A novel π-d conjugated cobalt tetraaza[14]annulene based atomically dispersed electrocatalyst for efficient CO2 reduction

Tetraaza[14]annulenes (TAA) are synthetic macrocycles which are analogue to porphyrins. However, there are almost no reports about the synthesis of polymers based on TAA and neither on their use as electrocatalysts. The study of new catalysts to promote an efficient electrochemical conversion of carbon dioxide to valuable chemicals is a promising approach to relieve the pressure of carbon emissions and realize the carbon cycle. Herein, we first report the synthesis of a novel tetraaza[14]annulene (TAA) based organic polymeric metal complex (PMC) by a non-template method. This PMC is used as ligand to construct a π-d conjugated cobalt coordination polymer (Poly-TAA-Co) with CoN4 structure which is supported on multi-wall carbon nanotubes (CNTs) to work as an atomically dispersed efficient electrocatalyst for the CO2 reduction reaction (CO2RR). The resulting catalyst (Poly-TAA-Co-CNT) exhibits excellent performance, with a 90% CO faradaic efficiency, a low overpotential (390 mV) and good stability in 0.5 M KHCO3 aqueous solution. Density functional theory calculations confirmed that the cobalt tetra[14]annulene is an excellent active site for electrocatalytic CO2RR. This work not only inspires the design of novel TAA based macromolecules, but also paves the way to the development and application of new molecular-based catalysts for electrocatalytic CO2RR.