| Summary: | Bacterial cellulose (BC) has been recognized as an ideal supporter owning to its abundant hydroxyl groups on the surface. In this work, Keggin-type phosphotungstic acid (H3PW12O40, PWA) is self-anchored on the three-dimensional network of BC by a simple diffusion method at room-temperature. BC fibers can protect the well-dispersed PWA with high transparency, high mechanical strength, and high stability. When PWA/BC serves as a photochromic material, the coloration time and bleaching time are only 3 min and 30 min respectively. After 6 cycles, the photochromic ability of the PWA/BC composite film almost unchanged. At the same time, we convert the coloration and bleaching degree into quantitative data including a color difference calculation of ΔE2000 and the remaining degree of color (RC%). Within the BC system, PWA exhibits a special linear relationship between RC% and bleaching time (0–30 min). The processes of PWA/BC reduction (W6+→W5+) and oxidation (W5+→W6+) are analysed by photo-electrochromic, XPS and ESR characterizations. The revealed excellent photochromic properties of soft PWA/BC films highlight their potential as the photoresponsive materials.
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