Paired Photoproduction of H₂O₂ and 3,4-Dihydroisoquinoline Over Covalent Pyrene-(Thio)urea Frameworks with Electron Push-Pull Effect

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 H₂O₂ yield rate of ~19 mmol g⁻¹ h⁻¹ under visible light and finally solid H₂O₂ products (Na₂CO₃ ⋅ 1.5H₂O₂) was collected after long-time irradiation. Under natural sunlight conditions, the H₂O₂ 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 O₂ adsorption and *HOOH desorption over thiourea units. This work provides a paired photosynthesis strategy of H₂O₂ and DHIQ over high-efficiency pyrene-(thio)urea COF photocatalysts with electron push-pull effect.