Study On Preparation And Catalysis Of Composite Materials Based On POMs Building Unit

Polyoxometalates（POMs）anions are nanoclusters of transition metal oxides containing a large amount of oxygen on the surface.Due to stable structure and potential practical value,POMs have attracted extensive attention in many fields.The hourglass molybdenum-phosphate complex composed of two[P₄Mo₆^VO₃₁]^12-（{P₄Mo₆}）half units linked by transition metal ions is a fully reduced cluster,which attracts great interest.The fully reduced structure{P₄Mo₆}with rich oxygen atoms provides more coordination sites for the polyacid-based crystal structure.In addition,Mo atoms in{P₄Mo₆}structure are all in+5 valence state and have redox properties.In this paper,a ligand was selected to synthesize five novel hybrid materials with POMs and different transition metal ions.The properties of electrocatalysis,proton conduction and electrochemical sensing of materials were studied.1.A kind of{P₄Mo₆}based hybrid material（H₂L）₃[Zn₃(H₆P₄Mo₆O₃₁)₂]（CUST-571,L=1,4-bis[（1H-imidazole-1-yl）methyl]benzene）was synthesized.At 85°C and 98%relative humidity（RH）,the proton conductivity of CUST-571 is 4.54×10^-3 S cm^-1,which was also due to the continuous proton transport way provided by the N-containing ligand.In addition,this study also proved that CUST-571 has a good catalytic decomposition performance of H₂O₂,which is beneficial to improve the life of fuel cells.2.Two{P₄Mo₆}based crystalline materials（H₂L）₂[Co₃(P₄Mo₆O₃₁)₂]·5H₂O（CUST-572）and[Mn(P₄Mo₆O₃₂)]·5H₂O（CUST-573）with metal center modification were synthesized by hydrothermal reaction,which can be used as high efficient catalyst for electrochemical detection of ultra-trace Cr（VI）.The{P₄Mo₆}metal cluster has synergistic effect with different transition metal centers,and has electrochemical detection performance,high selectivity and good chemical stability for Cr（VI）in electrolytes with a wide p H range.3.Two kinds of polyacid group hybrid materials （H₂L）₂[Fe₃(P₄Mo₆O₃₁)₂]·5H₂O（CUST-574）and（HL）₂HPO₄·（Mo O₃）₁₂（CUST-575）were prepared by one-step hydrothermal method.In the structure,the transition metal Fe atoms of CUST-574 coordinate with the O atoms on the surface of the polyacid cluster to form a two-dimensional polyacid framework.CUST-575 has no transition metal.Based on the characteristics of different polyacid clusters in the compound,the electrocatalytic effect of CUST-574 on the oxidizing substance NaNO₂ and reducing substance ascorbic acid（AA）is better than that of CUST-575.