Iron-Nitrogen Doped Porous Carbon Absorbers Constructed from Hyper-Crosslinked Ferrocene Polymers and Efficient Electromagnetic Wave Absorption

Herein, ferrocene and a nitrogen heterocyclic compound (melamine or imidazole) were hyper-crosslinked using an external crosslinker through a straightforward Friedel-Crafts reaction, resulting in the formation of nitrogen-containing hyper-crosslinked ferrocene polymer precursors (HCPs). Subsequently, these precursors were carbonized to yield iron-nitrogen doped porous carbon (Fe-NPCs) absorbers. The Fe-NPCs exhibit a distinctive porous structure comprising aggregated nanotubes and nanospheres, with the pore structure being adjustable through the modulation of Fe and N content. The strategy of constructing doped porous carbon from hyper-crosslinked metallocene ensures the uniform distribution of Fe and N within the skeleton. The catalytic effect of iron during carbonization further promotes the graphitization of the carbon skeleton and the formation of carbon nanotubes. Meanwhile, the formed active structures, such as Fe-NxC, N-dipole, and magnetic α-Fe, are uniformly distributed in the unique porous carbon skeleton. These are thought to lead to the efficient EMW absorption properties of Fe-NPCs. Among them, Fe-NPC-M2 prepared with a ferrocene/melamine molar ratio of 2/1, demonstrated strong loss capability (RLmin of -55.3 dB) and a wide absorption band (5.52 GHz) at a relatively thin matching thickness (1.9 mm). This study is the first to employ hyper-crosslinked polymers in the domain of wave absorption, and this novel strategy introduces novel ideas for the fabrication of porous carbon wave absorption materials.