Ultrafine cellulose nanocrystal-reinforced MXene biomimetic composites for multifunctional electromagnetic interference shielding

Polymers are widely employed to improve the mechanical properties of transition metal carbides and/or nitrides (MXenes) for constructing high-performance electromagnetic interference (EMI) shields. The challenges involve the insulating-polymer-induced compromise of electrical conductivity and EMI shielding performance of the MXene-based composites and the employment of nonrenewable, petrochemical polymers. Here, the one-dimensional, ultrafine, sustainable cellulose nanocrystals (CNCs) are efficiently employed to reinforce the MXene nanosheets, giving rise to high-strength, highly flexible biomimetic composites that maintain excellent electrical conductivity and EMI shielding effectiveness (SE). The freestanding MXene/CNC nanocomposites gain EMI SE values of 30 to 66 dB at thicknesses of approximately 2 to 14 µm, leading to ultrahigh specific SE and surface-specific SE values of 15,155 dB mm −1 and 54,125 dB cm 2 g −1 , respectively, which are comparable to those of the best EMI shields ever reported. Moreover, the excellent photothermal performance of the composite films was achieved, extending the application scenarios. Combined with the universal, facile, energy-efficient, and scalable ambient pressure drying preparation approach, the ultrathin, flexible, high-strength, and multifunctional CNC-reinforced MXene-based biomimetic films have shown great potential for applications in next-generation advanced flexible electronic or aerospace systems.