1D Covalent Organic Frameworks with Tunable Dual-Cobalt Synergistic Sites for Efficient CO2 Photoreduction.

Abstract

Diatomic catalysts enhance photocatalytic CO₂ reduction through synergistic effects. However, precisely regulating the distance between two catalytic centers to achieve synergistic catalysis poses significant challenges. In this study, a series of one-dimensional (1D) covalent organic frameworks (COFs) are designed with adjustable micropores to facilitate efficient CO₂ photoreduction. CO₂ molecules are anchored between dual-cobalt centers within micropores, thus effectively reducing their activation energy and initiating the photocatalytic process. Additionally, the formation of *COOH intermediates is significantly influenced by the coordination microenvironment around dual-cobalt sites. Notably, COF-Co-N₄ exhibited remarkable CO₂ photoreduction activity with a CO evolution rate of 110.3 µmol·g^-1·h^-1, which surpasses most of previously reported single-atom-site photocatalysts. Comprehensive characterization and density functional theory (DFT) calculations revealed that 1D COFs with dual-cobalt sites possess the ability to anchor CO₂ molecules, thereby enhancing the efficacy of synergistic catalysis. Simultaneously, COF-Co-N₄ with quadruple nitrogen coordination significantly reduced the energy barrier of crucial *COOH intermediate, facilitating efficient photocatalytic CO₂ reduction. This study meticulously modulated the coordination microenvironment surrounding dual-cobalt synergistic sites, providing new insight into the design of high-performance photocatalysts.