Porous carbon polyhedrons coupled with bimetallic CoNi alloys for frequency selective wave absorption at ultralow filler loading

Combining suitable microstructure and dielectric-magnetic synergy effect is conducive to achieve lightweight, broadband, and high-efficiency microwave absorbing materials within low filler loading. Herein, porous carbon polyhedrons coupled with bimetallic CoNi alloys were synthesized by using metal-organic frameworks (MOFs) as a template and subsequent pyrolysis treatment. Electromagnetic analysis indicated that the existence of metal Ni element could influence the wave attenuation capacity effectively, resulting in frequency selective wave absorption performance. Additionally, the pyrolysis temperature was also closely related to wave absorption intensity. The Co₂Ni₁/C/PVDF composites calcined at 800 °C possessed outstanding wave absorption performance at an ultra-low filler loading of 5 wt%. The minimum reflection loss value achieved -52 dB (10.8 GHz) under the matched thickness of 3 mm. Moreover, the broadest effective absorption bandwidth (RL< -10 dB) reached 6.2 dB (11.8–18 GHz) for Co/C-800/PVDF composites when the thickness turned into 2 mm. The remarkable wave attenuation ability was mainly ascribed to magnetic and dielectric loss, impedance matching as well as porous structure effect.