Paired Photoproduction of H<sub>2</sub>O<sub>2</sub> and 3,4‐Dihydroisoquinoline Over Covalent Pyrene‐(Thio)urea Frameworks with Electron Push‐Pull Effect
Tao Yang, Fantao Kong, Yue Chen, Aiguo Kong, Xiangzhi Cui, Jianlin Shi
Abstract
Abstract Pairing photocatalytic 1,2,3,4‐tetrahydroisoquinoline semi‐dehydrogenation reaction (THIQ‐SDR) with two‐electron oxygen reduction reaction (2e − ORR) is a green solar to chemical strategy by simultaneously utilizing the photo‐excited electrons and holes. However, it is still short of high‐efficiency photocatalyst to drive two reactions above. In the present work, crystalline pyrene‐thiourea/urea covalent organic frameworks (COF−Py−S and −O) were synthesized and demonstrated as high‐performance metal‐free photocatalysts. In particular, COF−Py−S exhibited higher 2e − ORR to H 2 O 2 yield rate of ~19 mmol g −1 h −1 under visible light and finally solid H 2 O 2 products (Na 2 CO 3 ⋅ 1.5H 2 O 2 ) was collected after long‐time irradiation. Under natural sunlight conditions, the H 2 O 2 production rate over COF−Py−S further increased to ~51 mmol g −1 h −1 , among the best COF photocatalysts. COF−Py−S also showed high THIQ‐SDR conversion (~100 %) with 3,4‐dihydroisoquinoline (DHIQ) selectivity of ~92 %. Theoretical calculations reveal stronger electron push‐pull effect of COF−Py−S than COF−Py−O, enhancing its photoinduced charge carries, and a four‐step 2e − ORR mechanism with thiourea as the active sites has been confirmed as well as the mechanism of THIQ‐SDR to DHIQ, featuring lower energy barriers for O 2 adsorption and *HOOH desorption over thiourea units. This work provides a paired photosynthesis strategy of H 2 O 2 and DHIQ over high‐efficiency pyrene‐(thio)urea COF photocatalysts with electron push‐pull effect.