Robust multifunctional MXene-based composite films with Janus-like structure for high-performance electromagnetic interference shielding, electrothermal conversion and infrared stealth

MXene holds promising potential for electromagnetic interference (EMI) shielding applications; however, pure MXene films suffer from poor mechanical properties and pronounced impedance mismatch both of which limit their practical application and lead to electromagnetic radiation secondary pollution. Currently, the mechanical properties are commonly improved by directly incorporating polymers into MXene, but this compromises EMI shielding performance. Herein, inspired by Janus-like structure, we report a novel asymmetric and multifunctional composite film comprised of blended Fe₃O₄ nanoparticles, carbon nanotubes (CNT), and cellulose nanofibers (CNF) as the top ‘impedance matching’ layer, CNF as the middle ‘mechanical’ layer and MXene as the bottom ‘reflection’ layer by sequential vacuum-assisted filtration. The film delivers an excellent tensile strength of 119 MPa, originating from the strong CNF middle layer and the efficient hydrogen bonding with the top and bottom functional layers. Notably, profiting from rational modulation of component proportions and the unique Janus-like architecture, the film with a MXene content of 30 wt% shows an impressive EMI shielding effectiveness (EMI SE) of 49.1 dB with an improved microwave absorption (SE_A) of 39 dB and an exceptional absolute shielding effectiveness (SEE/t) of 9487 dB·cm²·g⁻¹, attributed to the absorption-reflection-reabsorption process. The EMI SE is boosted to 75.58 dB by simply stacking 3 pieces together, achieving a high shielding efficiency that approaches nearly 100 %. Moreover, such film exhibits excellent electrothermal conversion and infrared stealth performance. This work presents a promising strategy to develop flexible and robust MXene-based composite films for advanced EMI shielding applications in wearable electronics and military equipment.