Supercritical CO ₂ ‐Induced Porous MXene Films for Electromagnetic Interference Shielding and Infrared Stealth

ABSTRACT Lightweight and flexible porous MXene films have emerged as promising candidates for electromagnetic interference (EMI) shielding and infrared stealth. However, current foaming techniques remain a challenge in preserving the intrinsic properties of MXene while achieving eco‐friendly foaming. Herein, supercritical CO ₂ foaming technology is employed to realize the green foaming of dense MXene films without compromising the inherent structure of the MXene nanosheets. The phase transition of supercritical CO ₂ induces bubble nucleation and growth, effectively unfolding the stacked MXene nanosheets into a porous architecture. This strategy is broadly adaptable and can also be extended to other two‐dimensional (2D) films, such as graphene oxide. Benefiting from highly‐conductive porous skeleton, the foamed porous MXene film exhibits an EMI shielding effectiveness of ∼73.2 dB, which is 21% higher than that of the pristine MXene films. Furthermore, its absolute shielding effectiveness attains 23160 dB·cm ² /g, surpassing most previously reported MXene‐based porous materials. Notably, the porous MXene films also demonstrate excellent infrared thermal camouflage performance across a broad temperature window. This work not only offers an insight for the foaming of 2D MXene materials but also highlights the considerable engineering prospects of porous MXene films in the field of safety protection.