Design,Synthesis And Photocatalytic Properties Of Triazine-Based Organic Framework Materials

Solar energy is a green and clean renewable energy,and how to utilize this clean energy effectively has been widely investigated.Photocatalysis is an efficient approach to convert solar energy into chemical energy which has advantages of mild reaction conditions,environment-friendly,low-energy,etc.Photocatalysis has been demonstrated can function well in degradation of organic dyes and selective synthesis of organic monomers.The present common photocatalysts usually encounter the disadvantages of poor stability,low solar energy utilization efficiency,environmentally unfriendliness and reliance on noble metal,etc.Hence,the exploration of the metal-free photocatalytic materials with extensive visible light response,excellent stability and recycling performance is a focus of current research.Triazine ring is an emblematic electron-withdrawing and nitrogen-rich structure.A rational design of grafting organic units on triazine ring could change the electronic band structure,improve the quantum efficiency and enhance the region of photoabsorption.It has been reported that 3D rigid and kinked building blocks are beneficial to construct highly porous polymers and N,N’-bicarbazole exhibits a nearly vertical structural unit.Herein,taking the merits of both triazine ring and N,N’-bicarbazole into consideration,we designed and synthesized triazine-based organic framework materials with N,N’-bicarbazole structural unit,and the photocatalytic performance of some triazine-based organic frameworks was explored.The primary research contents are showing as follows:Part one:Two novel N,N’-bicarbazole-based covalent triazine organic frameworks（BC-CTF and Ph-BC-CTF）were readily prepared by mild trifluoromethanesulfonic acid-catalyzed synthesis.The N,N’-bicarbazole-based CTFs has the advantages of excellent stability（580℃,N₂）,high surface areas(BC-CTF:934 m² g^-1,Ph-BC-CTF:967 m² g^-1),excellent CO₂ adsorption capacity(BC-CTF:140.1 mg g^-1,Ph-BC-CTF:131.7 mg g^-1,273 K)and strong absorption in the visible range（250 nm-600 nm）.The two CTFs have comparable surface areas with the ionothermal frameworks but avoid partial carbonization and energy loss caused by high temperature.The EPR signals exhibited electron-hole pairs were generated in N,N’-bicarbazole-based CTFs upon visible light irradiation.Therefore,the CTFs were applied to photocatalysis for the degradation of rhodamine B and selective oxidation of thioanisoles to sulfoxides.It demonstrated that the N,N’-bicarbazole-based CTFs exhibited excellent photocatalytic performance,substrate universality and cyclic stable performance.Part two:Combining the hydrogen bonding motif 2,4-diaminotriazinyl group with the N,N’-bicarbazole skeleton,two hydrogen-bonded organic frameworks（BC-HOF and Ph-BC-HOF）was obtained via self-assembly method.The structures and composition of the two HOFs were studied detailedly.It was indicated N,N’-bicarbazole-based HOFs have excellent thermal stability and nitrogen rich structure,and may exhibit promising application in carbon dioxide storage and photocatalysis.