Single‐Atom Metal Sites Anchored Hydrogen‐Bonded Organic Frameworks for Superior “Two‐In‐One” Photocatalytic Reaction

Abstract Photoredox catalysis is a green solution for organics transformation and CO₂ conversion into valuable fuels, meeting the challenges of sustainable energy and environmental concerns. However, the regulation of single‐atomic active sites in organic framework not only influences the photoredox performance, but also limits the understanding of the relationship for photocatalytic selective organic conversion with CO₂ valorization into one reaction system. As a prototype, different single‐atomic metal (M) sites (M²⁺ = Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺) in hydrogen‐bonded organic frameworks (M‐HOF) backbone with bridging structure of metal‐nitrogen are constructed by a typical “two‐in‐one” strategy for superior photocatalytic CN coupling reactions integrated with CO₂ valorization. Remarkably, Zn‐HOF achieves 100% conversion of benzylamine oxidative coupling reactions, 91% selectivity of N‐benzylidenebenzylamine and CO₂ conversion in one photoredox cycle. From X‐ray absorption fine structure analysis and density functional theory calculations, the superior photocatalytic performance is attributed to synergic effect of atomically dispersed metal sites and HOF host, decreasing the reaction energy barriers, enhancing CO₂ adsorption and forming benzylcarbamic acid intermediate to promote the redox recycle. This work not only affords the rational design strategy of single‐atom active sites in functional HOF, but also facilitates the fundamental insights upon the mechanism of versatile photoredox coupling reaction systems.