Quasi-one-dimensional enaminone-linked covalent organic frameworks for efficient CO₂ photoreduction

Quasi-one-dimensional covalent organic frameworks 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 quasi-one-dimensional covalent organic frameworks in photocatalysis is still highly hindered by their limited linkage chemistry. Herein, we report an enaminone-linked quasi-one-dimensional covalent organic framework. The polar enaminone bonds together with dual-chain-like structure endow enaminone-linked quasi-one-dimensional covalent organic framework with broad light adsorption and effective excitonic dissociation abilities. Significantly, a high CO yield of 3045 μmol g-1 with approximately 100% selectivity was achieved in a 24 h reaction under gas-solid conditions. 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 enaminone-linked quasi-one-dimensional covalent organic framework compared to those over mixture-linked quasi-one-dimensional covalent organic framework and imine-linked quasi-one-dimensional covalent organic framework counterparts. All of these factors directly contribute to the enhanced activity of enaminone-linked quasi-one-dimensional covalent organic framework in the photocatalytic CO2 reduction to CO. This study reports a new kind of En-Q1DCOF. The polar enaminone bonds and dual-chain-like structure endow En-Q1DCOF excellent photoelectric conversion performance. Furthermore, the N-site H atom in enaminone facilitates CO₂ activation via H-bonding.