Hydrophobic perfluoroalkane modified metal‐organic frameworks for the enhanced electrocatalytic reduction of CO2

Abstract The electrochemical reduction of CO 2 to value‐added chemicals would be an efficient way to utilize CO 2 and mitigate greenhouse gas emission. However, the associated competitive hydrogen evolution reaction (HER) in aqueous electrolytes usually leads to poor selectivity for the CO 2 electroreduction reactions (CO 2 RR). Due to their high specific surface areas and tunable single active sites, metal‐organic frameworks (MOFs) are considered as promising candidates for CO 2 RR. Herein, the Fe‐porphyrin based Zr‐MOF, PCN‐222(Fe), was treated with perfluorocarboxylic acid to afford the hydrophobic F n ‐PCN‐222(Fe) ( n = 5 and 7, n is the number of fluorine atoms in the perfluoroalkyl chain) for improving the selectivity CO 2 RR via inhibiting the HER. Owing to the single active Fe sites were positioned in a hydrophobic microenvironment, the optimal F 5 ‐PCN‐222(Fe) shows a high Faradic efficiency of 97% toward production of CO at −0.7 V versus reversible hydrogen electrode. Meanwhile, F 5 ‐PCN‐222(Fe) achieved a high turnover frequency value of 3850 h −1 at −0.8 V, which was almost 3.6 times higher than that of PCN‐222(Fe) and surpassed most of other reported MOFs. This study paves a new way to improve the selectivity of the CO 2 RR via inhibiting the associated HER by increasing the hydrophobicity of the electrocatalysts.