Excellent microwave absorption performance of polyphenol-metal coordination derived magnetic porous carbon spheres

Electromagnetic synergy and porous characteristics are two dominant factors in realizing light-weight and high-efficient microwave absorption performance. In this paper, a formaldehyde-assisted metal-ligand crosslinking strategy and a subsequent pyrolysis process are employed to synthesize magnetic porous carbon spheres with the electromagnetic synergy and porous characteristics, in which metal ions are tightly anchored in poly-(tannin acid) spheres because of the strong chelation coordination between them. The chemical composition of magnetic particles and the microwave absorption performance of the derived magnetic porous carbon spheres can be manipulated by adjusting the metal ions. Benefiting from the cooperative effects of porous structure, matched impedance, the electromagnetic synergistic enhancement between magnetic particles and carbon matrix, as well as the improved interfacial polarization caused by the large number of hetero-interfaces, both the microwave absorption intensity and the effective absorption bandwidths are significantly enhanced for magnetic porous carbon spheres, such as Co-PCSs and CoNi-PCSs, compared with PCSs. With 15 wt.% filler loading, the maximum reflection loss of CoNi-PCSs is −51 dB at 2.2 mm and the effective bandwidth is 7.2 GHz at 2.9 mm. Furthermore, this study provides the theoretical theory for the design and development of light-weight and highly efficient microwave absorption materials.