Kinetics-controlled radical coupling on dual redox-active sites for selective formamide production

Catalytic construction of C-N bonds remains a pivotal challenge due to unmatched radical-radical coupling kinetics. Here, we design a redox-enhanced photosynthesis system with separated Ni2+-reductive and Ti4-x-oxidative dual-active sites, achieving the regulation of generation, stabilization, and coupling of transient-stabilized radical pairs for formamide synthesis. NO2− and CH3OH reactants are photo-activated on the Ni2+-Ti4-x dual-active sites to generate ●NO and CH3●O radicals, respectively. The ●NO on Ni2+ sites is stabilized through π backbonding formation resulting from the hybridization of 3 d (Ni2+) and π* (●NO) orbitals. The weak steric effect endows fast migration of transient CH3●O to the neighboring Ni2+-●NO interface, facilitating the generation of *OC-NO intermediate, subsequently producing formamide alongside proton transfer pathways, achieving a selectivity of 99.5% and production rate of 1.66 mol gcat−1 h−1. This work demonstrates principles for orbital-mediated radical stabilization and kinetics-regulated radical-radical coupling, providing a paradigm for overcoming kinetic limitations for diverse radical-mediated catalytic reactions. Researchers developed a dual-active-site photocatalyst that stabilizes ●NO radicals on Ni2+ sites while coupling them with transient CH3●O radicals, achieving 99.5% selectivity and g-scale formamide production by kinetics-controlled radical coupling.