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 CH4selectivity 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 CO2to CH4. The highest Faradaic efficiency of CH4reached 80.4% at a current density of −300 mA cm−2in 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−2at a potential of −1.23V versus reversible hydrogen electrode. Comprehensive experimental investigations revealed the Cu-PMOF electrode enabled a multi-step CO2hydrogenation process, characterized by effective H2O activation and the sequential transformation of CO2into crucial intermediates, ultimately leading to the selective formation of CH4.

The electrocatalytic reduction of carbon dioxide (CO₂) to methane (CHOSCO) is an effective way to achieve a sustainable carbon cycle. However, this makes a complex reaction process involving 8-electron transfer, which still faces great challenges in achieving efficient catalysis and selective methane generation in practical applications. In this paper, a simple solvothermal reaction strategy was used to anchor the copper atom (Cu) in the porphyrin-based metal-organic framework (PMOF), and a monatomic copper catalyst named Cu-PMOF was constructed. The Cu-PMOF electrode has a highly active Cu reaction site, optimal Cu loading and loose structure, which significantly enhances the electrocatalytic efficiency of the reduction of CO₂ to CH. In the 1 M potassium hydroxide electrolyte flow battery system, when the current density is ~ 300 mA · cm-2, the maximum Faraday efficiency of Cu-PMOF catalytic CH? generation can reach 80.4%. In addition, when the potential of the reversible hydrogen electrode is -1.23V, the maximum partial charge density of the Cu-PMOF electrode can reach -337.5mA · cm²². The above experimental results show that the Cu-PMOF electrode realizes the multi-step hydrogenation process of CO₂ and the final selective generation of CH? by efficiently activating H2O and gradually converting CO2 into key intermediates.

Journal: Green Chemistry

original link: https://pubs.rsc.org/en/content/articlelanding/2025/gc/d5gc02085a/unauth