Promoting energy transfer pathway in porphyrin-based sp2 carbon-conjugated covalent organic frameworks for selective photocatalytic oxidation of sulfide

The sp² carbon-conjugated covalent organic frameworks (COFs) with fully π-conjugated lattice and high chemical stability are promising heterogeneous photocatalysts. Herein, we report the design and synthesis of a novel palladium (Pd) porphyrin-based sp² carbon-conjugated COF (PdPor-sp²c-COF) with an eclipsed AA stacking 2D structure. Interestingly, PdPor-sp²c-COF showed high crystallinity, good chemical stability, and a broad absorption of visible light. Moreover, compared to our previously reported metal-free Por-sp²c-COF, PdPor-sp²c-COF displays an improved photocatalytic performance in the selective aerobic oxidation of sulfides under green light irradiation. The systematic mechanistic studies testified that the enhanced photocatalytic activity can be ascribed to promoting energy transfer pathway over PdPor-sp²c-COF. Our study clearly demonstrates that it is favorable to promote the energy transfer pathway in sp² carbon-conjugated COFs by using metalloporphyrin-based molecular building blocks. This work will inspire us to design and synthesize novel photocatalysts based on COFs for the selective aerobic oxidation.