Porphyrin-based metal–organic frameworks anchored with Cu species for highly efficient electrocatalytic CO2 reduction to CH4†

The electrocatalytic carbon dioxide (CO₂) reduction into methane (CH₄) represents a promising strategy for sustainable carbon cycling. Nevertheless, this complex conversion, involving an eight-electron transfer process, faces significant challenges in achieving satisfactory catalytic activity and CH₄ selectivity for practical applications. Herein, we employed a facile solvothermal reaction strategy to anchor copper (Cu) atoms in the porphyrin-based metal–organic framework (PMOF) to construct Cu single-atom catalysts, named the Cu-PMOF catalyst. The good combination of highly accessible Cu active sites, optimized Cu loading, and a loose structure in the Cu-PMOF electrode significantly enhanced the electrocatalytic performance for the conversion of CO₂ to CH₄. The highest Faradaic efficiency of CH₄ reached 80.4% at a current density of −300 mA cm⁻² in 1 M potassium hydroxide electrolytes with a flow cell configuration. Moreover, this Cu-PMOF electrode achieved a maximum partial current density of −337.5 mA cm⁻² at a potential of −1.23 V versus reversible hydrogen electrode. Comprehensive experimental investigations revealed the Cu-PMOF electrode enabled a multi-step CO₂ hydrogenation process, characterized by effective H₂O activation and the sequential transformation of CO₂ into crucial intermediates, ultimately leading to the selective formation of CH₄.