Preparation And Performance Study Of Defective Spindle-shaped NH₂-MIL-88B (Fe)-based Composite Photocatalys

With the acceleration of urbanization,it brings not only economic development but also serious environmental pollution and energy shortage.In particular,water pollution poses a serious threat to human health and natural environment,which has aroused widespread concern.In the past studies,photocatalysis has been regarded as a green and promising technology.It has been successfully used in water decomposition to produce hydrogen,CO2 reduction,NOx oxidation,degradation of organic pollutants,and Cr（VI）reduction.Metal-organic framework（MOFs）,as a new porous hybrid consisting of strong coordination bonds between organic bond groups and metal clusters,has the advantages of high adjustable characteristics and large specific surface area.Compared with traditional inorganic semiconductors,the function and structure of MOFs can be easily adjusted to the desired function and structure by modifying their metal centers or organic ligands,showing great advantages in photocatalysis.In this paper,the core-shell composite is formed by loading ZnIn₂S₄ nanosheets on the fusiform defective NH₂-MIL-88B（Fe）surface,which promoted the effective separation and migration of photogenerated electron hole pairs and improved the photocatalytic activity.In this paper,the preparation,characterization,photocatalytic performance test and possible photocatalytic mechanism of defective NH₂-MIL-88B（Fe）and its composites are investigated comprehensively and deeply.The contents are as follows:（1）Fusiform NH₂-MIL-88B（Fe）is prepared by a simple solvothermal method,and two defective NH₂-MIL-88B（Fe）are prepared by doping different organic ligands（pyrrole,pyrrole-2-carboxylic acid）.The photocatalytic properties of bisphenol A（BPA）and ofloxacin（OFL）are tested by comparing the photoabsorption capacity of the original NH₂-MIL-88B（Fe）and NH₂-MIL-88B（Fe）samples with ligand defects.It is found that NH₂-MIL-88B（Fe）with defects shows enhanced light absorption capacity and reduces band gap.Moreover,the photocatalytic degradation efficiency of NH₂-MIL-88B（Fe）doped with pyrrole-2-carboxylic acid is significantly improved,and the degradation efficiency of BPA increased from 38.1%to 48.6%,and the degradation efficiency of OFL increased from 37.5%to 51.8%within 180 min.After speculative analysis,the performance improvement may be due to the fact that the introduction of defects can generate the most ligand vacancies,provide sufficient active sites,and broaden the range of light absorption.（2）The defective NH₂-MIL-88B（Fe）@ZnIn₂S₄ core-shell heterojunction is synthesized by adding zinc chloride,thioacetamide and indium chloride tetrahydrate into the optimal solution of defective NH₂-MIL-88B（Fe）by oil bath method.In order to explore the optimal composite photocatalyst,the mass ratio of NH₂-MIL-88B（Fe）and ZnIn₂S₄ is adjusted.A series of characterization analyses are carried out on two single samples and all composites,as well as photocatalytic degradation of BPA and OFL,and photocatalytic hydrogen production to test the photocatalytic performance of the samples.The results show that the defective NH₂-MIL-88B（Fe）@ZnIn₂S₄-3 sample shows the best performance,removing～99.4%BPA and～98.5%OFL within 180 min,and the hydrogen production reached 502 μmol g^-1h^-1.The constructed composite system has a wide application prospect in the field of environmental remediation and energy,and also provides a new idea for exploring efficient photocatalysts.