Doubly Urea-Bridged Face-to-Face Dinuclear Metalloporphyrins for Efficient Electrocatalytic CO₂ Reduction in Aqueous...

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.