Synthesis Of COF Derived Materials And Application In The Degradation Of Levofloxacin By Activated PMS

As one of the emerging organic pollutants,the harm of antibiotic pollution in the water environment to humans and ecosystems has attracted great attention,and how to effectively remove antibiotics in wastewater is the key to solving the pollution problem.In recent years,Advanced oxidation technology based on persulfate(PMS)has attracted the attention of many researchers due to its strong oxidation,long half-life and wide pH range.In the selection of persulfate activators,carbon material is an efficient and green catalyst.However,due to the complex and difficult modification process,the activity improvement space is small and its further application is limited.Covalent organic frameworks(COFs)composed of non-metallic elements,such as C,N,O,and H,are ideal precursors due to their large specific surface area,regular pore structure,and easy functionalization.In this paper,a COF rich in triazine and C=O structure was used as the precursor to prepare composite materials,non-metal doping and porous carbon materials,while giving full play to the characteristics of COF,also obtained further structural optimization.COFs derived materials show excellent catalytic PMS activation activity,and the corresponding activation mechanism is studied,which provides new ideas and methods for the exploration of new carbon-based materials.The specific research work and results are as follows:(1)Ultrasmall cobalt nanoparticles supported COF-derived materials(Co-C500COF)were prepared by simple hydrothermal and calcination.The Co-Nx sites were formed and the edge C=O active sites were released.Co-C500COF can activate PMS in a wide pH range and maintain more than 90%levofloxacin degradation efficiency.Co-Nx and C=O act as dual active sites to rapidly activate PMS to produce singlet oxygen(1O2)to efficiently remove pollutants.In addition,the toxicity of levofloxacin degradation intermediates to environmental organisms is effectively alleviated.Co-C500COF is an efficient,stable and environmentally friendly promising catalyst.(2)COF was directly pyrolyzed at high temperature to obtain nitrogen and oxygen codoped carbon materials(NOC).At high temperature,the material forms carbon lattice defects through the lack of N atoms and the rearrangement of carbon atoms at about 900℃,which is the key to the improvement of catalytic activity.NOC-900 degraded levofloxacin 100%within 90 min,and the degradation rate increased by 2.5 times.The generation of lattice defects increases the adsorption and activation of PMS,shortens the migration distance of active species and accelerates the degradation of pollutants.This study proves that COFs is an ideal carbon material precursor and provides a new idea for defect engineering.(3)On the basis of the previous part of the work,ammonium chloride was used as an activator,mixed with COF precursor and pyrolyzed at 800℃.Ammonium chloride was decomposed at high temperature to produce NH3 and HCl to obtain mesoporous carbon material(Nv-NC),which promoted the transfer of molecules on the surface of the material.The alkaline atmosphere promoted the oxygen functionalization of the defect edge,and produced a large amount of C=O as active sites to greatly improve the PMS activation performance of the catalyst.The activated Nv-NC-2 can remove levofloxacin 100%within 40 min by activating PMS,and the activity is increased by about 7 times.Nv-NC-2 still maintains high catalytic activity in a wide pH range or under the influence of environmental anions.This study improves the catalytic activity of carbon materials by simple activation technology,which provides a new idea for the surface modification of carbon materials.