Large-Scale Facile Synthesis of Biomass Fibers and High-Entropy Metal Hierarchical Porous Carbon toward Enhanced Electromagnetic Absorption

The elevated dielectric properties of carbonized cotton fibers with refined conductive networks result in substantial impedance mismatch, severely compromising their electromagnetic wave (EMW) absorption performance. Using cotton fibers and [Zn(pz) 2 ] n complexes as easily prepared and low-cost raw materials, nano-hierarchically porous MnFeCuCe@C composites were constructed efficiently through optimization of the dynamic balance of element content and carbonization temperature. The results show that MnFeCuCe@C-20% exhibited a minimum reflection loss (RL min ) of −81.44 dB with a thickness of only 1.52 mm at an ultralow loading of 20 wt%, and the effective absorption bandwidth of MnFeCuCe@C-900 °C was also remarkably enlarged to 5.13 GHz at a thickness of 1.6 mm. Modifying only the metal content of the precursor and carbonization temperature can effectively reinforce the magnetic–dielectric synergy and impedance matching. The augmented EMW attenuation primarily stems from the inherent hierarchical porous structure of the MnFeCuCe@C nanocomposite and the rapid electron migration within its high-entropy metal particles. Furthermore, its excellent dissipation capability in practical application scenarios was demonstrated further through radar cross-section simulations. This work comprehensively delineates the optimization strategies for material dielectric properties as well as the convenient and environmental synthesis method.