Rational Ligand-Mediated Microenvironment Regulation in Trinuclear Cu-Based Metal-Covalent Organic Frameworks for Enhanced Electrocatalytic CO Reduction

Electrochemical CO reduction (eCORR) is a promising route to high-value multicarbon products, yet its performance is fundamentally constrained by two intrinsic bottlenecks: insufficient CO surface coverage and sluggish C─C coupling kinetics. Herein, via a ligand engineering strategy, we construct synergistic centers for in-situ CO enrichment and conversion by conducting Schiff-base condensation between trinuclear cuprous clusters and organic units featuring sp²-hybridized nitrogen centers, successfully synthesizing Cu(I)-based two-dimensional metal-covalent organic frameworks (Cu-TAPA). At a current density of 100 mA cm⁻², Cu-TAPA achieves a Faradaic efficiency of 81.28% toward C₂ products, representing state-of-the-art performance. Experimental and theoretical investigations collectively demonstrate that the polar nitrogen sites of TAPA ligands pre-enrich CO molecules through electrostatic interactions, creating a microenvironment with a high local CO concentration; the enriched CO is subsequently transferred to copper catalytic sites, substantially lowering the C─C coupling energy barrier and thereby enhancing C₂ selectivity. This study proposes, at the atomic level, a new paradigm of ligand-mediated “in-situ CO enrichment-conversion” for catalyst design, providing a general strategy for the precise construction of efficient eCORR catalysts.