A multi-layer core-shell structure CoFeO@FeC@NiO composite with high broadband electromagnetic wave-absorption performance.

Enhancing the absorption strength of electromagnetic waves and broadening the absorption band are constant goals in designing and preparing absorbing materials. The use of composites has shown to be a very efficient method for acquiring broadband-absorbing materials, while the construction of a core-shell structure has demonstrated a significant enhancement in absorption capability. In this paper, the nanocomposite metal-organic framework (MOF) derivative CoFeO@C with a double core-shell structure and the nanocomposite MOF derivative CoFeO@FeC@NiO with a three-layered core-shell structure have been prepared using a chemical compound. The multi-layer structure provides more active sites for the multiple reflection and scattering of electromagnetic waves, effectively improving the attenuation capability. The effective absorption band (EAB) (reflection loss (RL) ≤ -5 dB) of both CoFeO@C and CoFeO@FeC@NiO are broadened compared to that of the ZIF-67 derivative. In particular, the minimum reflection loss (RL) of CoFeO@C was -52.7 dB at 13.3 GHz and 2.04 mm, and the EAB (RL ≤ -5 dB) is as wide as 9.35 GHz. Compared with the ZIF-67 derivative, the EAB exhibits a twofold rise, accompanied by a corresponding thickness increase of just 0.24 mm. At a matched thickness of 2.2 mm, the EAB of CoFeO@FeC@NiO can even reach 11.9 GHz.