Synthesis And Oxygen Reduction Properties Of Thiophene Rich Fully Conjugated Three-dimensional Covalent Organic Frameworks

Covalent Organic Frameworks（COFs）,as a new class of material which is widly used in semiconductor,energy storage,photoelectric materials and other fields.Among them,fully conjugated COFS have greater advantages in optical,electrical,magnetic and other applications.However,at present,fully conjugated COFs are mostly two-dimensional COFs,and there are few examples of three-dimensional COFs.The reason is that the lack of three-dimensional fullyπconjugated connectors limits the design and synthesis of fully conjugated three-dimensional COFs.Theoretically,compared with similar two-dimensional COF,fully conjugated three-dimensional COF has the advantages of network structure,larger specific surface area and more open sites,so its performance will be better.Therefore,this paper designs a new three-dimensional conjugate connector,and further synthesizes a fully conjugate three-dimensional COF.1、In this paper,A saddle like thiophene linked ligand COTh Th-CHO was designed and synthesized.The ligand is a three-dimensionalπconjugate construction unit,which can be used for the synthesis of fully conjugated three-dimensional COF.In addition,we further synthesized a fully conjugated three-dimensional covalent organic framework material BUCT-COF-11 by Schiff base polycondensation of ligand COTh Th-CHO and p-phenylenediamine（DAB）by solvothermal method.A series of characterization and analysis show that BUCT-COF-11 has high crystallinity and high thermal stability.The successful synthesis of BUCT-COF-11 broadened the idea of researchers to design fully conjugated three-dimensional covalent organic framework materials.2、The electrochemical oxygen reduction reaction（ORR）performance of BUCT-COF-11 was also tested,and its half wave potential reached 0.72 V.Then BUCT-COF-11 is used as cathode material to form zinc air battery.The power density of the battery reaches 0.172 W cm^-2at 0.42 V.This is the first time to apply fully conjugated three-dimensional COF material to zinc air battery.The zinc air battery works for 60 h at 5 m A cm^-2current density,and the battery voltage attenuation is only 1.3%,which proves that BUCT-COF-11 has excellent stability.The synthesis of BUCT-COF-11 promotes the development of fully conjugated three-dimensional covalent organic framework materials in the field of electrocatalysis and the development of metal free ORR catalysts.