Elemental Doping Boosts Charge-Transfer Excitonic States in Polymeric Photocatalysts for Selective Oxidation Reaction.

Energy-transfer-mediated synthetic reactions play vital roles in the production of high-value-added organics, where the long-lived exciton harvesting is an essential precondition for the process. However, for semiconductors with strong excitonic effects like conjugated polymers, their predominant Frenkel exciton with a short lifetime in the unified framework gives rise to low efficiency photocatalysis. Herein, we propose the boosting of the charge-transfer exciton with a long-lived state by introducing spatially separated electron and hole regions. By taking polymeric carbon nitride (PCN) as a prototype, we demonstrate that sulfur doping leads to the formation of electron donor and acceptor motifs in the tri-s-triazine-based backbone, which would accommodate long-lived excitonic states with remarkable charge-transfer characteristics. The extraordinary long-lived charge-transfer exciton harvesting endows sulfur-doped PCN with high-efficiency photocatalytic performance in O generation and selective oxidation of organic sulfides. This work provides a brand new perspective for designing advanced photocatalysts for energy-transfer-mediated sunlight utilization.