Mechanistic Elucidations of Highly Dispersed Metalloporphyrin Metal‐Organic Framework Catalysts for CO2Electroreduction

Abstract Immobilization of porphyrin complexes into crystalline metal–organic frameworks (MOFs) enables high exposure of porphyrin active sites for CO 2 electroreduction. Herein, well‐dispersed iron‐porphyrin‐based MOF (PCN‐222(Fe)) on carbon‐based electrodes revealed optimal turnover frequencies for CO 2 electroreduction to CO at 1 wt.% catalyst loading, beyond which the intrinsic catalyst activity declined due to CO 2 mass transport limitations. In situ Raman suggested that PCN‐222(Fe) maintained its structure under electrochemical bias, permitting mechanistic investigations. These revealed a stepwise electron transfer‐proton transfer mechanism for CO 2 electroreduction on PCN‐222(Fe) electrodes, which followed a shift from a rate‐limiting electron transfer to CO 2 mass transfer as the potential increased from −0.6 V to −1.0 V vs. RHE. Our results demonstrate how intrinsic catalytic investigations and in situ spectroscopy are needed to elucidate CO 2 electroreduction mechanisms on PCN‐222(Fe) MOFs.