Enhanced the Efficiency of Electrocatalytic CO₂ -to-CO Conversion by Cd Species Anchored into Metal-Organic Framework

Metal-organic frameworks (MOFs) as a promising platform for electrocatalytic CO₂ conversion are still restricted by the low efficiency or unsatisfied selectivity for desired products. Herein, zirconium-based porphyrinic MOF hollow nanotubes with Cd sites (Cd-PCN-222HTs) are reported for electrocatalytic CO₂ -to-CO conversion. The dispersed Cd species are anchored in PCN-222HTs and coordinated by N atoms of porphyrin structures. It is discovered that Cd-PCN-222HTs have glorious electrocatalytic activity for selective CO production in ionic liquid-water (H₂ O)-acetonitrile (MeCN) electrolyte. The CO Faradaic efficiency (FE_CO ) of >80% could be maintained in a wide potential range from -2.0 to -2.4 V versus Ag/Ag⁺ , and the maximum current density could reach 68.0 mA cm^-2 at -2.4 V versus Ag/Ag⁺ with a satisfied turnover frequency of 26 220 h^-1 . The enhanced efficiency of electrocatalytic CO₂ conversion of Cd-PCN-222HTs is closely related to its hollow structure, anchored Cd species, and good synergistic effect with electrolyte. The density functional theory calculations indicate that the dispersed Cd sites anchored in PCN-222HTs not only favor the formation of *COOH intermediate but also hinder the hydrogen evolution reaction, resulting in high activity of electrocatalytic CO₂ -to-CO conversion.