Site-defined Cu-O ensembles enable hydrogen-conserving light-driven ethane upgrading

Upgrading light alkanes to value-added olefins is a long-standing challenge, owing to the high stability of C–H bonds and the tendency for overoxidation at elevated temperatures. Here, we introduce a light-driven strategy for ethane dehydrogenation using Cu-doped TiO 2 , in which atomically dispersed Cu coordinated to bridging oxygen (O br–Cu ) creates well-defined [Cu–O] ensembles that orchestrate site-specific, stepwise C–H activation. Photogenerated holes localize at O br–Cu sites to initiate the first C–H cleavage, while adjacent Cu centers mediate β–H elimination and H 2 evolution. In contrast, minor β–H activation at O br–Ti sites generates *H species that cannot desorb due to a prohibitive coupling barrier with *H on O br–Cu , leading to Cu reduction and progressive deactivation. Co-feeding CO 2 restores the active Cu coordination environment and suppresses this deactivation process without perturbing the primary reaction pathway. This cooperative design achieves a C 2 H 4 production rate of 21.1 mmol g −1 h −1 with nearly stoichiometric H 2 evolution and an apparent quantum efficiency of 6.1% under 365 nm irradiation. These findings establish a site-defined, hydrogen-conserving route for photocatalytic alkane upgrading, offering a general blueprint for selective C–H bond transformations with long-term stability. Converting light alkanes into useful olefins is hard because strong bonds and heat drive overoxidation. This study uses a copper-doped titanium dioxide photocatalyst to steer bond breaking, yielding ethylene and hydrogen.