Versatile flexible N-doped MXene based composite films via multidimensional heterostructure engineering for multiband...

MXenes, celebrated for their exceptional photothermal conversion, electrical and electromagnetic properties, are promising for integrated thermal-electromagnetic management. However, their cross-band synergy is hindered by high conductivity-induced strong microwave reflection and nanosheet restacking. Herein, we propose a triple-scale design strategy-microscopic defect engineering, multi-dimensional heterostructure assembly, and macroscopic gradient integration-to fabricate flexible 0D/1D/2D synergistic composite films. Nitrogen-doped MXene (N-MXene) introduces lattice defects to optimize dual properties; 0D amino-functionalized hollow mesoporous silica nanoparticles (NH₂-HMSNs) suppress restacking and boost dielectric loss, 1D bacterial cellulose enables flexibility, and the macroscopic gradient achieves gradual microwave impedance matching. This elaborate design enables coordinated thermal and electromagnetic performance across multiple spectral bands: under 0.5 Sun irradiation, the 65 µm-thick gradient film reaches a maximum surface temperature of 77.0 °C while exhibiting >89% absorption in the mid-to-long-wave infrared (MWIR-LWIR) range, demonstrating efficient solar-thermal conversion and MWIR-LWIR radiative management. For microwave absorption, the 1 mm-thick composite film achieves a reflection loss (RL_min) of -52.71 dB at 13.77 GHz, together with an EAB of 11.43 GHz covering the entire measured 6.57-18.00 GHz range. The film additionally exhibits superior mechanical robustness, self-extinguishing behavior, and photothermal cycling stability. This work delineates N-MXene's multi-band potential, provides a scalable platform for programmable thermo-EM management materials, and offers insights for infrared radiative management and microwave actuators.