PB@COF-derived core–shell Fe/Fe3O4/C composites with excellent electromagnetic wave absorption performance for the entire Ku band

Developing advanced electromagnetic wave absorption (EMWA) materials is crucial for curbing electromagnetic pollution. This study presents the synthesis of core–shell Fe/Fe 3 O 4 /C composites, FFC-700 and FFC-800, derived from Prussian blue@covalent organic framework (PB@COF) via pyrolysis at 700 and 800 °C, and the hollow FFC-900 at 900 °C. Their chemical compositions, microstructures, and EMWA performances were thoroughly examined. FFC-700 and FFC-800, featuring core–shell structures and abundant interfaces, facilitate electron transfer and enhance polarization effects. Notably, FFC-700 achieved a minimum reflection loss (RL min ) of − 75.82 dB at an ultrathin thickness of 1.45 mm, with an effective absorption bandwidth (EAB) of 6.22 GHz at 1.66 mm, spanning the entire Ku-band. FFC-800 also provides substantial EMWA performance, with an RL min of − 30.14 dB at 1.61 mm and an EAB of 6.08 GHz at 1.67 mm, also covering the Ku-band. Radar cross-section (RCS) simulations reveal the absorbers’ exceptional radar stealth, with their coatings significantly reducing RCS values. The composites’ adjustable structure, balanced composition, and dielectric-magnetic synergy optimize impedance matching for full-Ku-band coverage. This work offers a promising approach to fabricating efficient EMWA materials from PBA@COF and MOF@COF precursors.