Assembly of Polyimide/ <scp> Fe ₃ O ₄ </scp> ‐ <scp>MXene</scp> nanocomposite films with sandwich structure for electromagnetic interference shielding

Abstract The proliferation of electronic communication technologies has intensified challenges associated with electromagnetic interference (EMI), necessitating the advancement of flexible shielding materials that combine high performance with low reflectivity. Here, a high‐performance flexible PI/Fe 3 O 4 ‐MXene nanocomposite film with a sandwich structure was successfully prepared using a layer‐by‐layer assembly strategy. The modulation of the multilayer structure effectively realizes the functionalized integration of MXene, Fe 3 O 4 , and polyimide (PI), establishing a cascaded “absorption‐reflection‐reabsorption” mechanism for electromagnetic wave shielding. The nanocomposite films reveal excellent EMI shielding performance (57.0 dB) and increased absorption efficiency. Notably, the film maintains performance integrity across extreme operational conditions including cryogenic (−196°C) to elevated thermal environments (300°C), acidic exposure (pH = 2), mechanical stress (1000 bending cycles), and ultrasonic treatment, attributed to PI's inherent stability and interfacial stress dissipation within the multilayered system. In addition, the film exhibits outstanding mechanical properties (26.7 MPa tensile strength at 21.7% strain), exceptional thermal stability, and excellent thermal insulation performance (0.083 W (m K) −1 ). The high‐performance flexible EMI shielding composite film holds great potential for practical applications, particularly in the fields of electronic devices and communication technologies. Highlights The films with sandwich structure were prepared by a layer‐by‐layer assembly strategy. The films maintain stable EMI shielding performance under a variety of extreme conditions. The films have excellent thermal stability and insulation properties.