Copper–Carbon Bond Metal–Organic Frameworks for Highly Efficient and Stable CO₂ Electrochemical Methanation

Cu-based metal-organic frameworks (Cu-MOFs) integrate the high tunability of molecular systems with the high activity of metal sites, making them promising electrocatalysts for the electrocatalytic reduction of carbon dioxide (CO₂RR). To date, the primary challenge in the application of Cu-MOFs in electrocatalytic CO₂RR is their poor stability during the reduction process. Herein, we pursue experimental and theoretical insights into Cu-C MOFs for the CO₂RR for the first time. Notably, Cu-TEPT, a Cu-C MOF synthesized through the reaction of tetrakis(acetonitrile)copper(I) Trifluoromethanesulfonate with 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine (TEPT) ligand, exhibited remarkable activity toward methane (CH₄) production. It achieved a high Faradaic efficiency (FE) of 83.6% and a CH₄ partial current density of up to 295.4 mA cm^-2, marking one of the highest performances reported to date. Experimental and theoretical studies indicated that the outstanding CO₂RR performance and stability of Cu-TEPT result from the ligand-protected alkynyl Cu(I) sites in Cu-TEPT, which effectively stabilize the Cu⁺ sites and accelerate the kinetics of CO₂ to CH₄.