Central site regulation of cobalt porphyrin conjugated polymer to give highly active and selective CO2 reduction to CO in aqueous solution

Energetic catalyst for electrochemical CO2 conversion into high value-added chemicals is critical. Herein, an ethynyl-linked cobalt(II) porphyrin conjugated polymer (PCP) is decorated on the carbon nanotubes (CNTs) to fabricate bi-metallic central electrocatalyst (CoCoPCP/CNTs) for electrochemical CO2 reduction (CO2 RR). By regulating the porphyrins' central sites of the PCP, the resultant CoCoPCP/CNTs performs a high CO faradic efficiency of 94 % with a TOF of 2.4 s-1 at an extremely low overpotential of 0.44 V, which are much better than that of its CNTs-containing analogues. The effects of central site on the electrocatalytic performance and its mechanism are discussed based on the experimental study and theoretical calculation, and it is found that both of the Co centers in the four- and two-linked porphyrin units of the CoCoPCP are critical for CO2 RR. The present work should be of significance for the exploration of porphyrin-based conjugated polymers as energetic electrocatalyst in CO2 reduction.