Wei-Chao Chen

Assembly of organic–inorganic hybrid materials constructed from polyoxometalate and metal–1,2,4-triazole units: synthesis, structures, magnetic, electrochemical and photocatalytic properties

A series of organic–inorganic hybrid compounds built from Keggin and Wells–Dawson polyoxometalates and TM-trz complexes (Htrz = 1,2,4-triazole) were obtained at different pH values under hydrothermal conditions, namely, [Co2(H2O)2(Htrz)5][SiW12O40]·2.5H2O (1), [Zn5(Htrz)8(trz)2(H2O)8][SiW12O40]2·10H2O (2), [CuI2CuII4(Htrz)4(trz)4Cl2][GeW12O40]·15H2O (3), [CuI2CuII4(Htrz)4(trz)4Cl2][SiW12O40]·15H2O (4), K2Na2(H2O)2[Co11(trz)14(H2O)14][P2W18O62]2·29H2O (5) and [Cu12(trz)10(Htrz)2(OH)4(SO4)2(H2O)6][P2W18O62]·28H2O (6). All of the compounds were characterized using single-crystal X-ray diffraction, TG analysis and powder X-ray diffraction. Compound 1 contains a kind of bimetallic–organic segment [Co2(Htrz)5]4+, which could be regarded as a quasi-sinusoid-like chain. 2 is a dimer constructed from two [SiW12O40]4− units linked by a [Zn5(trz)2(Htrz)8]8+ motif. In 3 and 4, the 2D wall-like layers constructed by the Cu(II) ions and Htrz ligands are extended into 3D frameworks by polyanions. 5 shows a complicated three-dimensional (3D) framework with a {412·612·84}{46}2 topology. Compound 6 is also a complicated 3D structure based on a triangular trinuclear Cu-trz unit and [P2W18O62] polyanions. To the best of our knowledge, 6 represents the largest copper cluster linked by amines in a POM system. Structural diversities reveal that the pH value of the reaction system plays a crucial role in the assembly of POM-based hybrids. Moreover, the optical band gaps, electrochemical properties, magnetic properties and the photocatalytic properties of the compounds have been investigated.

Assembly of Cerium(III)-Stabilized Polyoxotungstate Nanoclusters with SeO32−/TeO32− Templates: From Single Polyoxoanions to Inorganic Hollow Spheres in Dilute Solution

A versatile one-pot strategy was employed to synthesize three cerium(III)-stabilized polyoxotungstates nanoclusters by combining cerium linkers and SeO3(2-)/TeO3(2-) heteroanion templates: K32Na16[{(XO3)W10O34}8{Ce8(H2O)20}(WO2)4(W4O12)]·nH2O [X=Se, n=81 (1); X=Te, n=114 (2)] and K12Na22[{(SeO3)W10O34}8{Ce8(H2O)20}(WO2)4{(W4O6)Ce4(H2O)14(SeO3)4(NO3)2}]· 79H2O (3), which are the first lanthanide-containing polyoxotungstates with selenium or tellurium heteroatoms. The three clusters were characterized by single-crystal X-ray structure analysis, IR spectroscopy, thermogravimetric/differential thermal analysis, UV/Vis spectroscopy, ESI-MS, and X-ray photoelectron spectroscopy. Their electrochemical, photoluminescence, and magnetic properties were investigated. Their behavior in solution was studied by transmission electron microscopy, which showed that their single polyoxoanions assemble into intact, uniform-sized, purely inorganic hollow spheres in dilute water/acetone solution.

pH-controlled and sulfite anion-directed assembly of a family of cerium(III)-containing polyoxotungstates clusters.

A versatile one-pot strategy was employed to synthesize five cerium(III)-containing polyoxotungstate nanoclusters through pH-controlled and sulfite anion-directed assembly: [C2H8N]3Na7[Ce2(H2O)6W22O72(OH)4]·20H2O (1) at pH 5.0; [C2H8N]8Na16[Ce4(H2O)12W44O144(OH)12]·23H2O (2) at pH 4.5; [C2H8N]2Na4Ce2[Ce2(H2O)10W28O92(OH)2]·27H2O (3) at pH 2.8-3.3; [C2H8N]2Na7[{α-SW7O28}{Ce2(H2O)6}(W3O6){α-SW9O32}{α-SW9O31(OH)}]·18H2O (4) at pH 2.5; [C2H8N]2Na18[Ce2(H2O)9W36O110(OH)12]2·30H2O (5) at pH 1.5. These compounds were characterized by single-crystal X-ray structure analysis, IR spectroscopy, thermogravimetric (TG) analysis, X-ray photoelectron spectroscopy (XPS), and electrospray ionization mass spectrometry (ESI-MS). Moreover, their electrochemical properties were investigated. Single-crystal X-ray structure analysis revealed that 1 and 2 were di- and tetra-cerium(III)-bridged polyoxotungstates, constructed from two different types of lacunary {W11} units. 3 composed of the well-known cerium(III)-stabilized {W28} unit and organic amine-sodium-cerium cations, was isolated in the pH range 2.8-3.3. In this reaction system, the SO3(2-) anion acted as a heteroanion template at a lower pH 2.5. 4 was isolated by the combination of cerium(III) centers and SO3(2-) heteroanion template, which is the first lanthanide-containing polyoxotungstates with sulfur heteroatoms, and the 4f metal cerium(III) centers in 4 both have eight-coordinated modes and the SO3(2-) heteroanion templates display μ7 and μ9 coordination modes. At a much lower pH 1.5, the polyanion of 5 was obtained, two triangular-shaped {W36} subunits were bridged by the cerium(III) ions, resulting in the largest lanthanide-containing iso-polyoxotungstates known to date.

A Stable Polyoxometalate‐Pillared Metal–Organic Framework for Proton‐Conducting and Colorimetric Biosensing

A stable metal-organic framework pillared by Keggin-type polyoxometalate, Cu6 (Trz)10 (H2O)4 [H2 SiW12 O40 ]⋅8 H2O (Trz=1,2,4-triazole) (1), has been prepared under hydrothermal condition. The 2D layer structure with a 22-member ring was formed by Cu(2+) ions, which are connected with each other via the Trz ligands on the ab plane. Thus, the 2D layers are further interconnected through Keggin polyoxoanions to generate a 3D porous network with a small 1D channel. Moreover, the presence of polyoxoanions make it exhibit selective adsorption of water and proton-conducting properties. Additionally it showed efficient intrinsic peroxidase-like activity, providing a simple and sensitive colorimetric assay to detect H2O2 .

Oxidative Polyoxometalates Modified Graphitic Carbon Nitride for Visible-Light CO2 Reduction

Developing a photocatalysis system for converting CO2 to valuable fuels or chemicals is a promising strategy to address global warming and fossil fuel consumption. Exploring photocatalysts with high-performance and low-cost has been two ultimate goals toward photoreduction of CO2. Herein, noble-metal-free polyoxometalates (Co4) with oxidative ability was first introduced into g-C3N4 resulted in inexpensive hybrid materials (Co4@g-C3N4) with staggered band alignment. The staggered composited materials show a higher activity of CO2 reduction than bare g-C3N4. An optimized Co4@g-C3N4 hybrid sample exhibited a high yield (107 μmol g-1 h-1) under visible-light irradiation (λ ≥ 420 nm), meanwhile maintaining high selectivity for CO production (94%). After 10 h of irradiation, the production of CO reached 896 μmol g-1. Mechanistic studies revealed the introduction of Co4 not only facilitate the charge transfer of g-C3N4 but greatly increased the surface catalytic oxidative ability. This work creatively combined g-C3N4 with oxidative polyoxometalates which provide novel insights into the design of low-cost photocatalytic materials for CO2 reduction.

Trimeric hexa-dimethyltin-functionalized selenotungstate [{Sn(CH3)2(CH3COO)}3{Sn(CH3)2}3{Se2W18O62(OH)(H2O)}3]18−

The trimeric organic–inorganic hybrid selenotungstate(IV) [{Sn(CH3)2(CH3COO)}3{Sn(CH3)2}3{Se2W18O62(OH)(H2O)}3]18− is composed of three Wells–Dawson-type {α-Se2W18} fragments and six {(CH3)2Sn2+} groups involving the first reported carboxyl-modified dimethyltin moieties, exhibiting photocatalytic H2 evolution activity.

Assembly of Large Purely Inorganic Ce-Stabilized/Bridged Selenotungstates: From Nanoclusters to Layers

A versatile one-pot strategy was used to synthesize two large, purely inorganic selenotungstates, nanocluster K(6)Na(16) [Ce(6)Se(6)W(67)O(230) (OH)(6) (H(2)O)(17)]⋅47 H(2)O (1) and layer K(9)Na(5) Ce(H(2)O)(4) [Ce(6)Se(10)W(51)O(187) (OH)(7) (H(2)O)(18)]⋅45H(2)O(2), by combining cerium centers and SeO(3) (2-) heteroanion templates. Compound 1 displays a Ce-stabilized hexameric nanocluster with one rhombus-like {W(4)O(15) (OH)(3)} unit in the center, whereas compound 2 is the first example of a Ce-bridged layer selenotungstate network based on linkage of the unusual {Ce(6)Se(10)W(51)O(187) (OH)(7) (H(2)O)(18)} clusters and additional Ce(H(2)O)(4) fragments via Ce-O-Se bridges. The compounds were characterized by elemental analyses, IR spectroscopy, thermogravimetric analyses, powder and single-crystal X-ray diffraction, and electrospray ionization mass spectrometry. Moreover, the electrochemical property of compound 1 was also investigated.

An unprecedented 3D architecture based on a Nb/W mixed-addendum polyoxometalate and lanthanide–organic complex: synthesis, crystal structure and properties

For the first time, an unprecedented 3D framework based on lanthanide-containing Nb/W mixed-addendum polyoxometalate [H3La8(H2O)32(C6H5NO2)6][SiW9Nb3O40]3·8H2O (1) has been obtained by utilizing the steam-assisted conversion method. Meanwhile, the stability, electrochemical behavior, and photoluminescence properties of 1 have also been discussed.