Bioinspired N4-metallomacrocycles for electrocatalytic oxygen reduction reaction

[Display omitted] •Summarizing the ORR features of bioinspired N4-metallomacrocycles.•Discussing the structural effects of N4-metallomacrocycles on ORR.•Summarizing immobilization methods for loading N4-metallomacrocycles on various supports.•Summarizing electrocatalytic ORR materials derived from N4-metallomacrocycles.•Discussing potential applications of N4-metallomacrocycles in new energy conversion techniques. Oxygen reduction reaction (ORR) is an important process involved in natural and artificial energy conversion schemes. As inspired by cytochrome c oxidases (CcOs), which are metalloenzymes catalyzing selective reduction of O2 to water at heme Fe porphyrin sites, metal macrocyclic complexes containing square-planar M−N4 coordination sites, such as metal porphyrins, corroles and phthalocyanines, have been extensively studied as catalysts and pre-catalysts for electrocatalytic ORR. This review addresses structural effects of these molecular metal macrocycles on the selectivity and activity of electrocatalytic ORR, including the effects of meso- and β-substituents, axial ligands, and second coordination spheres. In order to realize the practical use of molecular electrocatalysis, catalysts are required to be immobilized on appropriate supporting materials. Therefore, this review also addresses the effects of immobilization methods and interactions between molecular catalysts and supports on ORR. Moreover, the use of N4-metallomacrocycles and their derived materials in metal-air batteries is discussed, underlining the potential and promising applications of molecular electrocatalysis in new energy conversion techniques.