Less-Coordinated Atomic Copper-Dimer Boosted Carbon-Carbon Coupling During Electrochemical CO₂ Reduction

This work reports a metal-organic framework (MOF) with less-coordinated copper dimers, which displays excellent electrochemical CO₂ reduction (eCO₂ RR) performance with an advantageous current density of 0.9 A cm^-2 and a high Faradaic efficiency of 71% to C₂ products. In comparison with MOF with Cu monomers that are present as Cu₁ O₄ with a coordination number of 3.8 ± 0.2, Cu dimers exist as O₃ Cu₁ ···Cu₂ O₂ with a coordination number of 2.8 ± 0.1. In situ characterizations together with theoretical calculations reveal that two *CO intermediates are stably adsorbed on each site of less-coordinated Cu dimers, which favors later dimerization via a key intermediate of *CH₂ CHO. The highly unsaturated dual-atomic Cu provides large-quantity and high-quality actives sites for carbon-carbon coupling, achieving the optimal trade-off between activity and selectivity of eCO₂ RR to C₂ products.