Enhancement of Electrocatalytic CO₂ Reduction to Methane by CoTMPyP when Hosted in a 3D Covalent Graphene Framework

Electrocatalytic reduction of carbon dioxide is a promising technique to convert CO₂ into useful products and to aid environmental concerns. Here, we report on the preparation of a unique three-dimensional graphene-based structure, covalent graphene framework (CGF), which is obtained by the chemical attachment of a nitro-functionalized graphene derivative to a 3D aniline-based linker. CGF is then used to host cobalt [5,10,15,20-(tetra-N-methyl-4-pyridyl)porphyrin] (CoTMPyP) as a catalyst for electrochemical CO₂ reduction. The porous structure of CGF with free amine functional groups enables strong irreversible adsorption of CO₂ which promotes the formation and stabilization of a key carbamate intermediate. The combined CGF-CoTMPyP catalytic system shows enhanced performance for the 8e^- CO₂ reduction to CH₄ (faradaic efficiency ∼20%) at −0.72 V versus RHE in aqueous solutions. This work emphasizes the importance of tuning the morphology and chemical composition of the catalyst surroundings in the design of efficient catalytic systems in the field of energy conversion.