Synthesis,Structure And Catalysis Of Organic Inorganic Hybrid Materials Of Arsenomolybdate And Arsenotungstate

Polyoxometalates?POMs?containing arsenic as heteroatom is an important branch of heteropoly acid.Arsenic tungstate and arsenic molybdenum have reversible multi electron redox properties,certain photosensitivity polyoxometalates,and similar width of the band gap to TiO₂.Therefore,these materials are excellent catalysts,and have potential applications in electrocatalysis and photocatalysis.In this paper,six kinds of novel organic inorganic hybrids with arsenic as heteroatom were successfully synthesized by a one-step hydrothermal method using sodium arsenite with less toxicity as a source and bridging and modified effect of transition metal.According to the elemental composition analysis and single crystal X-ray diffraction results,the molecular formula:?H₂bpy?₂?Hbpy?[As W₁₁CoO₃₉]·H₂O?1?[Cu₇^Ibpy₇Cl₂(AsW₁₀^VIW₂^VO₄₀)]?2?[?Cu?bim?₂?₃(As₂W₁₈O₆₂)]?3?[(Cu₁₀pz₁₀Cl₄)(As₂W₁₈O₆₂)]?4?[?Cu?bpy?₂?₃(As^?As₂^?Mo₁₈O₆₂)]·8H₂O?5??bpy?₃[As^?As₂^?Mo₁₈O₅₉Cl₃]?6??bpy=4,4'-bipyridine?compound 1?2?6?,bpy=2,2'-bipyridine?compound 5?,pz=pyrazine,bim=2,2'-biimidazole?.The six compounds were characterized byIR,TG,XRD and UV-vis.The structural analysis shows that the compound 1 is the first single cobalt substituted one dimensional Keggin type tungstate compound.Compound 2 is a complex three-dimensional POMOF structure composed of a host metal organic layer and a Keggin type guest molecule,which is formed by Cu,bipyridine ligand and Cl-alternately.Compound 3 is a 6-connected 2-D Dawson-type arsenic tungstate.Compound 4 is a three-dimensional POMOF structure composed of 3-D metal organic network and Dawson guest molecule,which is formed by Cu,pyrazine and Cl-alternately.Compound 5 is the first six-connected 2-D arsenical molybdate layer with single arsenic cap.Compound6 is a novel single arsenic cap modified 0-D Dawson cluster substituted by the three chlorine.Compounds 1 and 2 have good electrocatalytic reduction effect on hydrogen peroxide and chlorate.Compounds 3 and 4 exhibit a double electrocatalytic behavior,which can catalyze the oxidation of inorganic substances such as hydrogen peroxide and chlorate,as well as catalyze the oxidation of redox biomolecules AA,which are potential dual functional sensor material.Compounds 5 and 6 have catalytic activity for the reduction of H₂O₂,Cl O₃^-,NO₂^-,etc.The different electrochemical behaviors of the six compounds are determined by the POMs species and the different structures.The compound 1-6 has photocatalytic activity for the degradation of typical azo dye methylene blue?MB?,Luo Danming B?RhB?and methyl orange?MO?under UV irradiation.The catalytic effect of two-dimensional layered molybdate modified by metal organic complex?compound 5?is much higher than that of zero dimensional homogeneous compounds,which indicates that the introduction of metal organic complex is beneficial to the electron transfer in the catalytic process.The mechanism of photocatalytic reaction was preliminarily explored by free radical trapping experiment with compound 5 as an example.The results showed that the reaction path of the three dyes was different.In addition,kinetic studies showed that the degradation process of three dyes was in accord with the first-order kinetic equation.