Fe-Regulated Coupled 2e-/4e- ORR Pathway in a Conductive Co-Fe HITP Framework for Rechargeable Zinc-Air Batteries.

Zinc-air batteries based on non-precious-metal catalysts are promising for sustainable energy conversion, yet their performance is hindered by sluggish oxygen reduction reaction (ORR) kinetics and limited understanding of pathway regulation in metal-organic framework (MOF)-based catalysts. Herein, we report a bimetallic electron-conductive Co-Fe framework based on 2,3,6,7,10,11-hexaiminotriphenylene (HITP), in which Fe incorporation shifts the ORR toward a greater four-electron contribution. Structural, electrochemical, and density functional theory (DFT) analyses reveal complementary dual-site roles: Co sites favor peroxide formation via the 2e- pathway, whereas Fe sites promote O─O bond activation and subsequent reduction of peroxide intermediates. Peroxide intermediates generated on Co sites can be further converted to OH- at Fe sites. As a result, the Co2.2Fe0.8(HITP)2 catalyst exhibits enhanced ORR activity and enables a rechargeable zinc-air battery with an open-circuit voltage of 1.37 V, a peak power density of 154.2 mW cm-2, and a high specific capacity of 843 mAh gZn -1 along with enhanced cycling stability. This work establishes electron-conductive MOFs as a well-defined platform for probing ORR mechanisms and highlights dual-metal site engineering as an effective strategy for modulating ORR pathways and improving electrocatalytic performance.