Unique Single‐Copper Metal−Organic Framework Enables Highly Selective Electrocatalytic CO ₂ Reduction to Ethylene via Asymmetric Coupling

ABSTRACT The prevailing paradigm in electrocatalytic CO ₂ reduction asserts that multinuclear copper are indispensable for facilitating C−C coupling, whereas isolated single‐copper sites in MOFs are considered inefficient for C ₂₊ production. Herein, we challenge this wisdom using two Cu−MOFs from the same ligand: CuTTB‐1 featuring isolated single copper sites and CuTTB‐2 possessing multinuclear copper. Counterintuitively, CuTTB‐1 achieved a Faradaic efficiency (FE) of ethylene production comparable to that of CuTTB‐2, along with a superior partial current density across both alkaline and acidic electrolytes. Remarkably, CuTTB‐1 delivered an exceptional FE(C ₂ H ₄ ) of 47.4% with a high partial current density of −142.2 mA cm ⁻² at an applied potential of −1.3 V vs . RHE and the corresponding overpotential of 1.38 V in acidic medium, surpassing all reported MOFs‐based catalysts and rivaling the performance of state‐of‐the‐art catalysts. Density functional theory calculations combined with operando infrared spectra revealed that ^* CO intermediate generated on an isolated copper site in CuTTB‐1 can desorb and migrate to a distant ^* CHO species, enabling asymmetric C−C coupling. This newly identified mechanism exhibits a substantially lower free energy compared to conventional symmetric coupling in CuTTB‐2. This work redefines the design principles for single‐site catalysts by demonstrating the viability of asymmetric coupling via reactant migration.