Preparation And Photocatalytic Properties Of TiO₂/Metal-Organic Frameworks Composite Materials

The photocatalytic technology of semiconductor materials is applied to the field of pollutant degradation,CO2 reduction,solar cell and organic synthesis,which is considered as an ideal way to solve the energy crisis and environmental problems.Among various semiconductor photocatalysts,titanium dioxide(TiO2)is considered as the most ideal photocatalytic material due to its advantages of good stability,high catalytic activity,green non-pollution,simple preparation and low cost.However,high band gap energy,narrow light response range and low quantum utilization limit the practical application of TiO2.Therefore,the modification of TiO2 is one of the current researches focuses.The formation of heterostructure with other materials is one of the effective means to improve the photocatalytic performance of TiO2.Meta-organic frameworks(MOFs)have been demonstrated a wide promising application in molecular recognition,gas separation,catalysis,and drug delivery due to their high surface area,large poresize,tunability,well-defined nanometer-scale cavity and chemical tailor-ability.MOFs materials with high specific surface area and good adsorption performance combined with high activity semiconductor photocatalysts to form composite photocatalysts,which provides a promising strategy for the preparation of new photocatalysts.In this paper,the photocatalytic activity of TiO2 was enhanced by combining TiO2 with MOFs to form new photocatalytic materials.The specific research contents are as follows:(1)The design and fabrication of Ti02/ZIF-8 hybrid photocatalyst.ZIF-8 with large specific surface area,good thermal and chemical stability is selected as a typical MOFs material.The new hybrid TiO2/ZIF-8 nanobeads are produced by decorating the surface of as-synthesized mesoporous TiO2 spheres with ZIF-8 nanoparticles.At 300 mW·cm-2 light irradiation,the removal rate of Cr(?)of TiO2/ZIF-8 reached 99%after 60 min,which was significantly higher than 80%of TiO2.The results show that the enhancement of photocatalytic performance of TiO2/ZIF-8 spheres is based on the strong ability of adsorping Cr(?)by ZIF-8 spheres and the more effective charge transfer in the composites.(2)The design and fabrication of TiO2/MIL-101(Cr)hybrid photocatalyst.MIL-101(Cr)with high stability and excellent CO2 adsorption performance was selected as a typical MOFs material.TiO2/MIL-101(Cr)core-shell composites were successfully prepared by adjusting TiO2 reactant content and reaction temperature.TiO2/MIL-101(Cr)composite has a high specific surface area,which can provide more active sites and high CO2 adsorption performance.After 6 hours of light irradiation,the CH4 yield of TiO2/MIL-101(Cr)reached 1.29 mol·g-1,about 1.4 times that of pure TiO2.The rate of CH4 generation over the TiO2/MIL-101(Cr)hybrid photocatalyst could be significantly enhanced by loading of Pt as a cocatalyst to improve the separation of the photogenerated electron-hole pairs,which was about 13 times higher than that of pure TiO2/MIL-101(Cr).