Rational construction of hierarchical Co@C@NPC nanocomposites derived from bimetallic hybrid ZIFs/biomass for boosting the microwave absorption

Abstract

Nowadays, electromagnetic (EM) radiation poses severe environmental pollution and harm to civilian and military life. To this end, it is urgent to synthesize high-efficiency microwave absorbers in terms of composition and structural design. Herein, we reported a unique hybrid nanostructure with Co particles embedded in hollow carbon polyhedron by a series of synthetic steps including carbonization and pyrolysis. Further, the nanoporous carbon (NPC) derived from wheat flour is coated onto the surface of Co@C polyhedrons, forming a special hierarchical structure (Co@C@NPC), which demonstrates outstanding microwave absorption properties due to the hierarchical porous structure, enhanced interfacial polarization, conduction loss, multi-reflection and matched impedance. Typically, with a 10 wt% filler content, the maximum RL of Co@C@NPC reaches −57.2 dB at 9.6 GHz and the corresponding effective bandwidth is 5.7 GHz (from 7.5 to 13.2 GHz) with an absorber thickness of 3 mm. Besides, the filler loading of 10 wt% is much lower than other reported bio-derived absorbers. In short, the hybrid zeolitic imidazolate frameworks offer a novel idea for constructing hollow carbon skeletons and introducing biomass carbon as a green, low cost and renewable material that enhances the dielectric loss and the synergistic effect between permittivity and permeability.