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 ratelimiting electron transfer to CO 2 mass transfer as the potential increased from À 0.6 V to À 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.

Kinetic Impacts of Defect Sites in Metal–Organic Framework Catalysts under Varied Driving Forces

“…The porous nature of MOFs can improve the delivery of molecules or ions to electrode surfaces to circumvent the effects of mass transport limitations on catalysis-relevant current densities, and the modularity of linker functional groups can promote inductive or second coordination sphere intermediate stabilization to overcome intermediate scaling relationships for multi-electron redox processes . In these cases, the MOF acts as the active catalytic phase or as an auxiliary component that can utilize specific material properties (e.g., porosity or functional group proximity) to facilitate catalysis . Conversely, MOFs can act as scaffolds that reconstruct under potential bias (or external extreme thermal bias), resulting in MOF-derived metal or metal composite materials (e.g., oxides, phosphides, sulfides, etc.)…”

Rational Design of Advanced Metal Organic Framework‐Based Nanostructured Catalysts toward Electrocatalytic CO2 Conversion: A Mini Review

“…In this regard, ECO 2 R has been exploited extensively, but still is in its initial steps and requires further improvements to meet industrial demands. [ 3,4 ]…”

“…In this regard, ECO 2 R has been exploited extensively, but still is in its initial steps and requires further improvements to meet industrial demands. [3,4] Other energy resources such as wind, solar, and tidal energy suffer from intermittency which limits their further development to replace fossil fuels resources. [5] The ECO 2 R, which uses renewable electricity as input power, not only addresses CO 2 release into atmosphere but also it can mitigate energy demand through producing chemicals and fuels such as formate (HCOO À ), carbon monoxide (CO), ethanol (CH 3 CH 2 OH), methanol (CH 3 OH), ethylene (C 2 H 4 ), and so on.…”

Enhanced the Efficiency of Electrocatalytic CO2‐to‐CO Conversion by Cd Species Anchored into Metal‐Organic Framework

“…[ 28 ] The molecule catalyst of functionalized Fe‐porphyrin was also applied to generate an MOF (PCN‐222(Fe)), demonstrating that the optimal TOFs for electrocatalytic CO 2 ‐to‐CO conversion at 1 wt% catalyst loading. [ 29 ] The intrinsic catalyst activity reduced at other PCN‐222(Fe) loadings, resulting from CO 2 mass transport limitations. Besides, active metal sites (e.g., Co, Cu, and Au) were incorporated into the MOFs to form photo‐coupled electrocatalysts for electrocatalytic CO 2 ‐to‐CO conversion.…”