The Construction And Photocatalytic/Electrocatalytic Properties Of Functional Material Based On POM/MOFs

Polyoxometalates?POMs?have received extensive attention in the field of catalysis because of their good proton transfer ability,high protonic acidity and good thermal stability.However,due to the small specific surface area of POMs,its application in the field of catalysis is limited to some extent.Metal-organic framework materials?MOFs?are ideal carriers due to their structural diversity,modification,and large specific surface area and porosity.It has attractive application prospects in the fields of gas selective adsorption,separation,drug and catalysis.This paper is devoted to the preparation of polyacid-complexed POMOFs MOFs-derived metal sulfides by MOFs precursors.The application and stability of these materials in the field of photocatalysis are studied,including the following three parts:1.NH₂-MIL-101?Al?was synthesized by solvothermal method,and then two composite materials V10@NH₂-MIL-101?Al??1?and BiVO4@NH₂-MIL-101?Al??2?were successfully constructed by adding vanadium polyoxometalate to the reaction system of NH2-MIL-101?Al?.The materials were characterized by infrared spectroscopy?IR?,thermogravimetry?TG?,electron microscopy?SEM/TEM?and X-ray photoelectron spectroscopy?XPS?.Among them,material 2 showed high catalytic activity,selectivity and cycle stability in the reaction of photocatalytic oxidation of benzyl alcohol to benzaldehyde;In order to further prove the high catalytic activity of material 2,we performed photoelectrochemical characterization.The fluorescence spectroscopy indicated that material 2 has the strongest fluorescence intensity.The photocurrent and impedance spectra indicated that material 2 had the strongest photocurrent response and the minimum impedance.These results indicate that the material 2 can effectively inhibit the recombination of photogenerated electrons and holes,thereby exhibiting high catalytic activity;3.Firstly,two new bimetallic organic framework compounds,Cd/Co-MOF?3?and Cd/Ni-MOF?4?,were synthesized by solvothermal method.Then,two kinds of CdS-Co9S8?5?and CdS-NiS2?6?mixed metal sulfides with heterojunction structure were prepared by high temperature vulcanization treatment of these two bimetallic MOF precursors.The materials were characterized by powder XRD,EDX and XPS.Among them,5 and 6 can efficiently oxidize benzyl alcohol to benzaldehyde while high-efficiency photocatalytic hydrogen production,and still maintain good catalytic activity after 4 cycles.We determined the conversion of benzyl alcohol and the selectivity of benzaldehyde by high performance liquid chromatography and nuclear magnetic resonance spectroscopy.Further,the isotope labeling experiments confirmed that the hydrogen produced was derived from solvent water.Then,XPS and photoelectrochemical characterization were carried out by using material 5 as an example.XPS characterization of pure Co9S8 and material 5 showed strong interaction between CdS and Co9S8 in material 5;Further,time-resolved fluorescence and fluorescence spectra were obtained.It indicates that material 5 has shorter fluorescence lifetime and weaker fluorescence intensity than pure CdS,indicating that material 5 can effectively promote the separation of photogenerated electrons and holes;Then,the photocurrent and electrochemical impedance characterization indicate that material 5 has the strongest photocurrent response and minimum impedance than pure CdS and pure Co9S8,which further indicates that material 5 can effectively inhibit the recombination of photogenerated electrons and holes,thus exhibiting high catalytic activity.