Synthesis And Photocatalytic Apllication Of Bismuth Oxyhalide/Metal-Organic Frameworks Composite

Many organic pollutants in water especial for dye and antibiotics,are difficult to degrade and easy to accumulate,which seriously threaten human health and ecological security.Semiconductor photocatalysis has showed great potential in treating organic pollutants in water for its features of mild conditions,low energy consumption and high efficiency.However,commonly used single semiconductors are low-efficient and cannot satisfy the requirements for practical application.The development of higher-performance photocatalysts has attracted great interest.Bismuth Oxyhalide is a kind of commonly used semiconductor with high chemical stability and excellent photocatalytic activity.Metal-Organic Frameworks（MOFs）is a kind of functional inorganic-organic hybrid material with huge specie surface areas.Constructing appropriate heterojunction is one of the effective ways to improve the photocatalytic performance of semiconductors.Thus,combination of the two materials is expected to build appropriate heterojunction for the effectively removal of organic pollutants from water.In this paper,two kinds of novel BiOX/MOFs composite photocatalysts were synthesized via appropriate preparation methods.The characterizations of the as-prepared samples were performed by X-ray diffraction,scanning electron microscopy,Fourier transform infrared spectroscope and other instruments.Rhodamine B（Rh B）and norfloxacin（NOR）were selected as target pollutants to evaluate the photocatalytic performance of the two kinds of composites,respectively.The stability of composites was investigated by recycle experiment and characterization.In addition,we proposed the possible reasons for the enhanced photocatalytic performance and photodegradation mechanism by analyzing the results of optical characterization and radical trapping experiment.The main conclusions are as follows:As for the commonly used dye Rh B,we successfully synthesized BiOCl/UiO-66composite photocatalyst.Compared with pristine materials and mechanically mixed sample,the composite exhibited the higher photodegradation performance of Rh B under ultraviolet and visible light irradiation.The degradation efficiency of Rh B（15 mg/L）over BiOCl/UiO-66 was 97.34%after the 120 min irradiation of visible light.BiOCl/UiO-66exhibited good structural stability.The mechanism of Rh B degradation under visible light proceeded via a photosensitization process.A better absorptivity and effective electron transfer within the hybrid material might be responsible for the enhanced photocatalytic performance.As for the commonly used antibiotics NOR,we successfully synthesized a series of BiOBr/UiO-66-NH₂ composites.The composites with different proprotions all exhibited higher NOR removal performance than the pure components and mechanically mixed sample under simulated sunlight.Among them,the composite with UiO-66-NH₂content of 20%（BUN-20）,had good structural stability and the best performance on the removal of NOR.The removal efficiency of NOR（10 mg/L）over BUN-20 was 93.60%after the 180 min irradiation of simulated sunlight.Increased surface active sites,improved light absorption ability and lower recombination probability of electron-hole pair might be responsible for the enhanced photocatalytic performance.This study might not only provide theoretical basis for designing a novel composite photocatalyst in future,but also expand the application of MOFs in photodegrading organic pollutants and offer the guidelines for BiOX modification by using MOFs.