<p>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 Ni<sup>2+</sup>-reductive and Ti<sup>4-x</sup>-oxidative dual-active sites, achieving the regulation of generation, stabilization, and coupling of transient-stabilized radical pairs for formamide synthesis. NO<sub>2</sub><sup>−</sup> and CH<sub>3</sub>OH reactants are photo-activated on the Ni<sup>2+</sup>-Ti<sup>4-x</sup> dual-active sites to generate <sup>●</sup>NO and CH<sub>3</sub><sup>●</sup>O radicals, respectively. The <sup>●</sup>NO on Ni<sup>2+</sup> sites is stabilized through π backbonding formation resulting from the hybridization of 3 <i>d</i> (Ni<sup>2+</sup>) and π* (<sup>●</sup>NO) orbitals. The weak steric effect endows fast migration of transient CH<sub>3</sub><sup>●</sup>O to the neighboring Ni<sup>2+</sup>-<sup>●</sup>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 g<sub>cat</sub><sup>−1</sup> h<sup>−1</sup>. 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.</p>

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

  • Shujie Shen,
  • Jieyuan Li,
  • Xin Li,
  • Jielin Wang,
  • Chunling Zhang,
  • Fan Dong

摘要

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 CH3O 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 CH3O 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.