Synergy of Exciton and Carrier Pathways in a Single-Atom Photocatalyst for Photocatalytic Oxidation Coupling

Conventional photocatalytic systems are fundamentally constrained by the lack of concerted control over excitonic and charge-carrier dynamics, which limits quantum efficiency and scalability. To address this constraint, we present a poly(heptazine imide)-based photocatalyst bearing atomically dispersed iridium single-atom sites and electron-deficient terminal cyano groups, enabling the coupling of exciton- and carrier-mediated pathways. The iridium single-atom sites reduce the singlet–triplet energy gap to promote intersystem crossing and the generation of triplet excited states for enhanced energy transfer. In parallel, the terminal cyano groups form charge transport channels, which accelerate charge separation and interfacial electron transfer. The synergy between single-atom and cyano groups extends the light absorption range. This dual-pathway design enhances the formation of reactive oxygen species under visible light and enables visible-light-driven aerobic oxidative coupling reactions. Exciton-mediated energy transfer predominantly yields 1O2, whereas carrier-mediated electron transfer yields O2•–; together, these processes drive oxidative coupling. The system operates without sacrificial agents or additional cocatalysts, offers a broad substrate scope with gram-scale productivity, and exhibits five cycles of stability. This approach is compatible with the gram-scale preparation of single-atom catalysts, underscoring its potential for practical application.