Impedance-matchable 3D MXene sponge/NiFe@NC heterostructure with tunable pores for efficient electromagnetic wave absorption and thermal resistance

The rapid advancement of 5G/6G communication and radar technology has exacerbated issues of electromagnetic wave (EMW) leakage, interference, and thermal management. Therefore, developing lightweight EMW absorbers that integrate strong absorption, broad bandwidth, and thermal stability is crucial. Herein, a 3D MXene sponge/NiFe@NC heterostructure with tunable pore architecture is constructed by pyrolyzing a polyurethane (PU) foam template uniformly coated with NiFe-decorated Ti3C2Tx MXene nanosheets. The resulting porous dielectric–magnetic network integrates interconnected MXene pathways with uniformly dispersed NiFe@NC nanoparticles, enabling a synergistic effect of dielectric–magnetic loss through conduction loss, dipole/interface polarization, and magnetic loss. Precise pore structure design enhances impedance matching and promotes multi-scattering and internal reflection of EMWs. Notably, an “EMW–pore matching” mechanism is proposed, whereby pore size governs the impedance matching at specific frequencies, enabling tunable absorption performance. The optimized absorber achieves a reflection loss (RL) of −67.84 dB, while radar cross-section (RCS) simulations confirm its exceptional attenuation and stealth potential. Additionally, the 3D skeleton derived from PU foam confers remarkable thermal resistance and flame retardancy. This pore-regulation strategy provides a scalable route to designing lightweight, broadband, and thermally stable EMW absorbers for next-generation communication and stealth applications.