiorani, G.; Kleij, A. W. Recent advances in the
catalytic preparation of cyclic organic carbonates. ACS Catal. 2015, 5,
1353−1370.
#Y.-S.X. and W.-W.C. contributed equally to this work.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the Natural Science Foundation
of China (Grant 21501147, 21571103), the Major Natural
Science Projects of the Jiangsu Higher Education Institution
(Grant No. 16KJA150005), Jiangsu Planned Projects for
Postdoctoral Research Funds (Grant 1701097C), and the
Project of Priority Academic Program Development of Jiangsu
Higher Education Institutions (PAPD).
(20) Qu, J.; Cao, C.-Y.; Dou, Z.-F.; Liu, H.; Yu, Y.; Li, P.; Song, W.-
G. Synthesis of cyclic carbonates: catalysis by an iron-based composite
and the role of hydrogen bonding at the solid/liquid interface.
ChemSusChem 2012, 5, 652−655.
(21) Wang, X.; Zhou, Y.; Guo, Z.; Chen, G.; Li, J.; Shi, Y.; Liu, Y.;
Wang, J. Heterogeneous conversion of CO2 into cyclic carbonates at
ambient pressure catalyzed by ionothermal-derived meso-macro-
porous hierarchical poly(ionic liquid)s. Chem. Sci. 2015, 6, 6916−
6924.
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