Copper-Based Metal-Organic Porous Materials for CO₂ Electrocatalytic Reduction to Alcohols

The electrocatalytic reduction of CO₂ has been investigated using four Cu-based metal-organic porous materials supported on gas diffusion electrodes, namely, (1) HKUST-1 metal-organic framework (MOF), [Cu₃ (μ₆ -C₉ H₃ O₆ )₂ ]_n ; (2) CuAdeAce MOF, [Cu₃ (μ₃ -C₅ H₄ N₅ )₂ ]_n ; (3) CuDTA mesoporous metal-organic aerogel (MOA), [Cu(μ-C₂ H₂ N₂ S₂ )]_n ; and (4) CuZnDTA MOA, [Cu_0.6 Zn_0.4 (μ-C₂ H₂ N₂ S₂ )]_n . The electrodes show relatively high surface areas, accessibilities, and exposure of the Cu catalytic centers as well as favorable electrocatalytic CO₂ reduction performance, that is, they have a high efficiency for the production of methanol and ethanol in the liquid phase. The maximum cumulative Faradaic efficiencies for CO₂ conversion at HKUST-1-, CuAdeAce-, CuDTA-, and CuZnDTA-based electrodes are 15.9, 1.2, 6, and 9.9 %, respectively, at a current density of 10 mA cm^-2 , an electrolyte-flow/area ratio of 3 mL min cm^-2 , and a gas-flow/area ratio of 20 mL min cm^-2 . We can correlate these observations with the structural features of the electrodes. Furthermore, HKUST-1- and CuZnDTA-based electrodes show stable electrocatalytic performance for 17 and 12 h, respectively.