Doubly Urea‐Bridged Face‐to‐Face Dinuclear Metalloporphyrins for Efficient Electrocatalytic CO2 Reduction in Aqueous Solutions

Doubly urea-bridged face-to-face dinuclear metalloporphyrins are synthesized for electrocatalytic CO₂ reduction in aqueous solutions. Dinuclear metalloporphyrins are more active than mononuclear analogues by displaying larger partial currents and smaller overpotentials for the CO production. It is shown that the superior electrocatalytic activity of dinuclear metalloporphyrins is a result of the collaboration between the two metalloporphyrin units.

Electrocatalytic CO₂ reduction reaction (CO₂RR) is involved in new energy conversion scheme. Although many electrocatalysts for CO₂RR have been developed, improving the activity and selectivity of molecular catalysts in aqueous solutions remains a challenge. Herein, the synthesis and electrocatalytic CO₂RR features of doubly urea-bridged face-to-face dinuclear metalloporphyrins 1-M (M = Co, Fe) are reported. By bridging two porphyrin units through two urea groups, 1-Co and 1-Fe with two porphyrin units arranged in a face-to-face manner are synthesized. Both complexes are active and selective for electrocatalytic CO₂-to-CO conversion in CO₂-saturated bicarbonate solutions, achieving >96.3% FE_CO for 1-Co and >93.8% FE_CO for 1-Fe. Importantly, 1-M is more active than mononuclear analogues 2-M and 3-M for electrocatalytic CO₂RR. The partial current for the CO production with 1-M is four times larger than that with 2-M and five times larger than that with 3-M. The CO₂RR overpotential with 1-M is smaller than that with 2-M and 3-M by more than 180 mV. These results suggest the collaboration between the two metalloporphyrin units for electrocatalytic CO₂RR. This work therefore is significant to present 1-M as active and selective CO₂RR electrocatalysts and to showcase the collaboration between two metalloporphyrin units in boosting CO₂RR catalysis.

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