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.