Structurally engineered hydroxylated covalent organic framework for CO₂ photoreduction via dual-metal sites and spatially directed photosensitizer

Metal-coordinated covalent organic frameworks have attracted extensive attention in the field of CO2 photoreduction to CO due to their high electron affinity and tunable structure. However, achieving efficient CO2 activation requires overcoming the challenges of multi-electron transfer and intermediate stabilization, necessitating multifactorial optimization such as metal site cooperation, photosensitizer anchoring, and spatial alignment. Herein, we designed and fabricated a hydroxyl-functionalized COF featuring dinuclear Co/Zn sites and incorporated [Ru(phen)3](PF6)2 as the photosensitizer for photocatalytic reduction of CO2 to CO. When the ratio of Co(II) and Zn(II) in the dinuclear COF was 1:2, the obtained isostructural COF-Co1Zn2 showed enhanced CO production, with the CO conversion rate reached 46062 μmol gCo−1 h−1, which was three times higher than the CO production of the single metal COF (COF-Co: 15309 μmol gCo−1 h−1). DFT calculation and photoelectrochemical results supported the enhanced photocatalytic CO2 reduction performance of COF-Co1Zn2. This work shows that multi-site synergistic catalysis is an effective way to optimize the catalytic performance of COF catalysts for photochemical CO2 reduction.