Performance Of MOFs/Bismuth-Based Semiconductors Heterojunctions For Photocatalytic Degradation Of Antibiotics

With the development of economy and the progress of science and technology,the environmental problems caused by antibiotics have become the focus of social concern.Photocatalytic technology has attracted wide attention because of its high reaction efficiency,mild reaction conditions,and good stability.Therefore,the development of photocatalysts with high solar energy utilization efficiency and long photogenerated carrier life is the core of the development of photocatalytic technology.Metal-organic frameworks（MOFs）have the following advantages as photocatalyst:（1）large specific surface area;（2）abundant active site;（3）adjustable structure.However,many MOFs have band gap values,which leads to the low utilization efficiency of visible light,which seriously limits its practical application.Bismuth-based semiconductors have attracted wide attention because of their rich compounds,nontoxicity,chemical inertness and rich reserves in China.However,bismuth-based semiconductors are prone to agglomeration during photocatalytic reactions,leading to catalyst inactivation.However,the combination of MOFs and bismuth-based semiconductors can not only increase the active site,enhance the utilization efficiency of visible light,inhibit photocarrier recombination,but also provide a platform for the dispersion and immobilization of bismuth-based semiconductors,and inhibit their agglomeration.Therefore,in this paper,we constructed a series of MOFs/bismuth-based semiconductors heterojunctions and explored the structure,morphology,optical properties and chemical composition of the heterojunctions through various characterization means.Sulfadiazine（SDZ）and enrofloxacin（ENR）were used to explore the degradation performance of heterojunction under visible light irradiation.The reaction mechanism was deeply explored through the detection of active substances,electrochemical test and density functional theory（DFT）calculation.Finally,the detoxification process of target pollutants was explored by analyzing the degradation pathway and intermediate toxicity.The main contents of this article are shown as follows:1.The UiO-66 with octahedral morphology was first prepared by the solvothermal method.A series of BiOI/UiO-66 heterojunctions were prepared via in-situ co-precipitation with the assistance of diethylene glycol.The results showed that after the introduction of BiOI,the visible light utilization efficiency of the photocatalyst was greatly improved and the separation of light electron-hole pair was effectively promoted,resulted in enhanced photocatalytic performance.BiU-9 has the best photocatalytic efficiency,which could degrade 99.8%of SDZ after 90 min under visible light irradiation.At the same time,the effect of the initial p H,photocatalyst dosage and co-exist substances were investigated and the results showed that BiU-9 could operate at a wide pH range（4-10）and displayed good resistance for co-existence of anions over SDZ removal.In addition,the capture experiments,electron spin resonance spectroscopy（ESR）,electrochemical test,photoluminescence spectrum and VB-XPS analysis proved that·O₂^-and h⁺were the main active substances in photocatalytic reactions,and the internal electric field in BiOI/UiO-66 p-n heterojunction effectively promoted the separation of photo-generated charge carriers.Finally,the degradation pathway and toxicity analysis of intermediate products indicated that SDZ has achieved effective detoxification during the photocatalytic reaction.This work provides a new approach for constructing p-n type heterojunctions between MOFs and bismuth-based semiconductors to improve the efficiency of photo-generated carrier separation.2.MIL-88A（Fe）and BOHP were synthesized by the solvothermal and hydrothermal methods,respectively.The MIL-88A（Fe）/BOHP heterojunction was fabricated by the high-energy ball milling method.The M3B7/Vis/H₂O₂ system exhibited excellent ENR degradation efficiency via photo-Fenton process,which was 23.125 and 102.778 times higher than those of MIL-88A（Fe）/Vis/H₂O₂ and BOHP/Vis/H₂O₂ systems.Furthermore,the study investigated the effect of H₂O₂ dosage,initial pH and coexisting substances on the degradation of ENR activity over M3B7/Vis/H₂O₂ system.Additionally,the results of XPS analysis and DFT calculation co-unraveled the formation of interfacial chemical bond（Fe-O-P bond）between MIL-88A（Fe）and BOHP,which could accelerate the electron transfer via reducing migration distance and the charge transfer energy barrier.Finally,the constructed M3B7/Vis/H₂O₂ system was a cost-optimal and green technology for antibiotic wastewater treatment based on Electrical Energy per Order（EE/O）concept,life cycle assessment（LCA）and quantitative structure–activity relationship（QSAR）analysis.This work provides a theoretical basis for building an interface chemical bond between MOF and bismuth-based semiconductors to accelerate electron transfer.