Preparation And Properties Of Metal Organic Frameworks/Inorganic Semiconductor Composites

In recent years,photocatalytic technology is regarded as an important way to control pollution and relieve energy shortage due to its simple operation,low energy consumption and wide application range.Among many photocatalytic materials,metal-organic frameworks（MOFs）is expected to be used as photocatalyst for the degradation of organic pollutants because of its large specific surface area and high porosity.Among them,the Zr-based metal organic frameworks UiO-66 has attracted extensive attention due to its photocatalytic performance and preparing in large scale.Furthermore,the composite photocatalyst consisting of UiO-66 and inorganic semiconductors can be explored for utilizing their advantages and performances on photocatalysis,becoming a research hotspot of functional materials.This thesis aims to enhance the photocatalytic activity of UiO-66 and prepare a composite photocatalyst with excellent photocatalytic performance through effective synthesis method.Therefore,this study concerns on the preparation methods of UiO-66/sulfide copper composites and the according optical properties and performances on photodegradation of organic dyes.The main research work are as follows:（1）Preparation and photocatalytic performance of the CuS/UiO-66 composites:the CuS/UiO-66 composites were prepared by the solvothermal method.The series of as-prepared CuS/UiO-66 composites with different CuS/UiO-66 mass ratios were determined by X-ray powder diffraction（XRD）and their composition was determined as hexagonal CuS and cubic Zr₆O₄（OH）₄（BDC）₆.By using scanning electron microscopy（SEM）,CuS was confirmed growing on the surface of UiO-66 nanoparticles to form a flower microsphere.The Ultraviolet-visible spectroscopy（UV-vis）showed that the absorption range of CuS/UiO-66composites was significantly broadened than that of pure UiO-66.The Photoluminescence spectrum（PL）showed that little of shift of the forbidden band gap after and before compositing,but lower strength of PL revealed the limitless of electron-hole recombination.Their photocatalytic performance on degradation of Rhodamine B（RhB）under visible light irradiation indicated that the CuS/UiO-66 composites exhibited a higher photocatalytic activity and stability than bare CuS or UiO-66.A possible photodegradation mechanism for the CuS/UiO-66 composites was proposed by analyzing the band gap of CuS and UiO-66.（2）Preparation and photocatalytic performance of the Cu_xS/UiO-66 composites:the Cu_x S/UiO-66 composites were prepared by the surface functionalization method,using3-mercaptopropionic acid as a surface-functionalizing agent.The series of as-prepared Cu_x S/UiO-66 composites with different Cu/Zr molar ratios were determined by X-ray powder diffraction（XRD）and their composition was determined as cubic Cu_xS and cubic Zr₆O₄（OH）₄（BDC）₆.The scanning electron microscopy（SEM）and transmission electron microscope（TEM）images illustrated that the Cu_xS nanoparticles were non-uniformly distributed on the surface of UiO-66 particles（100 nm）.By comparing the morphology of the composites prepared with and without MPA,it further demonstrated that the MPA played a surface-functionalized role in synthesis of UiO-66/Cu_xS composites.The Ultraviolet-visible spectroscopy（UV-vis）showed that the absorption range of Cu_xS/UiO-66 composites was broadened and covering the whole visible range.The Photoluminescence spectrum（PL）showed that the electron hole separation efficiency of the composite was obviously enhanced.The photocatalysis characterization of as-prepared Cu_xS/UiO-66 products showed that the composites had higher photocatalytic activity and stability than bare Cu_xS or UiO-66.The composites of UC-15 with the Cu/Zr molar ratio of 1.5 had the best performance on decomposing RhB under visible light irradiation,the degradation efficiency was 95%.And the UC-15 composites exhibited better photocatalytic activity than the mechanically mixed UC-15 composites,which indicated that there existed a potential synergistic effect between Cu_x S and UiO-66,making the composites had better adsorption performance and higher electron hole separation efficiency.In summary,the copper sulfide/UiO-66 composites have been successfully fabricated by the solvothermal method and surface functionalization method.The as-synthesized copper sulfide/UiO-66 composites exhibited excellent photocatalytic performance than bare copper sulfide and UiO-66.