Mechanistic Elucidations of Highly Dispersed Metalloporphyrin Metal‐Organic Framework Catalysts for CO<sub>2</sub>Electroreduction
Michael Smith, Clare B. Martin, Sonia Arumuganainar, Ari Gilman, Bruce E. Koel, Michele L. Sarazen
Abstract
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.