Metal-organic framework-derived lilac flower-like CoNiZnO@nitrogen-doped carbon composites via a trapping microwave strategy for efficient absorption

The rapid development of technology has resulted in increased electromagnetic radiation, causing significant impact on human health. Metal-organic framework (MOF)-derived materials are extremely potential microwave absorbing materials with light weight and adjustable components. However, the interface loss and electromagnetic parameters of single metal-based MOF-derived composites are limited. Furthermore, it is difficult to achieve effective microwave absorption. Lilac flower-like CoNiZnO@nitrogen-doped carbon (NC) derived from CoNiZn MOFs were constructed by self-assembly and pyrolysis. The nitrogen-doped carbon and magnetic alloy (CoNi) in CoNiZnO@NC exhibited excellent dielectric loss and magnetic loss. Moreover, vaporization of Zn metal is beneficial to the formation of nanopores on the surface of the composites, so that microwave can enter the composites and optimize impedance matching. In addition, the presence of residual ZnO provides more heterogeneous interfaces. The effectively designed lilac flower-like structure enables microwave to enter the composites from multiple angles. This increases the multiple reflections and scattering of microwave, thereby trapping the microwave and improving microwave absorption performance. The minimum reflection loss reaches -70.70 dB at 11.04 GHz with 2.17 mm, and the effective absorption bandwidth reaches 4.48 GHz (13.52-18.00 GHz) at 1.55 mm, covering most of the Ku band. This work provides inspiration for the development and design of MOF-based microwave absorbing materials.