Lightweight MXene@Kapok Pulp/Nanofiber Composite Material for Electromagnetic Interference Shielding, Low Frequency Sound Absorption, and Thermal Insulation.

To meet the urgent demands for resource conservation, environmental protection and low emissions in the process of sustainable development, this study combines MXene with alkaline-treated hollow kapok fiber and integrates it onto a polyacrylonitrile (PAN) nanofiber mesh through vacuum filtration, successfully preparing a lightweight GO/MXene@NaOH-treated kapok fiber/PAN (GMKNP) composite material. Utilizing the natural hollow structure of kapok fibers and the gaps of the PAN nanofiber mesh as reflection units and thermal insulation units, while using the PAN nanofiber network as the mechanical support framework, through interfacial self-assembly, a multi-level pore structure is formed to achieve the synergistic integration of absorption-based electromagnetic shielding and low-frequency broadband sound absorption in a single biomass-based composite material. This layered porous structure enables the GMKNP to maintain a density of only 0.187 g/cm3, featuring an absorption-dominated shielding mechanism, where the absorption loss accounts for 78.4% of the total shielding effect, thereby effectively reducing secondary electromagnetic reflection. Its electromagnetic interference (EMI) shielding efficiency reaches 31.9 dB, effectively blocking electromagnetic radiation. The thermal conductivity of the material is only 0.09 W/(m·K), demonstrating excellent thermal management performance. Additionally, it shows a maximum sound absorption coefficient of 0.7 in the low-frequency range of 400-1600 Hz. This study provides a new multifunctional composite material design scheme with comprehensive sound, heat and electromagnetic protection capabilities for fields such as automotive cabins, aircraft interiors and green buildings.