Photocatalytic Properties Of NH₂-MIL-125（Ti） Composites Prepared By Wmulsification

Photocatalysis technology has the advantages of low energy consumption,simple and mild reaction conditions,and is widely used in the degradation of Cr（Ⅵ）and formaldehyde.Photocatalysts are an important part of photocatalysis research.Metal-organic frameworks（MOFs）have the characteristics of high specific surface area,high pore volume,and flexibility and tailorability,making them one of the ideal supports for constructing photocatalytic systems.NH₂-MIL-125（Ti）is a typical Ti-MOF,but its application in photocatalysis is limited by its shortcomings such as easy recombination of photogenerated electron-hole pairs,large micropore transport resistance,and poor light absorption efficiency.Therefore,it is very meaningful to improve the photocatalytic performance of NH₂-MIL-125（Ti）.The emulsification method can change the optoelectronic properties of the material,and has the advantages of simplicity,controllability,high efficiency,easy separation and recyclability compared with the traditional stirring method.Based on this,this paper focuses on the emulsification method,and starts from the metal ion loading to modify NH₂-MIL-125（Ti）to prepare metal ion/NH₂-MIL-125（Ti）composite photocatalyst.Using XRD,SEM,XPS,BET,UV-vis DRS and other characterization methods to analyze the morphology and structure of the prepared composite photocatalyst,to explore the photocatalytic performance of the composite material,and to explore the influencing factors and repeatability of the photocatalytic process.The related mechanism was preliminary studied.The main contents and results are as follows:1.ZnCl₂/NH₂-MIL-125（Ti）and Cu Cl₂/NH₂-MIL-125（Ti）composite photocatalysts were successfully prepared by emulsification method,and Cr（Ⅵ）was photocatalytically reduced under UV and visible light conditions,respectively.The experimental results show that under UV light irradiation,the photocatalytic reduction of Cr（Ⅵ）by ZnCl₂/NH₂-MIL-125（Ti）can reach 95%within 150 min,and the reaction rate is 2.5 times and 3.8 times higher than that of NH₂-MIL-125（Ti）and math-ZnCl₂/NH₂-MIL-125（Ti）prepared by traditional mechanical stirring.After 5 cycles,75%of the photocatalytic reduction efficiency of Cr（Ⅵ）can still be retained,with good chemical stability.The best photocatalytic reduction efficiency of Cr（Ⅵ）was obtained when the loading of ZnCl₂was 1/6,pH=2,methanol was the hole scavenger and the addition amount was 0.5m L.Under visible light irradiation,Cu Cl₂/NH₂-MIL-125（Ti）can photocatalytic reduce Cr（Ⅵ）with 74%efficiency,and the reaction rate is 2.4 times and 6.4 times higher than that of NH₂-MIL-125（Ti）and math-Cu Cl₂/NH₂-MIL-125（Ti）.After three cycle experiments,the reduction efficiency can still reach 67%.The optimum conditions of the photocatalytic system were as follows:1/5 Cu Cl₂ loading,pH=2,EDTA-2Na as hole scavenger and 0.2m M as addition.2.NiCl₂/NH₂-MIL-125（Ti）composite photocatalyst was successfully prepared by emulsification with NH₂-MIL-125（Ti）as carrier.The photocatalytic oxidation rate of formaldehyde under visible light was 94%,which was 11.5 times and 8.9 times higher than that of NH₂-MIL-125（Ti）and math-NiCl₂/NH₂-MIL-125（Ti）.After four cycles,the photocatalytic oxidation efficiency of NiCl₂/NH₂-MIL-125（Ti）remained at 82%and had good stability.NiCl₂ and NH₂-MIL-125（Ti）were emulsified at the mass ratio of 1:4,the dosage of catalyst was 20 mg,the initial concentration of formaldehyde was 10 mg/L,and pH=7,NiCl₂/NH₂-MIL-125（Ti）had the best photocatalytic oxidation efficiency.