Cu Triatomic Sites Embedded COFs Enable Highly Selective CO ₂ Electroreduction to C ₂ H ₄

Abstract Cu‐based covalent organic framework (COF) catalysts with well‐defined and porous structures hold significant promise for CO 2 electroreduction reaction (CO 2 RR), while producing mainly simple C1 products. Designing Cu‐based COF catalysts targeting C2+ products are still challenging due to unfavorable C─C coupling on far‐located isolated Cu sites. Herein, vinylene‐linked metal‐covalent organic frameworks (MCOFs,Cu‐CTU+TMTT‐MCOF and Cu‐CTU+TMTP‐MCOF) catalysts with a well‐defined crystalline structure, high density, and symmetrical Cu triatomic coordination environment are elaborately constructed. The Cu‐CTU+TMTT‐MCOF demonstrated a remarkable CO 2 RR‐to‐C 2 H 4 faradaic efficiency (FE) of 51.9% and a current density of 360.1 mA cm −2 at the potential of −1.17 V versus reversible hydrogen electrode (RHE) in 1.0 m KOH solution. In situ Fourier transform infrared spectra and density functional theory studies revealed that the adjacent symmetric Cu site with a close distance in vinylene‐linked MCOFs can stabilize H 2 COH‐H 2 C * intermediates, thus improving the selectivity of C2 products. This study presents an innovative approach for constructing symmetrical Cu triatomic sites while offering critical guidance for advancing metal‐based COFs to enhance CO 2 RR‐to‐C 2 H 4 efficiency.