Abstract: The full arrival of 5 G and advances in electronic integration make efficient heat dissipation crucial for stable operation and longer product lifespan. In this study, a vacuum-assisted filtration process was employed to fabricate ammoniated alumina/MXene/bacterial cellulose (Al₂O₃-NH₂/MXene/BC) composite films that display a unique integration of properties, encompassing ultra-high thermal conductivity (λ), mechanical flexibility, and high photothermal conversion performance. By leveraging the bridging effect among spherical Al₂O₃-NH₂ and MXene nanosheets, a densely packed “point-surface” structure was constructed in BC by using a one-step preparation process. When the mass fraction of Al₂O₃-NH₂/MXene (1:3, w/w) is 40 wt%, the O-BAl₁M₃ exhibited an in-plane λ of 20.02 W m^-1 K^-1, which was 436 % and 94 % higher than that of pure BC and T-BAl₁M₃ (prepared by a two-step method), respectively. Furthermore, constructing an intact thermal conductive network within BC notably promoted photothermal and photoelectric conversion performance. The maximum surface temperature and voltage of the O-BAl₁M₃ film reached 106.9 °C and 48.34 mV when a sample with an area of 1.56 cm² was exposed under a light intensity of 200 mW cm^-2. By applying O-BAl₁M₃ film, the temperature inside a self-built greenhouse model reached up to 64.8 °C within 1200 s under a light intensity of 100 mW cm^-2, which validated the practical application of the composite films and offered a novel approach for creating flexible films with superior photothermal conversion capability. This work provided insights into preparing functional composite films for efficient thermal management and photothermal conversion applications.

Key words: MXene, Bacterial cellulose, Composite film, Thermal conductivity, Photothermal conversion