Biomass fibrous materials, as sustainable raw materials, were utilized widely for the fabrication of lightweight functional materials. Carbon materials derived from biomass retain natural morphological characteristics, and properties such as porous structure, low density, high specific surface area, and abundant delocalized π electrons endow the composite materials with excellent flexibility and scalability. However, the abundant electron transport pathways on the surface of its derived carbon fibers lead to severe impedance mismatch, causing a large portion of incident electromagnetic waves to be reflected rather than absorbed, which limits their application in electromagnetic wave absorption.
Strategically designing heterostructures incorporating highentropy metal particles and carbon fibers can enhance the defect density within carbon fibers, which enhances the boosted polarization relaxation effects within composite materials. Traditional synthesis methods primarily rely on hydrothermal processes and laser-assisted synthesis, which are complex and yield low amounts of raw materials. Moreover, the controllable design of metal-carbon materials with magneto-electric synergistic effects based on natural fiber substrates remains highly challenging. Therefore, there is an urgent need to develop a green, pollution-free, low-cost, and simple synthetic strategy.

Research Progress
1D [Zn(pz)₂]ₙ complexes can, using deionized water as the solvent, rapidly grow on the surface of biomass-derived cotton fibers at room temperature. These complexes act as intermediate linkers to uniformly anchor multi-element metals onto the cotton fiber surface. Subsequently, The MnFeCuCe@C nanocomposite was obtained through pyrolysis processes. Notably, the MnFeCuCe@C composite retains the original hollow-fiber morphology and develops abundant defect states along with additional magnetic components. This structural evolution facilitates efficient electromagnetic wave (EMW) penetration into the material matrix, enabling their substantial dissipation through magneto-electric synergistic effects (Figure 1). Structural characterization via Raman spectroscopy, adsorption tests, Fourier-transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) confirms the successful fabrication of the MnFeCuCe@C composite and validates the feasibility of the electromagnetic tuning strategy (Figure 2).

To address the impedance mismatch issue primarily caused by the intrinsically high dielectric behavior of carbon fibers, magnetic components were introduced, effectively suppressing the dielectric parameters of the MnFeCuCe@C composite. High-entropy metal particles disrupt the internal charge distribution equilibrium within the material, this inhomogeneous charge distribution induces the oriented alignment of dipoles, resulting in dielectric characteristics analogous to interfacial polarization. And this feature facilitates a balanced allocation between dielectric and magnetic loss mechanisms in the MnFeCuCe@C composite (Figure 3). Furthermore, to gain deeper insight into the key factors governing the tailored electromagnetic response, the research team investigated the influence of calcination temperature on the EMW absorption performance of the MnFeCuCe@C composite. The study revealed that calcination temperature affects the diffusion and aggregation of metal atoms, thereby enhancing dipole formation around defect sites. Meanwhile, multiple polarization relaxation mechanisms in the MnFeCuCe@C composite were activated, leading to additional Cole–Cole semicircles and prolonged polarization relaxation times (Figure 4).

Finally, the team employed radar cross-section (RCS) simulation software to evaluate the electromagnetic performance of the MnFeCuCe@C. The curves for MnFeCuCe@C-900°C and MnFeCuCe@C-1000°C exhibit greater stability. MnFeCuCe@C-1000°C achieves its maximum RCS reduction (31.72 dBm²) at 15°, while MnFeCuCe@C-900°C peaks (15.14 dBm²) at 0° (Figure 5), demonstrating excellent electromagnetic attenuation performance, which makes them suitable for complex radar detection scenarios with diverse far-field emission bands.

Future Prospects
An ultra-facile in situ approach facilitated the growth of [Zn(pz)₂]n complexes onto the surface of cotton fibers. Through optimization of the dynamic balance of element content and carbonization temperature, high-entropy metal particles effectively resolved impedance mismatch in carbon fiber matrices, meanwhile, in-depth investigation of the linkage relationship between microstructure and EM parameters revealed that the magnetic-dielectric synergy within MnFeCuCe nanoparticles and at MnFeCuCe/C heterointerfaces constitutes the determining factors for high-performance EMW absorption. Furthermore, radar cross-section (RCS) simulation verified the practical applicability of the absorber. From an industrial development perspective, its rapid synthesis, environmental benignity, and cost efficiency underscore significant potential for EMW absorption applications, providing profound insights for designing advanced electromagnetic absorbers.

Keywords
high-entropy metal particles, dielectric properties, magnetic-dielectric synergy, impedance matching, biomass carbon fiber

The complete study is accessible via DOI:10.34133/research.0868