Tailoring dielectric-magnetic synergy in bimetallic MOF-derived Cu/C@Fe₃O₄ for high-efficiency electromagnetic wave absorption

Metal-organic framework (MOF)-derived materials have demonstrated significant potential as high-performance electromagnetic wave (EMW) absorbers. However, conventional monometallic MOF-derived absorbers suffer from limited tunability of electromagnetic parameters due to their reliance on single-metal components, which severely restricts performance optimization. Herein, we propose a MOFs-mediated competitive metal ion coordination strategy to rationally synthesize bimetallic Cu/Fe-MOF-derived EMW absorbers. By exploiting the competitive coordination behavior of Jahn-Teller-active Cu²⁺ (preferentially axially coordinating with N-rich ligands) and octahedrally favored Fe²⁺ (selectively binding to carboxylate ligands), spatial segregation of metal nodes and atomic-level interfacial engineering are achieved. Systematic modulation of the Cu/Fe precursor ratio enables precise control over the electronic state density and magnetic permeability of the derived composites, thereby synergistically optimizing impedance matching and attenuation efficiency. Remarkably, the equimolar Cu/Fe absorber (Cu1/C@Fe₃O₄-1) exhibits excellent EMW absorption performance, achieving a reflection loss of −44.00 dB (>99.99 % energy dissipation) with an ultrathin thickness of 1.65 mm and a wide effective absorption bandwidth (EAB) of 5.84 GHz at 1.70 mm. This work elucidates the structure-property relationships of bimetallic MOF-derived absorbers from the perspective of competitive coordination, establishing a theoretical paradigm for designing next-generation lightweight broadband EMW absorption materials.