3D Cluster‐Based Covalent Organic Framework for Efficient CO₂ Photoreduction

Abstract Copper clusters exhibit superior catalytic activity for the CO 2 reduction reaction (CO 2 RR), and their defined structures endow them with unique advantages for modeling the catalytic mechanism at the atomic level. Additionally, the construction of highly stable and regularly structured covalent organic frameworks (COFs) based on copper clusters still presents significant challenges. Herein, we reported two highly stable and reactive cluster‐based COFs (termed Cu 4 COF‐1 and Cu 4 COF‐2) constructed via a stepwise assembly strategy. The epitaxially amino‐modified Cu 4 cluster (Cu 4 ‐ NH 2 ) was initially synthesized based on coordination bonds. Then, Cu 4 COFs were obtained by the covalent linkage of Cu 4 ‐ NH 2 clusters and organic linkers. Compared with isolated Cu 4 clusters, the Cu 4 COFs exhibit greater stability, a narrower band gap, a larger specific surface area, and better charge transfer ability, which endow them with superior photocatalytic CO 2 RR performance under visible light. In‐situ infrared spectroscopy and density functional theory (DFT) calculations revealed that the covalently linked Cu 4 COFs could efficiently lower the energy barrier for the formation of the critical *COOH intermediate, thereby enhancing the photocatalytic activity. This study offers a solid basis for the atomically precise construction of novel metal‐cluster‐based COF catalysts.