Volume 62, Issue 8 e202218208
Research Article

Mechanistic Elucidations of Highly Dispersed Metalloporphyrin Metal-Organic Framework Catalysts for CO2 Electroreduction

Michael R. Smith

Michael R. Smith

Department of Chemistry, Princeton University, Princeton, NJ 08544 USA

These authors contributed equally to this work.

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Clare B. Martin

Clare B. Martin

Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544 USA

These authors contributed equally to this work.

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Sonia Arumuganainar

Sonia Arumuganainar

Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544 USA

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Ari Gilman

Ari Gilman

Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544 USA

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Bruce E. Koel

Bruce E. Koel

Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544 USA

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Michele L. Sarazen

Corresponding Author

Michele L. Sarazen

Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544 USA

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First published: 30 December 2022
Citations: 14

Graphical 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.

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.

Conflict of interest

The authors declare no conflict of interest.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

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