Core–Shell Zeolitic Imidazolate Framework‐8@Zeolitic Imidazolate Framework‐67‐Derived Nitrogen‐Doped Porous Carbon Confined Co 3 O 4 Nanoparticle‐Embedded Polyhedron for High‐Performance Sodium–Air Batteries

Na–air batteries (SABs) have attracted increasing attention in recent years due to their high energy density and abundance of sodium resources. However, their application is still hindered by the lack of effective air cathodes capable of achieving stable and long cycle life. Herein, a transition metal oxide–carbon composite material in which Co 3 O 4 nanoparticles (NPs) are embedded in N‐doped carbon (NC) cages (NC@ Co 3 O 4 ), synthesized through a pyrolysis‐oxidation strategy derived from core–shell zeolitic imidazolate framework (ZIF)‐8@ZIF‐67, is reported. Benefiting from the synergistic effects between the highly active Co 3 O 4 NPs and the hollow NC cages, the NC@Co 3 O 4 composite exhibits outstanding bifunctional electrocatalytic performance. When employed as an air cathode in SABs, the NC@Co 3 O 4 catalyst delivers a high discharge capacity of 1385 mAh g −1 , a low overpotential gap of 0.44 V, and an ultralong cycling stability exceeding 250 cycles (500 h). The results presented here provide valuable insights into the rational design of high‐efficiency catalysts for rechargeable SABs.