Hydroxypillar[5]arene-Confined Silver Nanocatalyst for Selective Electrochemical Reduction of CO2 to Ethanol

CO is usually the dominant product on silver-based catalysts in electrochemical CO2 reduction reaction (CO2RR) possibly due to weak *CO adsorption. In this report, a hydroxypillar[5]arene-extended porous polymer-confined silver catalyst (PAF-PA5-Ag-0.8) for electrochemical CO2RR which can selectively produce ethanol with a maximum Faradaic efficiency of 55% at 11 mA cm(-1) is described. The study reveals that the hydroxypillar[5]arene-confined Ag clusters are the active sites for ethanol formation. Moreover, temperature-programmed desorption measurements demonstrate an enhanced adsorption strength of CO* on PAF-PA5-Ag-0.8 compared with that on commercial Ag nanoparticles, which is favored by the C-C coupling to form ethanol. The density functional theory study indicates that the confined Ag clusters in PAF-PA5-Ag-0.8 contribute to high C-2 selectivity in CO2RR through facilitating *COOH formation, stabilizing *CO intermediates, and inhibiting hydrogen evolution. This work provides a new design strategy by modulating *CO adsorption strength on non-copper electrocatalysts in converting CO2 into "green" C-2 products.