Next-generation photochromic smart window: Wood-derived cellulose flexible composites integrated thermal insulation, UV-shielding, and anti-counterfeiting

Addressing the dual challenges of global energy sustainability and dynamic optical management, we present an innovative flexible photochromic transparent fluorescent wood composite film (PT-FWF) with molecular-scale engineered design, fabricated through in situ Eu³⁺ coordination on TEMPO-oxidized cellulose scaffolds. This hierarchically structured material combines fluorescent wood film with hot-pressing, impregnation, and coating (PMMA/WO₃) to achieve multimodal optical control. PT-FWF demonstrates exceptional multifunctionality: 88% optical transparency, 107.5° ± 1.0° hydrophobicity surface, and thermal insulation (ΔT ≈ 5.5°C). A unique dual-mode photoresponsive mechanism enables through synergistic photochromic-fluorescent effects: instantaneous fluorescence under UV light and coloring/bleaching with or without light-assisted (UV or simulated sunlight). The smart window model exhibits over 90% UV-blocking efficiency, and the transmittance of the smart window can be reversibly switched between 88% and 5% under prolonged light conditions, showing a high modulation of visible light (∆T_lum = 83%) at 1030 nm, enabling simultaneous daylight optimization and energy conservation. This molecular-scale engineered wood composite defines a transformative platform for adaptive optical materials, merging energy-efficient architectural solutions with information encryption through sunlight-regulated smart windows that simultaneously enable environmental protection and anti-counterfeiting. (Figure presented.).