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

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.