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

Copper clusters exhibit superior catalytic activity for the CO₂ reduction reaction (CO₂RR), 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 Cu₄COF-1 and Cu₄COF-2) constructed via a stepwise assembly strategy. The epitaxially amino-modified Cu₄ cluster (Cu₄-NH₂) was initially synthesized based on coordination bonds. Then, Cu₄COFs were obtained by the covalent linkage of Cu₄-NH₂ clusters and organic linkers. Compared with isolated Cu₄ clusters, the Cu₄COFs exhibit greater stability, a narrower band gap, a larger specific surface area, and better charge transfer ability, which endow them with superior photocatalytic CO₂RR performance under visible light. In-situ infrared spectroscopy and density functional theory (DFT) calculations revealed that the covalently linked Cu₄COFs 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.