Covalent Organic Framework:Synthesis And Photocatalytic Applications

In the process of rapid economic development,there is a huge dependence on energy and environment,which brings environmental pollution,resource depletion and other problems that have become a major obstacle to the sustainable development of human beings.Therefore,the development and utilization of new,clean,renewable energy has become the focus of scientific research in recent years.As a kind of inexhaustible renewable and clean energy,solar energy has important applications prospect in photoelectricity,photoheat and especially in photochemical conversion.How to realize the effective use of light energy through the accurate design of materials has become a hot topic in the field of chemical materials at home and abroad.Among other materials,covalent organic frameworks(COFs)materials stand out because of their largeπ-conjugated structure and their ability to be chemically modified to regulate their energy band,thus extending the range of light absorption and enhancing the ability of light collection and charge transfer.In this thesis,we aim to design and synthesize photocatalytic active COFs with clear structure,and promote photoexciton generation,migration and charge separation through precise regulation of donor-receptor(D-A)structure,so as to further improve the photocatalytic performance.The details are as follows:(1)By adjusting the arrangement structure of strong electron-absorbing benzothiadiazole unit and electron-donating benzene ring unit in COFs,two kinds of isomerized COFs(BT-COF1 and BT-COF2)were designed and synthesized.Compared with BT-COF1,BT-COF2 has narrower band gap,smaller electrochemical impedance and more obvious charge transfer performance.Therefore,BT-COF2 has superior catalytic performance in the photocatalytic oxidation of sulfide,and can achieve high performance catalysis under natural light.(2)By adjusting the ratio of the number of electron-giving units and electron-absorbing units in the frame,the influence on photocatalytic performance was explored and the structure-activity relationship was deeply understood.The specific implementation is to select the phenyl unit as the electron donor and prepare COFs materials by combining with different amounts of strong electron absorbing benzothiadiazole unit monomer.Based on the excellent photochemical and photophysical properties of COFs,we investigated the influence of donor-acceptor number relationship in D-A configuration on the catalytic performance of COFs by comparing their catalytic performances in photocatalytic oxidation.By adjusting the arrangement and quantity ratio of donors and acceptors in the molecular level structural units in the covalent organic framework materials,we realize the precise regulation of the D-A configuration.Through a series of characterizations and photocatalytic applications of this series of COFs,the influence of the isomerism and quantity relationship of D-A configuration on the photocatalytic performance of COFs was explored.We aim to provide a new idea and method for the design and preparation of D-A COFs materials with photocatalytic activity through the content of this thesis.It will broaden the way for photocatalytic application of COFs materials.