Synthesis and properties of a POM-based trinuclear copper(II) triazole framework

Article abstract of DOI:10.1039/c7ra12150d

A novel POM-based trinuclear copper(ii) triazole framework, namely, [H₂{Cu₆(trz)₆(μ₃-OH)₂}Mo₅O₁₈]·3H₂O (1) was isolated using a hydrothermal method, which displays a 3D network constructed from trinuclear copper(ii) units and triazole ligands with [Mo₅O₁₈]^6- anions as templates. 1 has been identified by single crystal X-ray diffraction, elemental analysis, thermogravimetric analysis, powder X-ray diffraction and FT-IR. Magnetic studies indicate that antiferromagnetic interactions exist in 1. In addition, 1 exhibits good Lewis acid catalytic activity for the synthesis of cyclohexanone ethylene ketal with 95% conversion. The HOMO-LUMO gap (E_g) of 1 is 2.34 eV calculated using the Kubelka-Munk equation (Fhν)^0.5, indicating that its forbidden bandwidth belongs to the semiconductor category. Visible-light photodegradation of RhB catalyzed by 1 was investigated, which shows high activity with an above 98% degradation rate.

Full text of DOI:10.1039/c7ra12150d

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Synthesis and properties of a POM-based trinuclear
copper(II) triazole framework†
Cite this: RSC Adv., 2018, 8, 2034
*
*
Li Xu, Ying Lu,
and Shuxia Liu
Liping Huang, Xiaohui Li, Shuang Wang, Zhong Zhang
A novel POM-based trinuclear copper(II) triazole framework, namely, [H2{Cu6(trz)6(m3-OH)2}Mo5O18]$3H2O
(1) was isolated using a hydrothermal method, which displays a 3D network constructed from trinuclear
6ꢀ
copper(II) units and triazole ligands with [Mo5O18
]
anions as templates. 1 has been identified by single
crystal X-ray diffraction, elemental analysis, thermogravimetric analysis, powder X-ray diffraction and FT-
IR. Magnetic studies indicate that antiferromagnetic interactions exist in 1. In addition, 1 exhibits good
Lewis acid catalytic activity for the synthesis of cyclohexanone ethylene ketal with 95% conversion. The
HOMO–LUMO gap (Eg) of 1 is 2.34 eV calculated using the Kubelka–Munk equation (Fhn)0.5, indicating
that its forbidden bandwidth belongs to the semiconductor category. Visible-light photodegradation of
RhB catalyzed by 1 was investigated, which shows high activity with an above 98% degradation rate.
Received 5th November 2017
Accepted 26th December 2017
DOI: 10.1039/c7ra12150d
rsc.li/rsc-advances
oxidation, giving a conversion rate of 100%. Mondal et al.6b
reported a series of MOFs based on TTC units, which show high
Introduction
activity in the photocatalytic degradation of toxic dye mole-
cules. Furthermore, due to their interesting magnetic proper-
ties, TCC clusters have attracted attention in the construction
of magnetic high-nuclear clusters and MOFs materials. For an
example, Ouellette et al. reported a microporous metal–organic
framework constructed with magnetic {Cu3(m3-OH)(trz)3}2+
building blocks.7
Polyoxometalates (POMs), as a class of nanosized metal-oxo
clusters composed of group VI (Mo and W) and group V (V,
Nb and Ta) elements in their highest oxidation state, have
received increasing attention owing to their aesthetically
appealing structures and wide applications such as in the elds
of magnetism,1 and catalysis.2 Due to their strong acidity and
fast multielectron transformation activity, POMs can be
employed as acid, redox and bifunctional (acid and redox)
catalysts in many synthetically useful organic reactions.
Moreover, they can act as excellent photocatalysts in the
oxidation of organic compounds owing to their ability as
electron and oxygen relays.3 Trinuclear triangular copper(II)
(TTC) clusters with the formula {Cu3(m3-OH)(L)3} (L ¼ pyrazole,
imidozole, triazole, terazole and the derivatives of them)
possess a planar structure composed of three copper centers
held together by a central m3-O atom.4 In the TTC cluster, each
Cu(II) center is coordinatively unsaturated with open coordi-
nation sites, which is a potential active site in Lewis acid and
oxidation catalytic reactions.5 Designing MOFs based on TTC
units have attracted great attention of researchers owing to
their promising applications in catalysis.5 For examples, Zhang
et al.6a synthesized a active-site-accessible porous MOF using
TTC as SBU, which shows high activity for the CO catalytic
Inspired by the properties of POMs and TTC clusters, we
explored to encapsulate POMs into the host matrix of MOFs
built by TTC units. Firstly, due to the promising catalytic
performances of both POMs and TTC units, the obtained POMs-
based TTC frameworks may show enhanced catalytic activity by
the combination and synergies of the functions of POMs and
TTC units. Secondly, the inlay of POMs into the host matrix of
MOFs built by TTC units would effectively enhance the stability
of both POMs and TTC frameworks, which is an essential
prerequisite for practical applications.8 Finally, the combina-
tion of magnetic TCC units and POMs, interesting magnetic
properties may be evoked. Although some POM-based MOFs
have been synthesized, to our knowledge, the POM-based MOFs
combined POM and TCC units have never been reported.
Herein, a POM-based trinuclear–copper(II) triazole framework,
[{H2Cu6(trz)6(m3-OH)2}Mo5O18]$3H2O (1) (trz ¼ 1,2,4-triazole),
has been successfully synthesized under hydrothermal condi-
tion. The catalytic performance of 1 was assessed by choosing
the synthesis of cyclohexanone ethylene ketal catalyzed by Lewis
acid and visible-light photodegradation of RhB as testing reac-
tions. In addition, the magnetic property of 1 has been
investigated.
Key Laboratory of Polyoxometalate Science of the Ministry of Education, College of
Chemistry, Northeast Normal University, Changchun, Jilin 130024, China. E-mail:
liusx@nenu.edu.cn; Fax: +86-431-85099328
† Electronic supplementary information (ESI) available: IR spectra, PXRD
patterns, TG curves, magnetic properties and additional experimental result
gures. CCDC 1571612. For ESI and crystallographic data in CIF or other
electronic format see DOI: 10.1039/c7ra12150d
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Synthesis of 1
Experimental
A mixture of Na2MoO4$2H2O (1.0 mmol, 0.242 g), (TBA)2[Mo6-
O19] (0.5 mmol, 0.638 g), CuCl2$2H2O (0.341 g, 2.0 mmol), trz
(2.0 mmol, 0.138 g) was added to distilled water (10 mL) with
stirring. Then the solution was stirred for 0.5 h and the pH was
adjusted to 5.2 with 1 M HCl solution. The resulting suspension
was transferred to a Teon-lined stainless-steel autoclave and
sealed. Aer being heated at 170 ꢁC for ve days, it was cooled to
room temperature at a rate of 10 ꢁC hꢀ1. Yellow block crystals of
1 were separated, washed with water and air-dried. Although
(TBA)2[Mo6O19] does not appear in the system, but he is
essential in the reaction, because we tried not to add it in the
system, has not been a product, it is due to (TBA)2[Mo6O19] was
decomposed into MoO6 polyhedron in the reaction system,
then, MoO6 polyhedron reactant with the MoO42ꢀ get the target
product 1. Yield: 0.19 g (30% based on Mo). Anal. calcd (%) for
1: C 8.76, H 1.23, N 15.33, Cu 23.17, Mo 29.16; found: C 8.80, H
1.22, N 15.32, Cu 23.20, Mo 29.14. IR (solid KBr pellet): 3268(s),
1559(w), 1373(w), 1221(w), 1045.99(w), 936(s), 823(s), 714(s),
Materials and methods
(TBA)2[Mo6O19] (TBA ¼ tetrabutylammonium) was prepared
according to the literature procedures.9 Other chemicals were
obtained commercially and used without further purication.
Crystal morphology was characterized by using a Quanta 250
FEG scanning electron microscope. Fourier transform infrared
spectroscopies (FT-IR) were recorded in the range 400–
4000 cmꢀ1 on an Alpha Centaurt FT-IR spectrophotometer
using KBr pellets. Single crystal XRD analysis of 1 were con-
ducted on a Bruker Smart Apex CCD diffractometer with Mo Ka
˚
monochromated radiation (l ¼ 0.71073 A) at room temperature.
Powder X-ray diffraction (PXRD) measurements were performed
˚
on a Rigaku D/MAX-3 instrument with Cu Ka (l ¼ 1.5418 A)
radiation in the angular range 2q 3–50ꢁ at 293 K. Thermogra-
vimetric analysis (TGA) was performed on a Perkin-Elmer TGA7
instrument, with a heating rate of 10 ꢁC minꢀ1 under a nitrogen
atmosphere. The magnetic susceptibility data were obtained on
a SQUID magnetometer (Quantum Design, MPMS-5) in the
temperature range 2–300 K with applied eld of 1000 Oe. GC
analyses were performed on an Agilent 6820 instrument with
a ame ionization detector.
602(s), 524(m), 409 (m) cmꢀ1
.
Results and discussion
Synthesis and crystal structure
Procedure for catalytic condensation of cyclohexanone and
glycol
The reaction of Na2MoO4$2H2O, (TBA)2[Mo6O19], CuCl2$2H2O,
trz and water under hydrothermal conditions generated yellow
block crystals of 1. Notably, the formation of 1 was highly
sensitive to the pH value of the reaction system, which was
controlled in the range of 5.2 to 5.5, and 1 could not be obtained
outside this pH range. Although (TBA)2[Mo6O19] does not
appear in the composition of 1, it is essential for the synthesis of
1. We cannot obtain 1 in the absence of (TBA)2[Mo6O19]. It may
be due to (TBA)2[Mo6O19] decomposed into MoO6 polyhedra in
The ketalization reaction was performed in a three-necked
round-bottomed ask with a given mass of 1. Then, reason-
able volume ratio of cyclohexanone and ethylene glycol, and
cyclohexane were added with magnetic stirring, the device was
equipped with thermometer reuxing condenser tube and
water segregator in atmospheric pressure in 3 hours. The
solution was heated to boil and reuxed until no water owed
off. The resultant solution was distilled and puried. Samples
should be taken every half an hour, and the sample should be
diluted with acetone, the yield of cyclohexanone ethylene ketal
can be measured by GC analysis with sample diluted by acetone.
2ꢀ
the reaction system, then MoO6 polyhedra react with MoO4
yielding the target product 1. The SEM image showed that 1 was
block crystal and its surface was slippy (Fig. S2, ESI†). The PXRD
pattern of 1 and the simulated PXRD pattern are shown in
Fig. S5, ESI.† The diffraction peaks on the patterns correspond
well in position, conrming that the product is in a pure phase.
Procedure for photocatalysis of RhB
1 displayed a trinuclear copper triazole framework with
6ꢀ
The photodegradation of RhB is evaluated under Xe light [Mo5O18
]
anions as templates. There are three Cu2+ ions, six
irradiation from high pressure Xe lamp through a typical trz ligands, one [Mo5O18]6ꢀ anion and one coordination water
process: 10 mg of the compound 1 was mixed together with molecule in the basic structural unit of 1. Three Cu2+ centres are
100 mL of 10 mg Lꢀ1 RhB solution in a beaker by ultrasonic connected by a m3-O and each pair of adjacent Cu2+ was con-
dispersion for 30 min until reached the surface adsorption nected by a triazole ligand to form a three core triangular
equilibrium on the particles of compound 1. Then, the mixture Cu3(m3-OH)(trz)3 unit (Fig. 1). In the trinuclear copper unit,
was stirred continuously under visible light irradiation. At 0, three Cu2+ centres display distinct coordination environments:
20, 40, 60, 90, 120, 150, 180 and 200 min, 3 mL of the sample Cu1 was coordinated by the m3-O atom, O atom from [Mo5O18]6ꢀ
was taken out from the beaker respectively, followed by anions and three N from trz; Cu2 was connected with the m3-O
centrifugation to remove 1 and a clear solution was obtained atom, three N atoms from trz ligands and one Ow atom. Cu3 was
for UV-vis analysis. The UV-vis diffuse reectance (DR) spec- coordinated by the m3-O atom, one O atom from a [Mo5O18]6ꢀ
trum of 1 was recorded between 380 and 550 nm. The photo- anion and three N atoms from trz. The average Cu–O and Cu–N
6ꢀ
˚
˚
decomposition rate was calculated by the formula: D (%) ¼ (A0 bond distances are 2.151 A and 1.994 A, respectively. [Mo5O18]
ꢀ At)/A0 ꢂ 100%; D is the degradation rate; A0 is the initial anion is constructed by three MoO6 octahedra and two MoO5
absorption; At is the concentration aer a period of reaction polyhedra by corner-sharing connections with Mo–O bond
˚
time.
lengths in the range of 1.707–2.606 A. In the structure of 1, each
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Fig. 1 (a) Diagram of the structural unit of 1. (b) Diagram of the tri-
nuclear copper(II) triazole framework in compound 1. (c) 3D structure
of 1. (d) Diagram of the trinuclear copper(II) triazole framework with
6ꢀ
[Mo5O18
]
guests. Color codes: MoO6: deep green; O: red; N: blue
spheres; C: gray; Cu: light blue.
Fig. 2 PXRD patterns of 1: (a) the immersion of 1 in different solvents.
(b) The immersion of compound 1 in aqueous solutions with different
pH values.
Cu3(m3-OH)(trz)3 unit connects with each other leading to a 3D
trinuclear copper triazole framework with [Mo5O18
templates.
]
6ꢀ anions as
K3HMo5O17 was not stable in glycol and aqueous solution with
pH $ 10. Cu3(trz)3(OH)3(H2O)4 was stable in all of these organic
solvents, but it was not stable in aqueous solution with pH $ 10.
The above results show that the chemical stability of 1 is better
than K3HMo5O17 and Cu3(trz)3(OH)3(H2O)4, which is attributed
to the structure of 1, the introduction of POM into TTC MOFs
making 1 more stable.
Thermal stability
The stability of 1, K3HMo5O17 (ref. 10) and Cu3(trz)3(OH)3(H2O)4
(ref. 6) was initially researched by means of thermogravimetric
analysis (TGA). For 1, a gradual mass loss of 3.7% between 38–
330 ꢁC is assigned to the loss of two crystal lattice H2O and one
coordinated H2O (calcd 3.3%). Then, 51.3% weight loss occurs
in the specied temperature region of 450–620 ꢁC, which can be
ascribed to the loss of the six triazole ligand and two hydroxyl
(calcd 50.6%), which demonstrates that the main framework of
compound 1 was stable until 450 ꢁC (Fig. S6, ESI†). While
UV-vis spectroscopy
The UV-vis diffuse reectance absorption spectrum of
compound 1, K3HMo5O17 and Cu3(trz)3(OH)3(H2O)4 were tested
as presented in Fig. 3, S10 and S11, ESI.† The result showed that
their Eg were 2.34 eV, 2.87 eV and 1.67 ev, respectively. We take 1
as model to show the relationship of UV-vis diffuse reectance
absorption spectrum and Eg. In the ultraviolet range, the lowest
energy band at 265 nm can be assigned to the charge–transfer
ꢁ
K3HMo5O17 and Cu3(trz)3(OH)3(H2O)4 were stable until 525 C
and 350 ꢁC according their TG curves, respectively (Fig. S7 and
S8, ESI†).
Chemical stability
1 was air-stable because no efflorescence of the crystal was transition from O / Mo, the higher energy band at 780 nm
observed. Aer being steeped in common organic solvents arises from the d–d electronic transition of the Cu centers.10 The
(such as dimethylformamide, dichloromethane, methanol, optical band gaps (Eg) of 1 have been calculated using Tauc's
acetone, hexanone and glycol) for 5 days at room temperature, relation:11 (ahn) ¼ A(hn ꢀ Eg)n; where a, n, h, n, Eg and A stand for
there were no changes in its PXRD patterns demonstrated that 1 absorption coefficient, frequency, Planks' constant, transition
was stable in these organic solvents (Fig. 2a). Furthermore, 1 coefficient, band gap and band tailing parameter, respectively.
was stable in acid and basic aqueous solution with pH range Among them, A is a constant and a is the optical absorption
from 2 to 12 (Fig. 2b). In order to compare the chemical stability coefficient given by the Kubelka–Munk function: F(RN) ¼ (1 ꢀ
of 1, K3HMo5O17 and Cu3(trz)3(OH)3(H2O)4, we measured the RN)2/2RN, RN ¼ (I/Io)diff is the diffuse reectivity. The index n
PXRD patterns of K3HMo5O17 and Cu3(trz)3(OH)3(H2O)4 under is
a number which characterizes the transition process
the same condition (Fig. S9, ESI†). The result showed that involved. The intercept of the linear plots (ahn)n with the E-axis
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correspondent with the previously report6 about TTC
compound, antiferromagnetic interactions existing in the TTC
core.
Catalysis for condensation reaction of cyclohexanone and
glycol
In many organic reactions, carbonyl protection reaction is one
of the most important intermediate processes. Cyclohexanone
reacts with glycol to form cyclohexanone ethylene ketal is
a typical carbonyl protection reaction, in which acid catalyst
plays a signicant role.12 Herein, we chose the synthesis of
cyclohexanone ethylene ketal as a model reaction to research
the acid catalytic activity of 1. With single factor level analysis,
we obtained the optimum reaction conditions of yields of
ketals: reaction time were 3.0 hours, cyclohexanone/glycol
molar ratio is 1 : 1.5, the amount of acid catalyst 1 was 0.1 g,
the most suitable volume of water-carrying agent cyclohexane
was 16 mL, reaction temperature was allowed to reux at 100–
105 ꢁC (Fig. 5). Under the optimum experimental conditions,
the yield of cyclohexanone ketal was 95%. The ketal product was
characterized by FT-IR (Fig. S13, ESI†) and PXRD (Fig. S14,
ESI†). Aer 1 h of reaction, the catalyst was removed through
hot ltration and the ltrate was further heated for 2 h at
100 ꢁC. No further growth of the conversion (Fig. 5e) indicated
Fig. 3 The diffuse reflectance UV-vis-NIR spectrum of (Fhn)0.5 vs.
energy (eV) for 1. F ¼ (1 ꢀ R) ꢂ (1 ꢀ R)/2R; A ¼ log 1/R.
gives a direct transition (n ¼ 1/2) at 2.34 eV (Fig. 3). The results
demonstrate the semiconductor nature for 1.
Magnetic property
The temperature dependence of magnetic susceptibility of 1
was investigated at 2–300 K in an applied magnetic eld of 1000
Oe. The cM versus T plot demonstrated the cM value slowly
increases from 0.0071 emu molꢀ1 at 300 K to 0.045 emu molꢀ1
at 26 K, and then exponentially reaches the maximum value of
0.47 emu molꢀ1 at 2 K. The cMT value of 1 is 2.13 emu K molꢀ1
at 300 K (Fig. 4), which is larger than the theoretical value of
1.125 emu K molꢀ1 expected from three isolated Cu2+ (S ¼ 0.5, g
¼ 2.0). As the temperature is lowered, the cMT value decreases
slowly up to 50 K and then sharply falls to a minimum value of
0.94 emu K molꢀ1 at 2 K. The temperature dependences of cM
and cMT versus T plots for 1 suggest the presence of antiferrꢀo1-
magnetic coupling interactions between Cu2+ centers. The cM
versus T plot follows the Curie–Weiss law with C ¼ 3.56 emu K
molꢀ1 and q ¼ ꢀ29.97 K in the range of 48–300 K (Fig. S12,
ESI†), which further demonstrated the presence of antiferro-
magnetic interactions between Cu2+ ions in 1. The result was
Fig. 5 (a) Effect of the amount of 1 on the yield of cyclohexanone
ethylene ketal. (b) Effect of molar ratio of glycol and cyclohexanone on
the conversion of cyclohexanone ethylene ketal. (c) Effect of the
volume of cyclohexane on the yield of cyclohexanone. (d) Effect of
reaction time on the yield of cyclohexanone ethylene ketal. (e)
Conversion of cyclohexanone ethylene ketal versus time curves with 1
as catalyst at 100 ꢁC and catalyst was removed from the suspension
Fig. 4 The plots of cM and cMT vs. T in the temperature of 2–300 K for after 1 h. (f) The recycle experiments of 1 for the catalytic synthesis of
1.
cyclohexanone ethylene ketal.
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that 1 was a heterogeneous catalyst in the catalytic reaction and
was not dissolved in the reaction system. 1 was recovered by
centrifugation aer 3 h of reaction. The catalyst could be reused
for at least 5 times, without signicant loss of catalytic activity
(Fig. 5f). Additionally, as exhibited in Table 1, compound 1
showed better catalytic activity than the parent materials
K3Mo5O17H and Cu3(trz)3(OH)3(H2O)4, in the presence of which
the yield of cyclohexanone ethylene ketal were 95%, 44% and
36%, respectively (Table 1). The reaction mechanism of the
condensation of cyclohexanone and glycol catalyzed by 1 was
Lewis acid active sites, which come from unsaturated coordi-
nation sites of Cu centers attack on the carbonyl carbon forming
C+ ion, and then C+ ion accepts the attack of nucleophile glycol
forming ketals (Fig. S15†).
Photocatalysis property
POMs-based coordination polymer was introduced transition
metal and organic ligand as functional groups, which could
enrich the potential applications of POMs, such as catalysis and
conductivity. Some POMs-based coordination polymers have
been proven to be an excellent kind of green and cheap pho-
tocatalyst and can be used to photodecomposition of organic
dyes.13 Liu et al.13a synthesized a POMs-based coordination
polymer
[WO4Ni(en)2(H2O)}3][Ni(en)3]{P2W18O62}$[Ni(en)3]
CO3$H2O (en ¼ ethanediamine), which achieved 97% degra-
dation rate for the photocatalytic degradation of methylene blue
(MB) under visible light irradiation. Luo et al.13b reported
a POMs-based coordination polymer {Cu2(L)2[CrMo6(OH)5-
O19](H2O)2}$2H2O (L ¼ N,N0-bis(3-pyridinecarboxamide)-1,3-
propane), which exhibited photocatalytic activity on the
photodecomposition of RhB under visible light with 97.6%
degradation rate. Herein, we investigated the photodecompo-
sition activity of 1 for RhB. We chose visible light as the light
source, because the calculated HOMO–LUMO gap (Eg) of
compound 1 was 2.34 eV, which corresponds to visible light
absorption. The UV-vis diffuse reectance spectrum of 1 was
presented in Fig. 3 and S11, ESI.†
Fig. 6 (a) Absorption spectra of RhB in the presence of 1 under visible
light irradiation. (b) Plots of degradation rate versus irradiation time
under visible light in the presence of 1, (TBA)3[Mo5O17H], Cu3(trz)3(-
OH)3(H2O)4 and no catalyst, respectively. (c) The recycle experiments
of 1 for the photodecomposition of RhB.
The photodegradation rate of RhB by 1 was 98% in 200 min.
Aer reuse ve times, the result did not change evidently
(Fig. 6a and c). For a comparative purpose, the photodecom-
position rate in the presence of (TBA)3[Mo5O17H], Cu3(trz)3(-
OH)3(H2O)4 and blank were also measured, respectively. We
could nd that photodecomposition rates of RhB by (TBA)3[-
Mo5O17H], Cu3(trz)3(OH)3(H2O)4 and blank were only 37%, 13%
and 8% respectively(Fig. 6b), which were much lower than that
by 1.
Table 1 Catalytic performances of 1 compared with the reference
catalysts for the synthesis of cyclohexanone ethylene ketala
We proposed that the photodegradation of RhB by 1 was
6ꢀ
realized by the synergy effect of Cu3(trz)3(OH)32+ and Mo5O18
units of 1. The maximum absorbance wavelength of UV-vis
diffuse reectance spectrum of (TBA)3[Mo5O17H] and Cu3(-
trz)3(OH)3(H2O)4 were 280 nm and 520 nm, respectively (Fig. S9
Entry
Catalyst
Time/h
Yield/%
2+
and b, ESI†). Therefore, Cu3(trz)3(OH)3 acts as sensitizer
1
2
3
K3HMo5O17
Cu3(trz)3(OH)3(H2O)4
Compound 1
3
3
3
44
36
95
absorbing visible light to produce photo-introduced electron.
The photo-introduced electron is transferred to the lower LUMO
orbit of Mo5O186ꢀ and then combined with O2 in air generated
O2ꢀc radical, which acts as oxidizing agent to effectively attack
and oxidize RhB molecule. The proposed mechanism was
showed in Fig. 7.
a
Reaction conditions: the molar ratio of cyclohexanone to glycol was
1 : 1.5; water-carrying agent: 16 mL of cyclohexane; reaction
temperature: 100–105 ꢁC; the molar ratio of the catalyst was 0.06 mmol.
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Fig. 7 The proposed mechanism for the photodegradation of RhB
by 1.
Conclusions
In summary, a new 3D coordination polymer built by triangle
trinuclear copper units and triazole with [Mo5O18]
6ꢀ anions as
templates were successfully synthesized. Its catalytic activities
in the synthesis of cyclohexanone ethylene ketal and visible
light photodegradation of RhB were explored. It exhibits good
Lewis acid catalytic activity for the synthesis of cyclohexanone
ethylene ketal with 95% conversion aer 3 h. Its forbidden
bandwidth belongs to the semiconductor category, and it can
catalyze the photodecomposition of RhB under visible-light
with above 98% degradation rate, demonstrating it is an
effective catalyst for the removal of organic pollutant under
visible light. This work demonstrates that it is a feasible way to
achieve POMs-based coordination polymer with excellent
catalytic performance by combining catalytic active building
blocks. To some degree, this may offer an access to obtain
a series of POMs-based catalysts bearing attractive catalytic
activities. This continuous research is currently going on in
our group.
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Conflicts of interest
There are no conicts to declare.
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Acknowledgements
This work was supported by the National Natural Science
Foundation of China (Grants 91622108, 21371029, 21671033,
and 21571030) and the Open Research Fund of the State Key
Laboratory of Inorganic Synthesis and Preparative Chemistry
(Jilin University, Grant 2015–01).
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