Bimetallic Metal–Organic Framework‐Derived Co/Co ₃ O ₄ @Carbon/Graphene Heterostructures for Efficient Microwave Absorption

Bimetallic MOF‐derived magnetic/carbon composites have shown great potential as lightweight microwave absorbers, while direct pyrolysis products still suffer from severe particle agglomeration and limited electromagnetic loss. Here, star‐shaped Co/Co ₃ O ₄ @carbon/graphene composites were fabricated via room‐temperature Co–Zn MOF synthesis followed by high‐temperature pyrolysis with incorporated graphene oxide. Structural characterization confirms that Co/Co ₃ O ₄ nanoparticles are uniformly anchored on crumpled reduced graphene sheets, fully inheriting the star‐shaped morphology of the parent MOF. Benefiting from the synergistic contribution of magnetic loss, dielectric loss, and conductive loss, the optimal S2 sample delivers a minimum reflection loss of −49.76 dB at a matching thickness of 1.88 mm, with an ultralow filler loading of only 17.5 wt.%. The corresponding effective absorption bandwidth reaches 5.44 GHz (12.56–18.00 GHz) at a matching thickness of 1.77 mm. The performance enhancement introduced by graphene can be attributed to the combined effect of multi‐interface polarization, continuous conductive loss, and optimized impedance matching.