Advanced Zn–air batteries (ZABs) with ultrahigh cycle life, which also harness energy with bifunctional electrochemical reactions, are significantly challenging for the commercialization of hybrid/electric vehicles and wearable electronics. Herein, we demonstrated robust aqueous and flexible ZABs with novel three-dimensional dual-linked hexaiminobenzene metal–organic framework (Mn/Fe-HIB-MOF)-based bifunctional oxygen electrocatalysts and superionic functionalized bio-cellulose electrolytes (64 mS cm⁻¹). The well-defined quintet-shelled hollow sphere MOFs possess a hierarchical porous structure, excellent packing density with a surface area of 2298 m² g⁻¹, and chemical stability as compared to conventional MOFs. Mn/Fe-HIB-MOF exhibited superior bifunctional oxygen electrocatalytic activity (0.627 V) with half-wave potential (0.883 V) for oxygen reduction and overpotential (280 mV@10 mA cm⁻²) for oxygen evolution reactions, outperforming commercial Pt/C and RuO₂. Their favorable oxygen reactions and surface electronic structures were confirmed by density functional theory. Significantly, the Mn/Fe-HIB-MOF cathode demonstrated the highest lifetimes reported to date for rechargeable ZABs, namely 1000 h (0.75 V voltage gap@10 mA cm⁻²) over 6000 cycles and 600 h (efficiency ∼65.24%@25 mA cm⁻²) over 3600 cycles with excellent flexibility for liquid and all-solid-state flexible ZABs, respectively. These promising results illustrate the great potential of these novel hexaiminobenzene MOFs and superionic bio-cellulose membranes for the commercial implementation of rechargeable ZABs.

The future of electrochemical energy storage spotlights on the designed formation of highly efficient and robust bifunctional oxygen electrocatalysts that facilitate advanced rechargeable metal-air batteries. We introduce a scalable facile strategy for the construction of a hierarchical three-dimensional sulfur-modulated holey C₂N aerogels (S-C₂NA) as bifunctional catalysts for Zn-air and Li-O₂ batteries. The S-C₂NA exhibited ultrahigh surface area (∼1943 m² g^–1) and superb electrocatalytic activities with lowest reversible oxygen electrode index ∼0.65 V, outperforms the highly active bifunctional and commercial (Pt/C and RuO₂) catalysts. Density functional theory and experimental results reveal that the favorable electronic structure and atomic coordination of holey C–N skeleton enable the reversible oxygen reactions. The resulting Zn-air batteries with liquid electrolytes and the solid-state batteries with S-C₂NA air cathodes exhibit superb energy densities (958 and 862 Wh kg^–1), low charge–discharge polarizations, excellent reversibility, and ultralong cycling lives (750 and 460 h) than the commercial Pt/C+RuO₂ catalysts, respectively. Notably, Li-O₂ batteries with S-C₂NA demonstrated an outstanding specific capacity of ∼648.7 mA h g^–1 and reversible charge–discharge potentials over 200 cycles, illustrating great potential for commercial next-generation rechargeable power sources of flexible electronics.