CO₂ as a Redox Shuttle Enables Photocatalytic Dehydrogenative Decarbonylation of Biomass-Derived Alcohols to Light...

The use of CO₂ as a redox shuttle offers an emerging strategy to regulate electron and hydrogen transfer in catalytic transformations, yet its potential remains largely unexplored. In particular, dehydrogenative decarbonylation of alcohols possesses a long-standing challenge, as it requires the controlled coupling of oxidative alcohol activation with reductive C─C bond cleavage, two intrinsically competing processes that are difficult to balance within a single catalytic system. Considering these, we demonstrate that CO₂ can resolve this mismatch by functioning as a dynamic redox shuttle in a heterogeneous photocatalytic platform. Under visible-light irradiation, the photocatalyst promotes sequential dehydrogenation of primary alcohols to aldehydes, followed by C─C bond scission and selective formation of alkanes. Mechanistic studies, including isotope labeling, radical trapping, atmosphere-dependent reactivity, and advanced quantum mechanical calculations reveal that CO₂ is not incorporated into the products but instead transiently interacts with reduced iron sites to facilitate catalyst turnover, suppress unproductive H₂ evolution, and direct hydrogen equivalents toward C─H bond formation. This redox-shuttling function enables the integration of oxidative and reductive steps within a single photocatalytic cycle, thus opening new opportunities for steering complex redox transformations in photocatalysis.