Abstract: By rationally controlling the growth of zeolite-imidazolium salt skeleton (ZIF-67) nanoparticles on the hollow indium oxide (In₂O₃) and the subsequent pyrolysis process, In-Co-C hollow rod-like composites with multiple components were successfully prepared in this work. The synergistic impact of diverse components including In₂O₃, C, Co₃InC_0.75, and In not only optimizes impedance matching and improves conductive loss, but also creates significant interfacial polarization. Furthermore, the addition of Co source and pyrolysis temperature was found to have a significant affected on impedance matching and microwave absorption. The optimized In-Co-C sample displayed ultra-broad absorption bandwidth (EAB) of up to 7.12 GHz (10.88-18.0 GHz) at 2.26 mm thickness, which could cover the whole Ku band and part of X-band, outperforming the previously reported MOFs-derived composites. Furthermore, by adjusting the thickness to 2.91 mm and 4.01 mm, the EAB could cover the entire X band and most of the C band. The attenuation mechanisms were systematically investigated through the delta function method and ANSYS high-frequency structure simulator. These findings suggest that the MOFs-derived In-Co-C hollow nanorods could serve as high-performance microwave absorbers with ultra-broad absorption.

Key words: Microwave absorption, Hollow rod-like, MOFs-derived, Conductive loss, Interfacial polarization, Impedance matching