Enaminone-Linked Quasi-One-Dimensional Covalent Organic Frameworks for CO2 Photoreduction with Water

Quasi-one-dimensional covalent organic frameworks (Q1DCOFs) have emerged as promising platforms for photochemical energy conversion due to their low density of basal sites, abundant edge sites, and dual-chain-like structure. However, the development of Q1DCOFs in photocatalysis is still highly hindered by their limited linkage chemistry. Herein, we report a novel enaminone-linked Q1DCOF (En-Q1DCOF). The polar enaminone bonds together with dual-chain-like structure endow En-Q1DCOF with broad light adsorption and excellent excitonic dissociation abilities. Significantly, a record high CO yield of 3045 µmol g^{− 1} with approximately 100% selectivity was achieved in a 24 h reaction under gas-solid conditions without using any metal, photosensitizer, or sacrificial reagent. More interestingly, the hydrogen atom on nitrogen site in enaminone bond could assist in the activation of CO₂ molecule via hydrogen-bond interaction. This interaction leads to the strongest adsorption ability for CO₂ and the lowest energy barrier for the rate-determining step during CO₂ reduction over En-Q1DCOF compared to those over Mix-Q1DCOF and Im-Q1DCOF counterparts. All of these factors directly contribute to the superior activity of En-Q1DCOF in the photocatalytic CO₂ reduction to CO.