| The massive discharge of industrial dye wastewater and the abuse of antibiotics in the pharmaceutical industry have caused serious harm to water environment and human health.The photocatalytic technology has attracted more and more people's attention because of its simple operation,fast reaction,green and efficient performance.As we know,TiO2 is one of the most common photocatalytic materials for the degradation of organic pollutants,but it can only absorb ultraviolet light,which greatly limits its application under sunlight.Therefore,we need to develop more efficient photocatalytic materials driven by visible light.UiO-66-NH2 has been favored by many researchers due to its high specific surface area,super high stability,designability and photocatalytic activity.However,for UiO-66-NH2,photo-generated electrons and holes are easily recombined,and the visible light absorption efficiency is low,which limits its application in photocatalytic.Therefore,this paper uses the construction of heterojunction and the loading of metal nanoparticles to improve the photocatalytic degradation activity of UiO-66-NH2 based materials on dyes and antibiotics.At the same time,the degradation mechanism and reaction path of the photocatalytic system are further discussed.(1)The Ag3PO4/UiO-66-NH2 Z-scheme heterojunction composite material was prepared by a simple co-precipitation method.Under visible light irradiation,the degradation of methylene blue(MB)and norfloxacin(NOR)was significantly improved by the composites compared with Ag3PO4 and UiO-66-NH2.The construction of the Z-scheme heterojunction significantly improved the utilization of visible light,and the increase of the composite surface area provides more photocatalytic active sites.At the same time,the trapping agent experiment showed that·OH,·O2-and h+were all involved in photocatalytic degradation.The results of the photocatalytic mechanism study showed that the Z-scheme photocatalytic reaction mechanism can explain the degradation process of MB,indicating that MOFs-based composite materials can be used as effective photocatalysts for the degradation of pollutants.(2)The Bi2WO6/UiO-66-NH2 heterojunction material was prepared by a two-step solvothermal method.The structure and composition of the sample were characterized by XRD,FT-IR,XPS and other means.The morphology of the composite material was characterized by scanning and transmission electron microscope.The photoelectrochemical performance of the composite material was analyzed by transient photocurrent response,EIS and PL spectroscopy.The construction of heterojunction accelerates the separation of photogenerated carriers and achieves the purpose of improving photocatalytic activity.When the feed ratio was n Zr:n Bi=1:2,Bi2WO6/UiO-66-NH2 had the best catalytic activity for rhodamine B(Rh B)and tetracycline(TC).The results of cyclic experiments verified that the composite material had good stability.The degradation mechanism of the system was speculated by free radical trapping experiment.(3)The 3D flower-sphere UiO-66-NH2/Bi/BiOBr Z-scheme heterojunction composite material was successfully prepared for the first time through in-situ reduction and self-assembly process using ethylene glycol as solvent and reducing agent.This study shows that:The 3D flower-sphere structure is beneficial to improve the light absorption of the photocatalyst,shorten the light diffusion path,and increase the active site of the catalyst.The introduction of UiO-66-NH2 greatly increases the specific surface area of the composite material,so as to provide more adsorption and catalytically active sites for the photocatalytic process.The construction of the indirect Z-scheme heterojunction with metal Bi as the electron conduction bridge between UiO-66-NH2 and BiOBr effectively improves the separation efficiency of photogenerated carriers.This makes UiO-66-NH2/Bi/BiOBr heterojunction materials have good photocatalytic performance for tetracycline(30 mg/L TC)and norfloxacin(10 mg/L NOR)under visible light irradiation.Cycling experiments and XRD and XPS characterization results before and after the photocatalytic reaction verify that the composite have good reusability and stability.In addition,the possible degradation mechanism is inferred through capture agent experiment and ESR spectrum analysis. |
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