Photo-Assisted Electrochemical CO2 Reduction to CH4 Using a Co-Porphyrin-Based Metal-Organic Framework

Metal-organic frameworks (MOFs) are a promising platform for assembling large concentrations of molecular catalysts on surfaces to drive the electroreduction of CO2. Yet until now, these MOF-based systems were shown to produce only 2-electron/proton products, i.e., CO or formic acid. Herein, it is demonstrated that a cobalt 5,10,15,20-tetra(4-carboxyphenyl) porphyrin (CoTCPP)-based MOF can produce significant quantities of an 8-electron/proton CH4, via a photo-assisted electrocatalytic approach. Specifically, detailed electrochemical and spectro-electrochemical analyses show that the addition of light illumination during electrocatalysis promotes the stabilization of a catalyst-bound CO intermediate, allowing its further reduction to the final product, CH4. Using the photo-assisted electrocatalysis method, maximum CH4 Faradaic efficiency of 14% was obtained at a low potential of -0.49 V-NHE. Hence, the presented concept provides an additional step toward the design of more efficient MOF-based electrocatalytic systems.