Influence Of Bismuth Into The Preparation Of MIL-101(Fe) On Its Structure And Adsorption-photocatalytic Performance

To overcome the mass transfer resistance of micro-organic contaminants（MCs）in water and develop a knd of purification material that can efficiently remove MCs,in this study,Bi element was introduced to the preparation process of MIL-101（Fe）,and the BiOCl/MIL-101（Fe）with direct Z-scheme heterojunction and Bi-doped MOF material with excellent adsorption-photocatalytic properties were successfully prepared in situ by solvothermal method.When FeCl₃and Fe（NO₃）₃ were selected as the iron source,respectively,the effects of the introduction of different molar percentages of Bi on the structure and adsorption-photocatalytic performance were investigated by multiple representation methods and using rhodamine B（Rh B）,methylene blue（MB）and tetracycline as target pollutants.The experimental results show that when FeCl₃ was used as the iron source,the morphology of MOF changed from an octahedral structure to a fusiform structure with the increase of the introduction amount of Bi.When the introduction amount of Bi reached 35%-45%,BiOCl/MIL-101（Fe）composite could be prepared in situ,a heterojunction was formed between BiOCl and MIL-101（Fe）,the absorption edge of composite was redshifted and the light response range was expanded.The adsorption rate of BiOCl/MIL-101（Fe）to tetracycline reached 49.5%when the introduction amount of Bi was 45%,and the removal rate reached 81.8%after 180 minutes under visible light（Vis）irradiation,which was much higher than 33.1%of pristine MIL-101（Fe）and25.2%of pristine BiOCl.The photocatalytic apparent rate constant was 3.2 times that of MIL-101（Fe）and 4.9 times that of BiOCl.The removal rate of BiOCl/MIL-101（Fe）to tetracycline reached91.2%after 180 minutes under ultraviolet light（UV）irradiation.It also had similar adsorption-photocatalytic performance to Rh B.After 60 minutes under visible light irradiation,the removal rate of Rh B reached 86.5%,and the photocatalytic apparent rate constant was 3.1 times that of MIL-101（Fe）.When Fe（NO₃）₃ was used as the iron source,the introduction of a small amount of Bi was conducive to the crystallization of the sample,forming a slender fusiform structure and absorbing edge red shifting.When the introduction amount of Bi was 5%,the content of surface hydroxyl groups increased significantly,which was beneficial to accelerate the separation and transport of photogenerated electron-hole pairs,and promote the generation of hydroxyl radicals.The adsorption rate of Rh B reached 80.1%,and the removal rate reached 90.6%under visible light irradiation after 60 minutes,Rh B adsorbed on the surface could be effectively degraded.It also had excellent adsorption-photocatalytic activity for MB and tetracycline.The adsorption rate of tetracycline reached 68.9%,and the removal rate reached 90.8%after 180 minutes under visible light irradiation.Moreover,the by-products were also degraded.EIS,ESR and PL were used to explore the adsorption-photocatalytic mechanism of BiOCl/MIL-101（Fe）heterojunction and Bi-doped MOF materials prepared in situ.It was found that the BiOCl/MIL-101（Fe）composite prepared in situ could effectively promote the separation of photogenerated electron-hole pairs.·OH,·O₂^-and h⁺were all involved in the photocatalytic reaction,and·OH was the main active specie.The·OH and·O₂^-generated in the dark effectively promoted the adsorption of pollutants;the direct Z-scheme heterojunction formed could well explain the possible photocatalytic mechanism.The research findings will provide a new way for the development of adsorption-photocatalytic materials with simple preparation process,high efficiency,low cost and the ability of effectively overcoming the mass transfer resistance of MCs.