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

Abstract

Abstract The electrochemical reduction of CO2 to value‐added chemicals would be an efficient way to utilize CO2 and mitigate greenhouse gas emission. However, the associated competitive hydrogen evolution reaction (HER) in aqueous electrolytes usually leads to poor selectivity for the CO2 electroreduction reactions (CO2RR). Due to their high specific surface areas and tunable single active sites, metal‐organic frameworks (MOFs) are considered as promising candidates for CO2RR. Herein, the Fe‐porphyrin based Zr‐MOF, PCN‐222(Fe), was treated with perfluorocarboxylic acid to afford the hydrophobic Fn‐PCN‐222(Fe) (n = 5 and 7, n is the number of fluorine atoms in the perfluoroalkyl chain) for improving the selectivity CO2RR via inhibiting the HER. Owing to the single active Fe sites were positioned in a hydrophobic microenvironment, the optimal F5‐PCN‐222(Fe) shows a high Faradic efficiency of 97% toward production of CO at −0.7 V versus reversible hydrogen electrode. Meanwhile, F5‐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 CO2RR via inhibiting the associated HER by increasing the hydrophobicity of the electrocatalysts.

Keywords

• CO
• CO2 electrocatalysis
• hydrophobicity
• metal‐organic framework
• perfluoroalkyl chain