Enhanced microwave absorption performance of porous and hollow CoNi@C microspheres with controlled component and morphology

Microwave absorbers with broadband absorption and lightweight features are highly desirable in electromagnetic interference and pollution treatment. Here, porous and hollow CoNi@C (CNC) microspheres derived from metal-organic frameworks (MOFs) are fabricated by a facile solvothermal route and subsequent annealing process. The morphology, structure, microwave absorption properties and their internal relationship are systematically investigated. For the porous and hollow CNC microspheres, the minimum RL can reach −44.8 dB at 10.7 GHz and the ultra-wide effective absorption bandwidth can reach up to 13.3 GHz (4.7–18.0 GHz) within the thickness of 1.6–4.0 mm. The CNC microspheres exhibit superior microwave absorption performance, attributing to the improved impedance matching and attenuation ability. The hollow structure, interfacial polarization, the synergistic effect between CoNi alloy and graphitized carbon simultaneously account for the microwave absorption mechanisms. Therefore, the present work provides the promising options on the design and preparation of lightweight and high-efficient microwave absorber with tunable component and specific morphology.