Electro-reduction of carbon dioxide at low over-potential at a metal-organic framework decorated cathode

Electrochemical reduction of carbon dioxide is a clean and attractive strategy for producing organic products but is hindered by the high negative potential required to activate CO₂. The authors report a copper electrode decorated with a porous metal–organic framework, [Cu₂(L)] (H₄L = 4,4',4",4''-(1,4-phenylenebis(pyridine-4,2,6-triyl))tetrabenzoic acid), prepared by ionic-liquid-templated electrosynthesis. This decorated electrode exhibits an onset potential of −1.45 V vs. Ag/Ag⁺ for CO₂ reduction to formic acid in an organic electrolyte, achieving a current density of 65.8 mA·cm⁻² at −1.8 V with a Faradaic efficiency of 90.5% to formic acid. EPR spectroscopy confirms the presence of structural defects comprising homogenously distributed, uncoupled Cu(II) centers generated by the templated electro-synthesis. These active sites promote catalytic performance, as supported by DFT calculations.