Atomically dispersed iron on carbon nitride with enhanced oxygen adsorption for efficient and scalable photooxidation

Selective oxidation of C-H bonds represents a pivotal transformation for upgrading hydrocarbon feedstocks into value-added chemicals, yet achieving this under mild conditions remains a formidable challenge. We herein disclose a single-atom photocatalytic system featuring nonsymmetric Fe-N₃Br sites anchored on melem that enables efficient photooxidation of C(sp³)-H bonds under mild conditions. The coordination environment facilitates Griffiths-type O₂ adsorption and realizes a high toluene conversion rate of 9.27 × 10⁴ μmol g^-1 h^-1. Experimental and theoretical studies indicate that the Fe-N₃Br configuration reduces the Fe 3d splitting energy, enhances the O₂ adsorption, and facilitates O₂ activation, thereby promoting superoxide radical (•O₂^-) generation. The catalyst demonstrates broad functional group tolerance (43 examples, up to 97% yield), and good scalability, enabling a 1000 mmol-scale continuous-flow reaction. This work demonstrates the importance of the single-atom site coordination in governing oxygen activation and provides a scalable, green photocatalytic platform for C-H functionalization.