High-Performance Electromagnetic Interference Shielding and Photothermal Superhydrophobicity Achieved by Nuclear Sheath Stacking in Three-Dimensional Honeycomb Structure and Multi-Level Heterogeneous Interfaces

The unpredictable and extremely cold weather conditions, combined with increasing electromagnetic pollution, have posed a serious threat to human health and socioeconomic well-being. However, existing deicing technologies and electromagnetic interference (EMI) materials lack adaptability to low-temperature, high-humidity environments. This study developed a lightweight asymmetric layered composite foam by integrating multilevel core–shell structures with heterogeneous core–shell fillers into a melamine foam (MF) matrix. Designed to leverage the differences in conductivity and dielectric constant between multiscale heterogeneous interfaces, this composite foam enhances the movement of free electrons and the relative displacement between electrons and atomic nuclei, thereby achieving efficient polarization and conduction losses. More than that, the unique feature of this composite lies in its ″absorption–absorption–reflection–reabsorption″ multilevel structure, enabling the composite to achieve an EMI shielding effectiveness of 70.7 dB in the X-band (8.2–12.4 GHz) and an absorption efficiency of 79.8%. Benefiting from the destructive interference of electromagnetic waves within the layered foam structure, the asymmetric composite foam (MHC-MNPF-ACN) exhibits superior absorption-dominated EMI shielding performance with excellent frequency selectivity. Additionally, by anchoring dual-size fillers onto the MF skeleton via impregnation adsorption to form a honeycomb-like 3D ″light-trapping″ network. This not only allows the composite foam to reach 93.6 °C under 1 sun, enabling rapid deicing within 160 s but also endows it with excellent superhydrophobicity and mechanical properties. These features provide a novel and multifunctional integrated approach to the fabrication of frequency-selective, absorption-dominated EMI shielding materials, proposing a new strategy for the protection of outdoor electromagnetic facilities in extremely low-temperature environments.