Covalent Organic Framework Ionomer Steering the CO 2 Electroreduction Pathway on Cu at Industrial-Grade Current Density.

CO 2 electroreduction holds great promise for addressing global energy and sustainability challenges. Copper (Cu) shows great potential for effective conversion of CO 2 toward specific value-added and/or high-energy-density products. However, its limitation lies in relatively low product selectivity. Herein, we present that the CO 2 reduction reaction (CO 2 RR) pathway on commercially available Cu can be rationally steered by modulating the microenvironment in the vicinity of the Cu surface with two-dimensional sulfonated covalent organic framework nanosheet (COF-NS)-based ionomers. Specifically, the selectivity toward methane (CH 4 ) can be enhanced to more than 60% with the total current density up to 500 mA cm -2 in flow cells in both acidic (pH = 2) and alkaline (pH = 14) electrolytes. The COF-NS, characterized by abundant apertures, can promote the accumulation of CO 2 and K + near the catalyst surface, alter the adsorption energy and surface coverage of *CO, facilitate the dissociation of H 2 O, and finally modulate the reaction pathway for the CO 2 RR. Our approach demonstrates the rational modulation of reaction interfaces for the CO 2 RR utilizing porous open framework ionomers, showcasing their potential practical applications.