MOF-derived nanoporous carbon/Co/Co₃O₄/CNTs/RGO composite with hierarchical structure as a high-efficiency electromagnetic wave absorber

Lightweight and high-efficiency electromagnetic (EM) wave absorption are two key factors in the research of new-type absorbers, which could be obtained by regulating the component, structure, or suitable impedance matching. In this paper, a nanoporous carbon/Co/Co₃O₄/carbon nanotubes (CNTs)/reduced graphene oxide (RGO) composite with polyhedral structure was prepared by high-temperature pyrolysis of Co-based zeolitic imidazolate frameworks (ZIF 67). The carbon/Co/Co₃O₄/CNTs/RGO composite was composed of carbon polyhedrons, in which Co and Co₃O₄ particles were encapsulated by carbon polyhedrons and CNTs. With a filler ratio of 20 wt%, this absorber displayed the highest reflection loss (R_L) of −59.2 dB at 11.2 GHz with 2.5 mm thickness and the absorption bandwidth (R_L exceeding −10 dB) of 5.7 GHz (12.3–18 GHz) with a thickness of only 2 mm. The outstanding microwave absorption performance of this material results from proper impedance matching, synergistic effect, enhanced interfacial polarizations and interior cavities. This strategy may provide guidance for the manufacture of new-type absorbers with high-efficiency characteristics.