Synthesis Of Zirconium-Based Organic Polyhedral Materials And Investigation Of Their Photocatalytic Properties

As we all know,metal-organic frameworks（MOFs）have been used successfully in various applications.Metal-organic polyhedra（MOPs）as a brother of MOFs in the field of metal-organic materials,were discrete molecular entities with high symmetry and self-assembled by organic linkers and metal nodes.Distinguished from MOFs,MOPs are not infinite network structures,but closed caged structures.They have also been regarded as potential candidates for gas adsorption/separation,nanocatalysis,chemical sensors and as secondary building blocks for synthetic MOFs,which have attracted widespread attention in various fields.Antibiotics are widely used in the medical and animal husbandry industry,as these industries develop,the pollution of water caused by them is gradually severe.One of these antibiotics,tetracycline,is a broad-spectrum antibiotic and is one of the main antibiotics used in veterinary medicine,human treatment and as a feed additive in the agricultural sector.Due to its lower cost and higher antibacterial activity,it is widely used as a veterinary drug for the prevention and treatment of animal farms to cure a wide range of infectious diseases.Also,quinolone antibiotics（QNs）are a type of broad-spectrum antibiotic that have been detected in aquatic environments around the world.Among many treatment methods,photocatalysis is considered to be one of the practical and effective methods,and it is a green method that does not cause secondary pollution.Zr-based metal-organic polyhedra（Zr-MOPs）have focused the spotlight on photocatalytic applications,mainly owing to their excellent properties in tunable semiconducting characteristics and outstanding water stability.Based on this,we selected Zr-MOPs materials and their composites synthesized by different methods for the photocatalytic degradation of antibiotics in water,characterized the materials and properties to investigate their photocatalytic performance,and proposed reasonable and feasible photocatalytic degradation principles based on this.（1）An amino-functionalized Zr-based organic polyhedron（denoted ZrT-1-NH₂）,synthesised under the solvothermal method,has been selected as the photocatalyst for the removal of tetracycline（TC）.The effects of adding dosages,pH values of TC degradation efficiency were investigated,and the results showed that the photocatalytic degradation of TC（50 mg/L）was 62%within 90 min at a catalyst dosage of 20 mg and pH=6.The material was better effective in photocatalysis degradation of tetracycline antibiotic.In addition,the trapping experiments reveal that hydroxyl radical（·OH）and superoxide radical（·O₂^-）,serving as active species,play major roles in the photocatalytic process.In addition,a reasonable mechanism for（2）the photocatalytic process is put forward.（3）Amino-functionalized Zr-based organic polyhedra were synthesized by microwave-assisted synthesis method（MW-ZrT-1-NH₂）,after which Ag Cl nanoparticles were incorporated into ZrT-1-NH₂ by a facile in-situ growth method,leading to the formation of Ag Cl/ZrT-1-NH₂ composites.Photocatalytic activity under visible light was assessed via degrading broad-spectrum antibiotics（including tetracyclines and quinolones）.The effect of important parameters,including pH value,catalyst dosage,initial antibiotic concentration and the weight ratio of Ag Cl to ZrT-1-NH₂,were investigated.The results showed that the Ag Cl/ZrT-1-NH₂ composites with a weight ratio of 30%degraded CTC（50 mg/L）,OTC（50mg/L）,NOF（10 mg/L）and TC（50 mg/L）with the efficiency of 79.45%,72.65%,73.27%and83.99%,respectively,within 90 min（20 mg,pH=6）.Based on the characterization results such as X-ray photoelectron spectroscopy（XPS）spectra,the transient photocurrent response,electrochemical impedance spectroscopy and electron spin resonance（ESR）spectra,it is proposed that Z-scheme heterojunction and surface plasmon resonance（SPR）effect（caused by a small quantity of Ag nanoparticles）significantly promote the separation of photoelectron and hole.This work presents that zirconium-based metal-organic polyhedra（Zr-MOPs）may be promising photocatalysts for the removal.And this research will introduce new ideas for the synthesis of Zr-MOP based composites,and exhibit a promising strategy to establish MOP-based heterojunction for environmental remediation.