Research On The Construction Of Bi-based Metal-organic Framework Photocatalyst With Heterojunction Structure And Their Degradation Of Organic Wastewater

The problem of environmental pollution caused by organic wastewater has become increasingly serious in China,and the degradation of antibiotics has become a pressing issue.While chemical,physical,and biological methods have been widely used for tertiary treatment,these methods often require high equipment and tool costs.In contrast,photocatalytic technology can directly use light energy,making it highly efficient and cost-effective.Semiconductors have been used as photocatalysts for a long time,but most single-phase semiconductors cannot complete the difficult task of narrowing the band gap while increasing the redox potential.To solve this problem,composite heterojunctions have been constructed.Metal-organic frameworks(MOFs)are semiconductor-like materials in which metal ions are coordinated with organic ligands to form a periodic network chemical framework.MOFs have high specific surface areas,diverse topologies,and unsaturated metal center sites,which make them ideal for coupling with metal oxides,g-C3N4,and Bi-based semiconductors.Bi is an emerging metal center ion in the field of MOFs photocatalysis due to its abundant resources,low manufacturing cost,and unique layered crystal structure.Therefore,CAU-17,which is easy to synthesize,was selected as the research material for this paper.The paper focuses on the design of heterojunction structures and material preparation around Bi-MOFs(CAU-17)to explore the possibility of CAU-17 application in photocatalysis through in-situ growth and pyrolysis derivation.The band adjustment tools CeO2,g-C3N4,and BiOBr were selected.Tetracycline was used as the target compound to verify the photoinduced degradation ability.The construction of heterojunctions was accompanied by the adjustment of its morphology.The specific research content is as follows:In the first chapter,CeO2 nanowires were obtained without the use of surfactants by controlling temperature and time.The SEM images show that CeO2 nanowires are buried inside CAU-17,forming a tight heterojunction interface between the two.The characterization results confirmed that CeO2 introduced oxygen vacancies and promoted the transfer of photogenerated carriers.Under visible light irradiation,CE-15 degraded 55.2%TC in 60 min,and the degradation rate reached 58.5%within 150 min.In the second chapter,CAU-17/g-C3N4(CG-X)composite photocatalytic materials were prepared by in situ growth method.The layered g-C3N4 provided CAU-17 with a growth plane,and the original rod-like fracture presented a blooming "lily".The special "petals" of the composite material were conducive to collecting visible light,and the tight Z-shaped heterojunction interface also retained the strong oxidation-reduction potential,which produced abundant superoxide radicals and hydroxyl radicals.Therefore,it had an excellent degradation effect on tetracycline wastewater.The removal rates of CG-8 were 2.3 times and 1.79 times higher than those of CAU-17 and g-C3N4,respectively.In the third chapter,BiOBr nanosheets were loaded onto the surface of CAU-17 using an impregnation method,and CAU-17-derived materials(Bi-Br-5)deposited by BiOBr nanosheets were prepared by high-temperature calcination.Pyrolysis resulted in more pores in MOFs,which effectively captured pollutant molecules.Bi-Br-X had a smaller band gap and internal resistance,degrading tetracycline faster(79.8%degradation within 60 minutes and 94%RhB degradation).The successful construction of a Z-heterojunction(Bi-Br-5)represents a significant step in the exploration of pyrolyzed CAU-17 materials.