Synthesis and Characterization of a Crown-Shaped 36-Molybdate Cluster and Application in Catalyzing Knoevenagel Condensation

Article abstract of DOI:10.1021/acs.inorgchem.0c01122

A novel crown-shaped 36-molybdate cluster with organophosphonate-functionalized polyoxomolybdates, (NH4)17Na7H12[Co(H2O)TeMo6O21{N(CH2PO3)3}]6·42H2O, has been successfully synthesized and well-characterized. It owns the highest nuclearity in the family of organophosphonate-based polyoxometalates reported so far. Furthermore, for the first time in the field, we illustrated that polyoxomolybdate could work as an effective heterogeneous catalyst for the Knoevenagel condensation reaction with high TOF (7714 h-1) and good recyclability. Impressively, the catalytic performance of 1 was also tested successfully in a large scale (～10 g) reaction, where 89percent of reaction yield and 3216 of TON were afforded.

Full text of DOI:10.1021/acs.inorgchem.0c01122

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Article
Synthesis and Characterization of a Crown-Shaped 36-Molybdate
Cluster and Application in Catalyzing Knoevenagel Condensation
Qiaofei Xu, Baijie Xu, Hui Kong, Peipei He, Jiawei Wang, Thirumurthy Kannan, Pengtao Ma,
Jingping Wang,* and Jingyang Niu*
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ABSTRACT: A novel crown-shaped 36-molybdate cluster with
organophosphonate-functionalized polyoxomolybdates,
(NH4)17Na7H12[Co(H2O)TeMo6O21{N(CH2PO3)3}]6·42H2O,
has been successfully synthesized and well-characterized. It owns
the highest nuclearity in the family of organophosphonate-based
polyoxometalates reported so far. Furthermore, for the first time in
the field, we illustrated that polyoxomolybdate could work as an
effective heterogeneous catalyst for the Knoevenagel condensation
reaction with high TOF (7714 h−1) and good recyclability.
Impressively, the catalytic performance of 1 was also tested
successfully in a large scale (∼10 g) reaction, where 89% of
reaction yield and 3216 of TON were afforded.
performance of alkaline disilicoicosatungstates [H(γ-
SiW10O32)2(μ-O)4]7− and [SiW10O36]8− for the Knoevenagel
condensation reaction.13 Since then, decent catalytic perform-
ances were reported for the Knoevenagel condensation
reaction when using [γ-H2GeW10O36]6−,14 [PW9O34]9−,15
INTRODUCTION
■
Polyoxometalates (POMs) have received significant attention
for their controllable and diverse structures and enormous
potential applications1 especially in catalytic chemistry.2
Structurally, POMs are constructed by the corner-, edge-, or
face-shared orientation of the polyhedra of early transition
metals (TMs) (MOx) (M = VV, NbV, TaV, MoVI, and WVI) in
their highest oxidation state, where M could be partly
substituted by Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Ru,
Pd, Ag, Hf, Ln, and so on.3 Those TM-substituted POMs have
been attracting significant attention for their effective catalytic
performance.4
Olefination is one of the most fundamental transformations,
which plays an important role in both academia and industry.5
As a typical CC bond-forming reaction, the Knoevenagel
condensation reaction is an important method to produce
olefins via the coupling reaction of carbonyl compounds and
active methylene groups in the presence of base catalysts along
with the loss of molecular H2O under certain conditions,
where the products have exhibited considerable importance in
the fields of organic synthesis, perfumes, pharmaceuticals, and
polymers.6 Traditionally, solid bases, Lewis acids and organo-
metallic compounds were applied as catalysts for this
transformation, though they come with some disadvantages,
for example, lack of efficiency, robustness, and recyclability.7 In
recent years, considerable research efforts have been focused
on investigating new catalysts for this reaction, such as ionic
liquids,8 layered double hydroxides,9 nitrogen-doped carbon,10
amine-functionalized materials silica,11 MOFs,12 and POMs. In
2007, Mizuno et al. first reported the good catalytic
16
17
18
[SiNb12O40]16−
,
[Nb10O28]6−
,
[Nb6O19]8−
,
and
[Ta6O19]8−.19 Furthermore, several composite materials
including Keggin-type H3PW12O40·xH2O20 have also exhibited
excellent catalytic performances in this transformation process.
It was reported that a coexisting Lewis acid and base
environment would be beneficial toward achieving Knoevena-
gel condensation,21 which is exactly coincident with TMs
(working as Lewis acid sites) and nucleophilic surface oxygen
atoms (working as Lewis base sites) in POMs. Hence, it opens
a possible path to apply TM-substituted POMs for
Knoevenagel condensation reaction. So far, successful
applications of POMs in catalyzing Knoevenagel condensation
are still limited to NbV-, TaV-, and WVI-incorporated POMs; as
part of the efforts to expand the POMs based catalyst family,
we are strongly inspired to explore new possibilities of
developing novel polyoxomolybdates based catalysts.
Organophosphonate-functionalized POMs as a subclass of
POMs have received much attention due to its structural
Received: April 17, 2020
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Scheme 1. Schematic Representation of the Synthetic Strategy Including the Disassembly of the [Mo7O24]6− and the
Subsequent Reassembly into 1 upon Addition of Appropriate Heteroatom, Cobalt, and ATMP
diversity and superior properties in last 20 years, which has
been intensively investigated by Pope,22 Zubieta,23 Mialane,24
Kortz,25 and and others.26 According to the previous
literatures,27 amino trimethylene phosphonic acid (ATMP),
as a multidentate and flexible triphosphate ligand is competent
to construct original structures. Besides, tellurium as
heteroatom has been developed in POMs chemistry;28
however, it is seldom found in organophosphonate-function-
alized polyoxomolybdates. Hence, a novel crown-shaped 36-
molybdate cluster (NH4)17Na7H12[Co(H2O)TeMo6O21{N-
(CH2PO3)3}]6·42H2O (1) was synthesized via the disassembly
of ammonium heptamolybdate and reassembly of the
dissociated products, amino trimethylene phosphonic acid
(ATMP), heteroatoms, and cobalt (Scheme 1). Notably, 1 was
the first reported polyoxomolybdate with a superior catalytic
performance for the Knoevenagel condensation reaction. A
turnover number (TON) of 3051 and a turnover frequency
(TOF) of 7714 h−1 were obtained. Significantly, the scale-up
experiment has shown that 89% reaction yield and 3216 TONs
could be observed when the reaction was conducted with
benzaldehyde (14.1 g) and ethyl cyanoacetate (10.5 g) at 70
°C for 3 h, which presents huge potentials of this catalyst in
real application.
Table 1. Crystal Data and Structure Refinement for 1
empirical formula
formula weight
crystal system
space group
a (Å)
b (Å)
c (Å)
β (deg)
C18H212Co6Mo36N23Na7O228P18Te6
9691.38
monoclinic
I2/a
35.612(5)
29.198(4)
36.086(4)
119.002(10)
32817(8)
4
volume (Å3)
Z
Dcal (g/cm3)
1.790
μ (mm−1
F (000)
Rint
)
2.317
16508.0
0.0611
1.102
GOF on F2
−42 ≤ h ≤ 39
−31 ≤ k ≤ 34
−43 ≤ l ≤ 40
0.0761, 0.1929
0.1309, 0.2619
limiting indices
R1, wR2 [I > 2σ(I)]
R1, wR2 [all data]
been synthesized as follows: Ammonium heptamolybdate (0.96 g,
0.78 mmol) was dissolved in 15 mL of NaAc-Hac (pH 5.5, 1M) buffer
solution followed by the addition of Na2TeO3 (0.10 g, 0.45 mmol),
ATMP (0.27 g, 0.90 mmol), and CoCl2·6H2O (0.24 g, 1.0 mmol)
with stirring the solution. Afterward, the pH of the reaction mixture
was adjusted to 5.00 by 6 M NaOH aqueous solution, leading to a
muddy amaranth color. After it was stirred at 80 °C for 2 h, the mixed
solution was gradually cooled to room temperature, filtered, and
allowed to evaporate slowly at room temperature. The amaranth
block-shaped crystals of 1 were obtained after about 10 days. Yield:
76% for 1 based on CoCl2·6H2O. Elemental analysis (%) calcd: Mo,
35.64; Co, 3.65; Na, 1.65; P, 5.75; C, 2.23; N, 3.32; H, 2.21. Found:
Mo, 35.98; Co, 3.67; Na, 1.76; P, 5.83; C, 2.25; N, 3.28; H, 2.01.
Selected IR (KBr, cm−1; s, strong; m, medium; w, weak): 3468 (s),
1628 (s), 1421 (s), 1325 (w), 1223 (m), 1096 (s), 1063 (s), 993 (m),
978 (m), 931 (m), 893 (s), 775 (s), 725 (s), 654 (s), 595 (s).
General Procedure for Knoevenagel Condensation. The
substrates (ethyl cyanoacetate, 5 mmol; aldehydes, 7.5 mmol),
catalyst (0.02−0.06 mol %, 9.7−29.1 mg), and solvent (2.5 mL) were
added into a tube at room temperature. The reaction mixture was
stirred and heated for 3 h at 50−80 °C on the parallel reactor of
WATTCAS-1020H (Figure S13). The products were conducted with
qualitative detection by GC−MS, and the yields were monitored by
EXPERIMENTAL SECTION
■
Materials and Methods. All reagents for the syntheses were
obtained commercially without further purification. Elemental
analyses of C, H, and N were performed with an Elementar Vario
Elcube CHNS analyzer (PerkinElmer, Waltham, MA, USA).
Elemental analysis for Mo, Co, and P were performed with a Perkin
Eimer Optima 2100 DV (PerkinElmer, Waltham, MA) inductively
coupled plasma optical emission spectrometer. IR spectra were
recorded on a Bruker VERTEX 70 IR spectrometer (Nicolet,
Madison, WI) (using KBr pellets) in the range of 4000−400 cm−1.
X-ray powder diffraction (XRPD) data were recorded on a Bruker
AXS D8 Advance diffractometer (Bruker, Karlsruhe, Germany) with
Cu Kα radiation in the angular range 2θ = 5−40° at 293 K.
Thermogravimetry analysis (TGA) was carried out on NETZSCH
STA449F5/QMS403D instrument (Mettler-Toledo, Schwerzenbach,
Switzerland) with a heating rate of 10 °C min−1 from 25 to 800 °C in
N2 flow. X-ray photoelectron spectroscopy (XPS) was performed on
an Axis Ultra (Kratos, Manchester, UK) apparatus using mono-
chromatic Al Kα radiation.
Synthesis of (NH4)17Na7H12[Co(H2O)TeMo6O21{N-
(CH2PO3)3}]6·42H2O (1). Caged-shaped cobalt-containing 1 has
B
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Figure 1. Polyhedral/ball-and-stick representation of the polyanionic skeleton of 1 (a) and side view (b). Simplification of the polyanionic skeleton
in 1 (c) and side view (d). (e) Ball-and-stick representation of three subunits. (f) Polyhedral/ball-and-stick representation of
[Co(H2O)TeMo6O21{N(CH2PO3)}3]6− subunit. (g) Polyhedral/wires or sticks representation of [TeMo6O21] unit. (h) Coordination mode of
cobalt atom. (MoO6/Mo: sky blue, Te: gray 50%, P: yellow, Co: pink, C: black, N: blue, O: red, H: gray 25%).
GC. After completion of the reaction, heterogeneous catalyst 1 could
be recovered easily from the mixture of solvent/substrates/catalyst by
centrifugation at the end of every reaction cycle, by using ethyl acetate
to wash the catalyst 3 times and then drying it in oven at 70 °C. For
scale-up of the experiment, ethyl cyanoacetate (90 mmol), aldehydes
(135 mmol), 1 (0.025 mmol, 240 mg), and methanol (45 mL) were
mixed in the flask at 70 °C for 3 h, and the product was analyzed
using the same procedure as just described (Figure S14).
number for 1 is 1940537. Collected crystal data and structure
refinement parameters for 1 are given in Table 1.
RESULTS AND DISCUSSION
■
Structural Description. Single-crystal X-ray diffraction
analysis revealed that 1 is located on the 2-fold axis and
crystallizes in the monoclinic space group I2/a. The structure
of 1 contains one giant [Co(H2O)TeMo6O21{N-
X-ray Crystallographic Determination. Crystallographic study
for 1 was performed at 296(2) K on a Bruker Apex-II CCD
diffractometer using graphite-monochromated Mo Kα radiation (λ =
0.71073 Å). Intensity data were corrected for Lorentz and polarization
effects as well as for multiscan absorption by an applied multiscan
absorption correction SADABS program. Structure solution was
carried out by direct methods (SHELXS97), and Fourier syntheses
were improved with the SHELXL refinement package applying least-
squares minimization algorithm. In the final refinement cycles, the
Mo, Te, Co, and P atoms were refined anisotropically; the O, C, and
N atoms were refined isotropically. The hydrogen atoms of organic
groups were fixed in calculated positions and then refined using a
riding model. Although the crystal data and structure refinement
results revealed that the empirical formulas was
C18H36Co6Mo36N6Na7O201P18Te6, the SQUEEZE program per-
formed in PLATON was further used to calculate and evaluate the
possible numbers of the solvent water molecules in the accessible
voids of the crystal structures where total of 148 H2O molecules and
36−
(CH2PO3)3}]6
polyanion, 17 ammoniums, 7 Na+ cations,
42 water molecules, and 12 H3O+. The polyanions of 1 (Figure
1a,b) is a crown-shaped triphosphonate-based polyoxomolyb-
date in large size, which includes six ATMP, six cobalt atoms,
and six [TeMo6O21] building blocks (Figure 1g). It can be
observed from the simplification of the polyanion (Figure 1c),
six [Co(H2O)TeMo6O21{N(CH2PO3)}3]6− subunits con-
nected alternatively by the P−OMo linkers bridged (Figure
1d) leading to a cavity of about 4.2 Å in diameter. In details,
the [Co(H2O)TeMo6O21{N(CH2PO3)3}]6− subunit (Figures
1f and S1b) was generated via two μ2-O linkers from one
{PO3} group in ATMP bridged two edge-sharing {MoO6}
octahedrons in the [TeMo6O21] unit and ATMP, with one
cobalt atom mounted inside. To clearly illustrate the
connection among the subunits, three of these were selected
for description. As shown in Figure 1e, there are two remaining
{PO3} groups of ATMP in subunit 1 linking the two
neighboring subunits (subunit 2 and 3), respectively. More-
over, two {PO3} groups of the ATMP in subunit 2 and 3
bonded with the other four {MoO6} octahedrons in subunit 1.
In addition, the rest two {MoO6} octahedrons and one {PO3}
groups in subunit 2 and 3 were paired with the other
+
17 NH4 should be added to the chemical formulas:
(NH4)17Na7H12[Co(H2O)TeMo6O21{N(CH2PO3)3}]6·148H2O.
However, the TGA and CHN elemental analysis results showed that
the number of H2O molecules might be 42 for the empirical formulas:
(NH4)17Na7H12[Co(H2O)TeMo6O21{N(CH2PO3)3}]6·42H2O. This
might be attributed to the weathering of crystal of 1. The CCDC
C
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Figure 2. Knoevenagel condensation reaction of benzaldehyde with ethyl cyanoacetate at different reaction conditions: (a) catalyst loading; (b)
reaction temperature; (c) reaction solvent; (d) reaction time. Turn over frequency (TOF) = conversion of ethyl cyanoacetate (mmol)/(catalyst
(mmol) × 5/60 (h)). Turn over number (TON) = conversion of ethyl cyanoacetate (mmol)/(catalyst (mmol)).
contiguous subunits. That being said, two {MoO6} octahe-
drons and one {PO3} group in the subunit can be bonded with
the corresponding one {PO3} group and two {MoO6}
octahedrons in other adjacent subunits; as a result, the
where only minimum products could be observed in the
absence of catalysts. When each composite of the raw materials
(CoCl2, ATMP, ammonium heptamolybdate Na2TeO3) was
tested as homogeneous catalysts, no desired product was
detected for either CoCl2 or ATMP, though 3a was obtained
with 74% yield in the presence of ammonium heptamolybdate.
In contrast, when 1 was employed as the catalyst, the reaction
yield of desired product 3a improved to 88%, which makes 1
stand out as an optimal catalyst for Knoevenagel condensation
reaction, and its heterogeneity also helps recovering the
catalyst easily for reusability.
To investigate reaction conditions, such as reaction
temperature, catalyst loading, reaction time and solvent, a
series of condensation reactions of benzaldehyde and ethyl
cyanoacetate have been conducted using 1 as the catalyst, with
results summarized in Figure 2a. The product 3a with 89%
yield and 4432 TONs were achieved when the dosage of
catalyst was 0.02 mol %. With the further increase of catalyst 1
(0.03−0.06 mol %), the yield of 3a continued to improve but
TONs sacrificed significantly, as a result, 0.03 mol % was used
as the optimal catalyst loading. At the same time, several
condensation reactions of benzaldehyde with ethyl cyanoace-
tate were carried out at different temperatures, as illustrated in
Figure 2b. Particularly, in the range of 50 to 70 °C, both the
reaction yield and TOF improved significantly along with
increasing temperature. No obvious optimizations observed
when continuing to rise temperate 80 °C. As a result, 70 °C
36−
crown-shaped [Co(H2O)TeMo6O21{N(CH2PO3)3}]6 poly-
anion was generated with a cavity approximately 4.4 Å in
diameter. Furthermore, each cobalt atom was bonded with one
nitrogen atom and three oxygen atoms from ATMP plus one
water molecule. Therefore, it exhibits a trigonal bipyramid
geometry as shown in Figure 1h, which is in good agreement
with the previous literature.29 Moreover, the structure of
[TeMo6O21] units are different from the classic Anderson-type
of POMs where there is a tricoordinated heteroatom located in
the center. The ball-and-stick view, space-filling view, and
polyhedral/ball-and-stick view (from different perspectives) of
the polyanion in 1 have also been presented in Figures S1 and
S2 to better illustrate its structure. As shown in Figure S3, the
polyanions could generate a 2D layer and 3D structure via the
connection of cations.
Catalytic Performance for Knoevenagel Condensa-
tion. Because of the coexistences of cobalt and nucleophilic
nature of surface-oxygen atoms in 1, compound 1 potentially
own the property like Lewis acids and bases concurrently,
making it a promising catalyst for Knoevenagel condensation
reaction. Initially, the condensation reaction of benzaldehyde
and ethyl cyanoacetate as model reactions has been evaluated
via using different catalysts, with results presented in Table S5,
D
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a
Table 2. Knoevenagel Condensation of Various Aldehydes with Ethyl Cyanoacetate in the Presence of 1
a
Reaction conditions: catalyst, 0.03 mol %; ethyl cyanoacetate, 5 mmol; aldehydes, 7.5 mmol; solvent, methanol; time, 3 h; temperature, 70 °C.
b
reaction yields measured based on GC with methylbenzene as internal standard. All of the products were identified by GC−MS spectra and GC
c
spectra. TON (turn over number) = conversion of ethyl cyanoacetate(mol)/catalyst(mol) used. Ortho-: ortho substituent; Meta-: meta
substituent; Para-: para substituent.
was chosen as the optimal temperature condition, where 92%
reaction yield and 7714 h−1 TOF were observed. Additionally,
experiments were also conducted in different solvents
(CH3OH, H2O, CH3COCH3, and CH3CN), with reaction
results presented in Figure 2c. Obviously, CH3OH was tested
as a more proper reaction solvent, where the product was
afforded in 92% reaction yield and 3051 TONs; we believe in
this reaction, protic solvent would be helpful in boosting
catalytic performance. As shown in Figure 2d, the reaction
yield and TON values increased when the reaction time
increased from 0.5 to 3 h. No doubt that the high TON and
TOF values have made compound 1 a promising catalyst to
accomplish Knoevenagel condensation reaction.
Encouraged by the results as discussed above, we further
extended the investigations into different substrates under the
optimal reaction conditions. As illustrated in Table 2, the
reaction with benzaldehyde gave desired product 3a in 92%
yield and 3067 TONs as control (Table 2, entry 1). High
reaction yields (95−99%) were achieved for multiple aromatic
aldehydes with different substituted groups, including electron-
donating and -withdrawing groups (2-OCH3−, 2-NO2, 3-Cl, 3-
Me, 4-Me, 4-OCH3, 4-Br, 4-Cl, 4-F, etc.). Impressively, 4-
fluorobenzaldehyde and 4-chlorobenzaldehyde also exhibited
satisfactory reaction yields in 97 and 98%, respectively.
Hexahydro-benzaldehyde was also studied as an example of
nonaromatic aldehyde where a decent reaction yield of 80%
was achieved. Satisfactorily, we are convinced that compound
1 is able to catalyze the Knoevenagel condensation reaction
with high tolerance of different groups in high effective
manner.
The reusability of the catalyst was also evaluated by
repeatedly using 1 to catalyze Knoevenagel condensation of
benzaldehyde with ethyl cyanoacetate at 70 °C for 3 h in
multiple cycles. In each cycle, upon reaction completion,
heterogeneous catalyst 1 (undissolved in methanol, Figure
S11) was easily collected from the mixture of solvent/
substrates/catalyst by centrifugation, followed by three
washings with methanol and drying at 70 °C. Recovered
catalyst 1 was characterized by infrared spectrum to ensure no
structural changes in the catalyst and proceeding with the next
reaction cycle. The recyclability study results of 1 have been
shown in Figure S9, which indicates no obvious catalytic
activity decrease nor structure changes of 1 observed after 4
reaction cycles. Finally, a scale-up experiment was also carried
out (Figure S14), where benzaldehyde (14.1 g) reacted with
ethyl cyanoacetate (10.5 g) at 70 °C for 3 h in the presence of
catalyst 1, where satisfactory reaction yield of 89% was
obtained, making it a very promising alternative catalyst in
practical applications.
CONCLUSIONS
■
In summary, a novel cage-shaped 36-molybdo-18-phosphonate
has been synthesized by the disassembly of heptamolybdate
and the reassembly of reactants, where cobalt was grafted into
the polyanions by ATMP. First, compound 1 represents the
largest organophosphonate-based POMs so far, exceeding the
E
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size of previously reported 24-molybdate clusters. Besides, 1 is
reported as the first polyoxomolybdate with remarkable
catalytic effectiveness for the Knoevenagel condensation
reaction. Furthermore, 1 exhibits good reusability with still
85% yield available after four repeated reaction cycles. Notably,
reaction in large scale (10.5 g of ethyl cyanoacetate, 90 mmol)
also shows well-preserved reaction yield (89%), strengthening
its potential in real applications. Finally and most importantly,
we illustrated a feasible synthetic strategy to make novel
organophosphonate-functionalized polyoxometalates with ap-
pealing chemical properties, and we hope this method can help
to open more possibilities in expanding the POM family.
Thirumurthy Kannan − Henan Key Laboratory of
Polyoxometalate Chemistry, Institute of Molecule and Crystal
Engineering, College of Chemistry and Chemical Engineering,
Henan University, Kaifeng, Henan 475004, PR China
Pengtao Ma − Henan Key Laboratory of Polyoxometalate
Chemistry, Institute of Molecule and Crystal Engineering,
College of Chemistry and Chemical Engineering, Henan
University, Kaifeng, Henan 475004, PR China
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.inorgchem.0c01122
Author Contributions
All authors have given approval to the final version of the
manuscript.
Notes
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.inorgchem.0c01122.
■
sı
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
Structures, characterization, catalytic experiments, mass
spectrum for the corresponding product, catalytic device
and scale-up experiment (PDF)
■
We gratefully acknowledge support from the NSFC (2117205)
and the Natural Science Foundation of Henan Province
(162300410015).
Accession Codes
CCDC 1940537 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.
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Jingping Wang − Henan Key Laboratory of Polyoxometalate
Chemistry, Institute of Molecule and Crystal Engineering,
College of Chemistry and Chemical Engineering, Henan
University, Kaifeng, Henan 475004, PR China;
Email: jpwang@henu.edu.cn
Jingyang Niu − Henan Key Laboratory of Polyoxometalate
Chemistry, Institute of Molecule and Crystal Engineering,
College of Chemistry and Chemical Engineering, Henan
University, Kaifeng, Henan 475004, PR China; orcid.org/
0000-0001-6526-7767; Email: jyniu@henu.edu.cn
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Authors
Qiaofei Xu − Henan Key Laboratory of Polyoxometalate
Chemistry, Institute of Molecule and Crystal Engineering,
College of Chemistry and Chemical Engineering, Henan
University, Kaifeng, Henan 475004, PR China
Baijie Xu − Henan Key Laboratory of Polyoxometalate
Chemistry, Institute of Molecule and Crystal Engineering,
College of Chemistry and Chemical Engineering, Henan
University, Kaifeng, Henan 475004, PR China
Hui Kong − Henan Key Laboratory of Polyoxometalate
Chemistry, Institute of Molecule and Crystal Engineering,
College of Chemistry and Chemical Engineering, Henan
University, Kaifeng, Henan 475004, PR China
Peipei He − Henan Key Laboratory of Polyoxometalate
Chemistry, Institute of Molecule and Crystal Engineering,
College of Chemistry and Chemical Engineering, Henan
University, Kaifeng, Henan 475004, PR China
(4) (a) Su, X. F.; Guan, W.; Yan, L. K.; Lang, Z. L.; Su, Z. M.
Evidence of two-state reactivity in water oxidation catalyzed by
polyoxometalate-based complex [Mn3(H2O)3(SbW9O33)2]12‑. J. Catal.
2019, 376, 146−149. (b) Zhang, B.; Sun, G.; Ding, S.; Asakura, H.;
Zhang, J.; Sautet, P.; Yan, N. Atomically Dispersed Pt1-Polyoxome-
talate Catalysts: How Does Metal−Support Interaction Affect
Jiawei Wang − Henan Key Laboratory of Polyoxometalate
Chemistry, Institute of Molecule and Crystal Engineering,
College of Chemistry and Chemical Engineering, Henan
University, Kaifeng, Henan 475004, PR China
F
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