Harnessing CO₂ in organic synthesis via photo- and electrocatalysis

Carbon dioxide, an abundant, non-toxic, and renewable C1 source, has attracted significant attention as a sustainable feedstock in organic synthesis, offering dual benefits of CO₂ utilisation and greenhouse gas minimisation. Despite the thermodynamic stability and kinetic inertness of CO₂, which have long posed challenges for conventional transition-metal-based approaches, the field has undergone a paradigm shift. The open-shell catalysis driven by single-electron transfer (SET) processes has emerged as an alternative. In this review, we provide a comprehensive overview of recent mechanistic advances in photo- and electrochemically driven CO₂ valorisation, organised around four key synthetic domains: (i) regioselective carboxylation of olefins, arenes and alkynes; (ii) radical-mediated lactonisation; (iii) homolytic C(sp³)-H/X functionalisation via hydrogen/halogen atom transfer (HAT)/(XAT); and (iv) oxidative alkene cleavage strategies. We further examine the complementary nature of photoredox and electrochemical strategies through the lens of intermediate generation, catalyst design, and reaction engineering.