Mechanistic Elucidations of Highly Dispersed Metalloporphyrin Metal‐Organic Framework Catalysts for CO2 Electroreduction. (18th January 2023)

• Record Type: Journal Article
• Authors: Smith, Michael R.; Martin, Clare B.; Arumuganainar, Sonia; Gilman, Ari; Koel, Bruce E.; Sarazen, Michele L.
• Is Part Of: Angewandte Chemie. Volume 135:Number 8(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-01-18
• Subjects: Electrocatalysis -- Immobilization -- Metal–Organic Framework -- Reaction Mechanism -- Spectroscopy; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.202218208
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: Immobilization of porphyrin complexes into crystalline metal–organic frameworks (MOFs) enables high exposure of porphyrin active sites for CO2 electroreduction. Herein, well‐dispersed iron‐porphyrin‐based MOF (PCN‐222(Fe)) on carbon‐based electrodes revealed optimal turnover frequencies for CO2 electroreduction to CO at 1 wt.% catalyst loading, beyond which the intrinsic catalyst activity declined due to CO2 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 CO2 electroreduction on PCN‐222(Fe) electrodes, which followed a shift from a rate‐limiting electron transfer to CO2 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 CO2 electroreduction mechanisms on PCN‐222(Fe) MOFs. Abstract : PCN‐222(Fe), a metalloporphyrin‐based metal–organic framework (MOF), was used for the CO2 electroreduction reaction. The proposed reaction mechanism necessitated catalyst weight loadings of 1 wt.% to mitigate obfuscations from mass transfer and in situ Raman spectroscopy confirmed the structural and reactive stability of the MOF under operating conditions.