An Electric‐Magnetic Dual‐Gradient Composite Film Comprising MXene, Hollow Fe 3 O 4 , and Bacterial Cellulose for High‐Performance EMI Shielding and Infrared Camouflage

Abstract It is crucial to develop electromagnetic interference (EMI) shielding materials with high shielding efficiency (SE) and reduced reflection to mitigate the secondary pollution caused by electromagnetic waves (EMWs). Herein, a novel multilayer assembly strategy inspired by the structure of “Turkish dessert—Baklava” is proposed to introduce magnetic hollow Fe 3 O 4 nanospheres (HFO) and conductive MXene nanosheets into a bacterial cellulose (BC) network. Through a layer‐by‐layer vacuum filtration approach, a composite BC/MXene/HFO film with a controllable electric‐magnetic dual‐gradient structure is achieved. The construction of electric‐magnetic dual gradients alleviates the impedance mismatch at the air‐film interface, resulting in reduced reflectivity toward EMWs, while the unique hollow structure of HFO facilitates the “absorption–reflection–reabsorption” process of EMWs. Consequently, the as‐prepared composite film (0.35 mm thickness) exhibits an extraordinary EMI SE of 67.6 dB and a reflection SE as low as 5.1 dB. Furthermore, it also demonstrates exceptional mechanical properties, efficient thermal management, and Joule heating capabilities, as well as remarkable passive and active infrared camouflage performances. This study offers an innovative approach to achieve less reflection and more absorption of EMWs, and expands the application scope of EMI shielding materials in precision electronics, aerospace, and military equipment fields.