Chunxiao Wang

High-efficiency photo- and electro-catalytic material based on a basket-like {Sr⊂P6Mo18O73} cage

A novel high-efficiency photo-/electro-catalyst based on phosphomolybdate (H4bth)[{Mn2(H2O)3} {Sr⊂P6Mo2VMo16VIO73}]·3H2O (1) (bth = 1,6-bis(triazole)hexane), has been hydrothermally synthesized and characterized by X-ray crystallographic analyses, FT-IR, UV-vis, TG-DTA, XRD, XPS, and the elemental analyses. Compound 1 is an eight-connected 2-D layer structure, which represents the highest-connected assembly of basket-type POMs. The compound exhibits universal high-efficient degradation ability for the azo dyes MB, RhB, and AP under UV and visible light irradiation. The catalyst has a long lifetime and can be recovered and reused with a slight loss of reactivity. The major photoreaction pathways of three dyes on the surface of catalyst 1 were detected by a series of radical trapping experiments. The result suggests that ˙O2−, ˙OH radicals and photogenerated h+ play different roles in the degradation process. The diffuse reflectivity spectrum provides essential evidences for the highly-efficient oxidation performance of basket-liked POMs. The compound also shows good bifunctional electrocatalytic behavior for oxidation of AA and reduction of NO2−.

Two unusual organic–inorganic hybrid 3-D frameworks based on Keggin-type heteropoly blue anion-chains, 40-membered macrocycles, and sodium linker units

Two novel 3D compounds based on Keggin heteropoly blue anion-chains, [Na(H2O)2{MI(btp)}4(PWVI8WV4O39)] (M = Cu (1), Ag (2), btp = 1,3-bis(1,2,4-triazol-1-yl)propane), have been hydrothermally synthesized and characterized by elemental analysis, IR, TG, PXRD and single crystal X-ray diffraction. In compounds 1 and 2, the neighboring Keggin clusters are connected via sharing terminal oxygen atoms to form unusual Keggin anion chains by W–O–W covalent interactions, which are further reinforced by two copper(I) or silver(I) bridging fragments. Such saturated Keggin anion chains have been observed for the first time. The (Mbtp)4 40-membered cation-macrocycles and {Na(H2O)2} units serve as linkers to bond two adjacent anion chains resulting in infinite 2-D layers. The layers are further fused by interactions between the 40-membered macrocycles and {Na(H2O)2} units leading to intricate 3-D frameworks, which exhibit a novel 4, 6, 8-connected topology. In addition, compounds 1 and 2 exhibit good electrocatalytic activity for reduction of nitrite and fluorescence properties in the solid state at room temperature.

A 3-D supramolecular compound based on Keggin-type polyoxometalates and potassium-sulfanilamide

A Keggin-type polyoxometalate and potassium-sulfanilamide complex, [{K(C6H10N2O2S)2(H2O)}2(SiW12O40)2] · 2H3O+ · 10H2O (1), has been synthesized and characterized by elemental analyses, IR, TG, and single-crystal X-ray diffraction. Compound 1 exhibits infinite 1-D dimer chains which are constructed from Keggin units [α-SiW12O40]4− bridged by potassium-sulfanilamide fragments. These 1-D chains are linked via π–π interactions between benzene rings of the sulfanilamides to form 2-D layers, which are further packed into 3-D supramolecular assemblies through hydrogen bonds. The electrochemical and electrocatalytic behaviors of 1 have been studied in detail.

Two extended Wells–Dawson arsenomolybdate architectures directed by Na(I) and/or Cu(I) organic complex linkers

Two extended Wells–Dawson arsenomolybdates, (imi)2[{CuI(imi)2}2{Na(imi)2}{AsIIIAs2VMo18O62}]·2H2O (1) and {CuI0.5(trz)}6 [{CuI0.5(trz)}6(As2Mo18O62)] (2), (imi = iminazole; trz = 1,2,3-triazole), are hydrothermally synthesized and extensively characterized. Compounds 1 and 2 contain a fully oxidized Dawson {As2Mo18O62}6− (abbreviated as {As2Mo18}) anion as the parent cluster unit. Compound 1 is a symmetric mono-arsenate capped anion cluster modified by two half occupancy {AsO3} units, which represents a new capping mode for Dawson clusters. The two adjacent mono-arsenate capped structures are linked by two {Na(imi)2} bridges to form a dimeric cluster, which, as a tetra-dentate ligand, further connects with adjacent dimers by four {Cu(imi)2} linkers to form an infinite ladder shaped chain. In compound 2, each classical Dawson cluster links six adjacent analogs by six {Cu0.5(trz)2} fragments forming an unprecedented 3D network via a unique belt-to-belt staggered pattern. This structure can be simplified as a 2,6-connected 3-D framework with {812·123}{8}3 topology. Compounds 1 and 2 represent the first 1-D and 3-D assemblies of Dawson-type arsenomolybdates, respectively. They display unique electrocatalytic behavior for the oxidation of ascorbic acid (AA) and reduction of NO2− as well as good photocatalytic properties for the degradation of the difficult-to-degrade dye AP under UV light.

1,4-Bis(imidazole)butane ligand and strontium(II) directed 1-D chains based on basket-type molybdophosphates and transition metal (TM) linkers

Five unclassical heteropoly blues, (H2bib)3[{TMII(H2O)2}{Sr⊂P6Mo2VMo16VIO73}]·nH2O (TM = Fe (1), Co (2), Ni (3), Cu (4), Zn (5)); bib = 1,4-bis(imidazole)butane), have been hydrothermally synthesized and fully characterized. Compounds 1–5 are based on the basket-shaped [Sr⊂P6Mo2VMo16VIO73]8− (abbreviated as {P6Mo18O73}) units, which consist of a vacant Dawson-type “basket body” {P2Mo14} unit and a “handle”-like {P4Mo4} fragment encasing a Sr2+ cation in the central cage. All the compounds exhibit isostructural 1-D zigzag chains linked by a {TM(H2O)2} unit, which are observed for the first time as 1-D basket-like assemblies connected by a TM linker. The optical band gaps of 1–5 show that they are semiconductor materials and potential photocatalysts. Compound 2 as a representative catalyst exhibits a universal highly efficient degradation ability for typical dyes MB, MO, and RhB under UV light and bifunctional electrocatalytic behavior for oxidation of AA and reduction of NO2−.

Construction of two novel borotungstates modified by different ligands connected with single/double bridges

Two novel organic–inorganic hybrid borotungstates are decorated by two disparate ligands: (H2bibp)2[bibp{Cu(bipy)(bibp)}2{Cu(bipy)Cl}2{BW12O40}2]·3H2O (1) and [{Cu(bipy)2}{Cu(bipy)(Hbtb)}{BW12O40}] (2) (bipy = 2,2′-bipyridine, bibp = 4,4′-bis(imidazolyl)biphenyl, btb = 1,4-bis(1H-1,2,4-triazol-1-yl)benzene) have been hydrothermally synthesized and structurally characterized by elemental analysis, IR, TG, UV-Vis, XRD and single-crystal X-ray diffraction. Compound 1 exhibits an interesting network consisting of two [BW12O40]5− ({BW12}) polyoxoanion units linked by two kinds of copper ions to shape a hole structure. Each unit is linked through [bibp{Cu(bipy)(bibp)}2{Cu(bipy)Cl}2]6+ to form a Z-type one-dimensional (1-D) chain by alternating the single/double-bridge connection. Compound 2 is composed of {BW12} polyoxoanions and the [{Cu(bipy)2}{Cu(bipy)(Hbtb)}]5+ coordination cation, connected by a {Cu-btb-Cu} single-bridge to generate a novel 1-D network. There are π–π stacking interactions or supramolecular interactions all throughout to construct two-dimensional (2-D) and three-dimensional (3-D) architectures. The photocatalytic properties, electrochemical properties and electrocatalytic activities of these two compounds have been investigated in detail.

Synthesis, crystal structure and properties of sandwich type compounds based on {AsW9} and a hexa-nuclear unit with three supporting TM–triazole complexes

Three hexa-nuclear substituted sandwich-type arsenotungstates, Na6[{Na(H2O)}3{Ni(Htaz)}3(AsW9O33)2]·4H2O (1), Na6[{Na(H2O)}3{Co(Htaz)}3(AsW9O33)2]·8H2O (2), and Na6[{Na(H2O)0.5}3{Mn(Htaz)}3(AsW9O33)2]·11H2O (3) (taz = 1,2,4-1H-triazole), have been synthesized and structurally characterized. Basic frameworks of 1–3 are constructed from sandwich-type [{Na(H2O)n}3{M(Htaz)}3(AsW9O33)2]6− (n = 1 or 0.5) anions and sodium cations. The transition metal ions M2+ and Na+ in the central belt are coordinated by α-[AsW9O33]9− units, taz, and water molecules to form {MO4(Htaz)} and {NaO4(H2O)m} (m = 1 or 2) segments in which M2+ ions are modified with Htaz ligands. These fragments connect alternately in an edge-sharing mode forming a six-membered ring. Such a triazole coordinated six-nuclear cluster is first observed in a sandwich-type arsenotungstate system. The compounds 1–3 exhibit good electrocatalytic activity to reduce hydrogen peroxide and antiferromagnetic interactions between the trinuclear M(II) clusters. In addition, complex 1 has a potent inhibition effect on cell proliferation of HeLa cells.

Self-assembly, bifunctional electrocatalytic behavior, and photocatalytic property of host–guest metal-oxide-based coordination polymers

Abstract A copper complex modified Mo-oxide hybrid network stabilized by Keggin polyoxoanion, [{Cu(bpy)2}{Mo12O34(bpy)12}][PMo12O40]2 (bpy = 2,2ʹ is-bipyridine) (1) has been synthesized via self-assembly of simple starting materials. In 1, six [MoO4(bpy)] complexes connect in two different corner-sharing modes to form triangles and linear trimer units, which interconnect alternately to form zigzag chains. {Cu(bpy)2} segments connect the chains into 2-D layers, which are further joined into 3-D supramolecular networks with 1-D channels. The {PMo12PO40} as guest molecules are incorporated into the channels. Compound 1 exhibits bifunctional electrocatalytic behavior for oxidation of ascorbic acid and reduction of H2O2, as well as high-efficient degradation ability for typical dye methylene blue under UV light.

Assembly of three supramolecular compounds based on [P2Mo5O23]6− and Ni(II) complexes

Three supramolecular compounds based on [P2Mo5O23]6− and Ni(II)–bim, [Ni(bim)3]3[P2Mo5O23]·2H2O (1), [Ni(Hbim)(bim)2]4[P2Mo5O23]2·3H2O (2), and [Ni(bim)(Hbim)(phen)]2[P2Mo5O23]·7H2O (3) (bim = 2,2′-biimidazole, phen = 1,10-phenanthroline), have been synthesized under hydrothermal conditions and characterized by elemental analysis, single-crystal X-ray diffraction, IR, and TG. All the compounds show 3-D supramolecular networks constructed from weak interactions among free Ni(II) complex, water, and oxygens of [P2Mo5O23]6−. Compound 3 represents the first supramolecular example integrating {Ni(bim)(Hbim)(phen)} with Strandberg-type phosphomolybdate. The compounds display good electrocatalytic activity to reduce hydrogen peroxide and intense fluorescence properties in solution at room temperature. Graphical Abstract Three 3-D supramolecular networks constructed from weak interactions among free Ni(II) complex, water molecule, and oxygen atoms of [P2Mo5O23]6− polyanions have been synthesized. The compounds display good electrocatalytic activity to reduce hydrogen peroxide and intensive fluorescent properties in the solution at room temperature.

Polyoxometalate Insertion into Cu–pz Porous and Cu-bim Knighthead Coordination Polymers: [{Cu4(pz)5.5}{Cu2(2,2'-bim)3}0.5{P2W18O62}]·H2O

The structure of crystallised {[Cu4(pz)5.5][Cu2(2,2′-bim)3]0.5[P2W18O62]}·H2O (1) (pz = pyrazine, bim = biimidazole) is reported. The crystal structure is characterised by cage-like pores [Cu8(pz)11]8+ of Cu ions linked through pz ligands. [P2W18O62]6– polyanions are capsulated into cage-like pores of [Cu8(pz)11]8+, forming ‘hamburger’-like units. Furthermore, the three-dimensional framework in 1 is achieved via copper-pyrazolate layers, binuclear copper-biimidazole subunits, and Dawson-type polyoxometalate clusters. The electrochemical properties of compound 1 were also studied in detail.