Gradient sandwich MXene/CNF/PVA/Fe3O4 polymer composite films with efficient electromagnetic interference shielding and photothermal performance

Flexible polymer composite films that integrate electromagnetic interference (EMI) shielding, mechanical robustness, and photothermal conversion are highly desirable for emerging wearable and portable electronic devices. Herein, gradient sandwich-structured MXene/CNF/PVA/Fe 3 O 4 polymer composite films were fabricated via a layer-by-layer vacuum-assisted filtration strategy, in which conductive MXene layers and magnetic Fe 3 O 4 layers were assembled with cellulose nanofibers (CNF) and poly(vinyl alcohol) (PVA) serving as flexible polymer matrices. Benefiting from the synergistic combination of conductive loss, magnetic loss, and interfacial polarization induced by the gradient sandwich architecture, the polymer composite films exhibit enhanced electromagnetic wave attenuation with improved impedance matching. The optimized composite film with an ultrathin thickness of 0.138 mm delivers a high EMI shielding effectiveness of approximately 52 dB in the X-band (8.2-12.4 GHz), with a significantly enhanced absorption contribution (∼40 dB). While, strong hydrogen-bonding interactions among MXene, CNF, and PVA effectively reinforce the polymer composite framework, resulting in a tensile strength of up to 14.8 MPa and a toughness of ∼177 MJ·m -3 . In addition, owing to the photothermal conversion capability of MXene, the composite film rapidly heats to 65.8 °C under simulated solar irradiation (1000 W·m -2 ). This work demonstrates an effective structural design strategy for multifunctional gradient sandwich polymer composite films, providing a feasible route toward lightweight, flexible, and high-performance EMI shielding materials for wearable and portable electronics. • Gradient sandwich MXene/CNF/PVA/Fe 3 O 4 composite films were constructed via layer-by-layer vacuum-assisted filtration. • Synergistic conductive-magnetic coupling and interfacial polarization enhance the absorption contribution in the overall EMI shielding. • An ultrathin film (0.138 mm) achieves ∼52 dB EMI SE in the X-band with ∼40 dB absorption. • Hydrogen-bonding-enabled interlayer cohesion yields 14.8 MPa strength and ∼177 MJ·m -3 toughness. • MXene-enabled photothermal conversion rapidly raises the surface temperature to 65.8 °C under simulated solar irradiation.