One-dimensional phenanthroline-based covalent organic framework bearing single cobalt atoms for efficient photocatalytic CO2 reduction

Metalated covalent organic frameworks (COFs) for 2D and 3D topologies are continuously being developed, whereas metalated COFs with 1D topologies are still in their infancy. Here, a novel 1D phenanthroline-based COF containing 4,4-(1,10-phenanthroline-2,9-diyl)bis[benzaldehyde] (PBA) is reported (PAD-COF). Subsequently, a metalated 1D COF, Co SAS/PAD-COF, is constructed using the bidentate ligand properties of PBA and anchoring the single Co atoms in PAD-COF through a post-synthetic modification strategy. This complex significantly improved the photocatalytic performance of PAD-COF, and the CO yield of the optimized Co SAS/PAD-COF was stable at 3091 µmol g⁻¹ h⁻¹ with a selectivity of 93%, which is approximately 43.7 times that of the original PAD-COF. Experimental and theoretical results demonstrate the excellent CO₂ photoreduction activity of Co SAS/PAD-COF owing to the synergistic effect of single Co catalytic sites and PAD-COF. Among them, PAD-COF, as the host, adsorbs CO₂ molecules and loads single Co atoms. Meanwhile, Co atoms function as catalytic sites and promote the adsorption and activation of CO₂, while reducing the reaction energy barrier formed by the *COOH intermediates. Therefore, this unique metalated 1D COF provides a fresh approach to photocatalytic CO₂ reduction.