Transition metal macrocycles for heterogeneous electrochemical CO2 reduction

Electrochemical CO2 reduction reaction (CO2RR) represents a promising approach for converting CO2 to valuable chemical fuels and feedstocks, but its commercial viability is largely hindered by the lack of high-performance electrocatalyst materials. Among a number of candidates, transition metal macrocycles including phthalocyanines and porphyrins have attracted revived attention for their great potentials and structural/functional diversities. Here, we overview recent research advances on these macrocyclic materials for heterogeneous electrochemical CO2RR. It starts with a brief introduction about CO2RR fundamentals and current understanding of the reaction mechanism on transition metal macrocycles. Different strategies are then detailed with examples to show how to optimize their electrocatalytic performances. At the end, we summarize existing scientific challenges and analyze future prospects of this exciting field.