Yolk–shell ZnO/C@air@CoNi nanocages derived from bimetallic MOFs for boosted electromagnetic wave absorption

The dielectric–magnetic synergy and interfacial engineering is an important methodology to boost electromagnetic wave absorption performance. We herein propose a novel “coating-ion exchange etching-high temperature carbonization” process to synthesize yolk–shell zinc oxide/carbon@air@cobalt-nickel alloy (ZnO/C@air@CoNi) nanocages by taking advantages of dielectric–magnetic synergy and interfacial effect. The bimetallic core–shell ZIF-8@ZIF-67 precursor is employed as the structural template while Ni(NO₃)₂·6H₂O as an etchant to ensure controlled ion-exchange etching. The resulting dielectric zinc oxide/carbon (ZnO/C) core promotes interfacial polarization and dipole reorientation losses, while the CoNi shell enhances conductive loss and magnetic loss. Thanks to the dielectric–magnetic synergy and interfacial effect, the ZnO/C@air@CoNi nanocomposite exhibits outstanding electromagnetic wave absorption performance, achieving a maximum reflection loss of −72.28 dB and an effective absorption bandwidth of 5.28 GHz (12.40 −17.68 GHz) at a low filler loading of 20 wt%. This work provides new ideas to design absorbers by leveraging the structural versatility of MOF-derived precursors.