The visible‐light‐driven photocatalytic CO2 reduction is one appealing approach to simultaneously mitigate the energy crisis and environmental issues. It is highly desirable but challenging to selectively and efficiently convert CO2 into desirable products. Herein, a covalent organic framework hosting metalloporphyrin‐based carbon dots (M‐PCD@TD‐COF, M = Ni, Co, and Fe) is first presented, which serves as heterogeneous catalysts for CO2 photoreduction. M‐PCD@TD‐COF not only enriches available COF‐based catalytic materials, but also provides suitable environment for CO2 adsorption and activation on metalloporphyrin‐based carbon dots. The advantages of the host environment in COFs are highlighted by the satisfactory catalytic activity and remarkable selectivity of CO2‐to‐CO conversion over H2 generation up to 98%. The photocatalytic system is effective for both pure CO2 and the simulated flue gas. This work provides new protocols for the rational design of COF‐based heterogeneous catalysts for selective CO2 photoreduction.

Covalent organic frameworks (COFs) are promising platforms for understanding photocatalytic CO 2 reduction processes owing to their predesignable structures and tailor-made functions. Herein, a nickelmodified COF composed of N-acylhydrazone-linked electron-donor and electron-acceptor dyads (H-COF-Ni) is reported. H-COF-Ni generates 5694 µmol g −1 of CO with 96% selectivity over H 2 evolution in 2 h under visible light irradiation, which greatly outperforms that of typical iminelinked counterpart. Experimental and theoretical results have demonstrated that metal active sites in host frameworks are deprived by 2,2′-bipyridine additive to form new catalytic active species, the separation and transfer process of the photogenerated charge carriers are not main reason for their activity difference. The linkage-dependent activation of CO 2 molecules on Ni centers is responsible for high photocatalytic efficiency. This study provides new protocols to improve CO 2 photoreduction performance through the modification of linkage microenvironments.