Controlling the Oxidation State of Copper in Metal-Organic Frameworks for CO Electroreduction to Acetate.

The electrochemical carbon monoxide reduction reaction (CORR) represents a promising approach for the conversion of CO into acetate. However, the efficiency and selectivity of CO-to-acetate conversion are hindered by the competing formation of other products. Here, a Cu-MFU-4l-F catalyst is reported that preserves mixed-valence Cu species through the introduction of halogens and a precise Cu─N3 coordination structure, facilitating efficient CORR with a Faradaic efficiency (FE) of 73.2% for acetate in a flow cell. Furthermore, the selectivity for acetate remained stable over 140 h in a membrane electrode assembly (MEA) electrolyzer. The X-ray absorption spectroscopy reveals that the coordination environment around Cu is retained during the catalysis. In situ ATR-FTIRS indicates that the introduction of fluorine enhanced surface *CO adsorption and key intermediate *OCCOH formation, facilitates asymmetric C─C coupling, and improves the selectivity for acetate.