Study On The Adsorption And Photocatalytic Degradation Performance Of Tetracycline By Metal-Organic Framework-Based Materials

Tetracycline（TC）is one of the most widely used antibiotics.Its residues in the environment have caused great harm to the ecological environment and human health.Adsorption and photocatalysis are potential and efficient methods to remove tetracycline.Adsorption technology can enrich tetracycline through physical or chemical adsorption of adsorbents,while photocatalysis technology can degrade tetracycline into non-toxic and harmless by-products,such as CO₂ and H₂O,through electrons and holes generated by photoexcitation of photocatalyst.However,the current adsorbents have some problems such as low tetracycline adsorption efficiency,difficult recovery and high cost.Existing photocatalysts have problems such as low photodegradation efficiency and weak response to visible light.Therefore,the development of materials with high efficiency adsorption or photocatalysis has great research significance and application prospect.Metal-organic frameworks（MOFs）are a new type of highly ordered porous crystal materials that can be self-assembled from multifunctional organic ligands and metal centers.Metal-organic framework（MOFs）derived materials continue the characteristics of the original MOFs,such as large specific surface area and high porosity,but also can form more pore structures and have excellent chemical stability.In view of this,this study prepared MOFs composite and MOFs derived material,and explored their photocatalytic and adsorption properties for tetracycline,respectively.（1）Magnetic nitrogen-doped carbons encapsulated cobalt nanoparticles（Co@NC）were prepared by solvothermal synthesis of Co-HMT as precursor in nitrogen atmosphere and used for tetracycline adsorption and removal.The results show that the best samples synthesized at700℃（Co@NC-700）have mesoporous structure,abundant oxygen-containing functional groups,rich doped nitrogen content and ultrahigh cobalt content（86.1 wt%）.Based on the above structural characteristics,Co@NC-700 showed a very large adsorption capacity of 3058mg.g^-1 TC and good reusability（removal efficiency maintained 94.22%after four cycles）.The experiment further shows that cation exchange,π-πelectron donor-acceptor（EDA）interaction,cation-πbonding,hydrogen bonding and surface complexation play a leading role in the adsorption of TC.Density functional theory calculations show that pyridine-N enhance theπ-πEDA interaction,and the encapsulated cobalt forms complex bond with TC,thus enhancing the adsorption efficiency.（2）A series ofγ-Fe₂O₃-ZIF8 composites were prepared by in-situ loadingγ-Fe₂O₃-ZIF8on regular rhombic dodecahedron for photocatalytic degradation of tetracycline under visible light.The best sample 30γ-Fe₂O₃-ZIF8 showed microporous structure and large specific surface area(1187.44 m²·g^-1).The band gap ofγ-Fe₂O₃-ZIF8 is narrower than that of pure ZIF8,indicating that 30γ-Fe₂O₃-ZIF8 is more easily excited by visible light.Photocurrent test and fluorescence test indicate that 30γ-Fe₂O₃-ZIF8 has higher photogenerated electron-hole separation efficiency than a single material.The photodegradation results showed that 30γ-Fe₂O₃-ZIF8 exhibited better visible light catalytic activity,and the photodegradation efficiency reached 86.9%within 3 h,which was superior to that of commercial Ti O₂,ZIF8 andγ-Fe₂O₃.30γ-Fe₂O₃-ZIF8 also has good cycle stability,and the degradation efficiency remains stable at 87%after four cycles.30γ-Fe₂O₃-ZIF8 excellent photocatalytic degradation performance of tetracycline,attributed to the formation of"n-n"type heterojunctionγ-Fe₂O₃and ZIF8,in improving the separation efficiency of electron hole pairs,but also improve the photoresponse ability,so as to further improve the photocatalytic activity.