Asymmetric Cu−N1O3 Sites Coupling Atop-type and Bridge-type Adsorbed *C1 for Electrocatalytic CO2-to-C2 Conversion

Abstract

2D functional porous frameworks offer a platform for studying the structure–activity relationships during electrocatalytic CO₂ reduction reaction (CO₂RR). Yet challenges still exist to breakthrough key limitations on site configuration (typical M−O₄ or M−N₄ units) and product selectivity (common CO₂-to-CO conversion). Herein, a novel 2D metal–organic framework (MOF) with planar asymmetric N/O mixed coordinated Cu−N₁O₃ unit is constructed, labeled as BIT-119. When applied to CO₂RR, BIT-119 could reach a CO₂-to-C₂ conversion with C₂ partial current density ranging from 36.9 to 165.0 mA cm⁻² in flow cell. Compared to the typical symmetric Cu−O₄ units, asymmetric Cu−N₁O₃ units lead to the re-distribution of local electron structure, regulating the adsorption strength of several key adsorbates and the following catalytic selectivity. From experimental and theoretical analyses, Cu−N₁O₃ sites could simultaneously couple the atop-type (on Cu site) and bridge-type (on Cu−N site) adsorption of *C₁ species to reach the CO₂-to-C₂ conversion. This work broadens the feasible C−C coupling mechanism on 2D functional porous frameworks.