Core-shell Ni@C encapsulated by N-doped carbon derived from nickel-organic polymer coordination composites with enhanced microwave absorption

Metal-organic frameworks derived composites have been widely used as absorbers, however, low specific surface area and high filler loading still remain the great challenges for their practical applications. Herein, a coordination assembly strategy is developed for the formation of Ni2+-organic polymer coordination composites by the strong chelating ability, then a series of composites composed of core-shell Ni@C encapsulated by N-doped carbon (Ni@C/NC) have been synthesized by a subsequent pyrolysis process. Electromagnetic analysis indicates that increasing the amount of NiCl2 favors the formation of larger Ni particles, resulting in enhanced conductive and magnetic loss, but leads to decreased dipolar and interfacial polarization. Balancing the above mechanism, for Ni@C/NC-0.5with a specific surface area of 441.2 m2 g−1 and 20 wt% filler loading, a minimum reflection loss of −65.1 dB is achieved at 3.5 mm and the effective bandwidth reaches as wide as 8.6 GHz at 2.5 mm, covering the whole Ku band and 65% of X band, the unexceptionable attenuation capacity is attributed to the matched impedance, enhanced dipolar/interfacial polarization as well as multiple scattering. Furthermore, our strategy provides a novel guidance to the development of dielectric-magnetic composites in the application of lightweight and efficient microwave absorbers. [Display omitted]