Sunlight-Sensitizing Switchable Photochromic Transparent Aesthetic Wood for Smart Windows

Photochromic transparent wood (PTW) is a kind of highly desirable, green, energy-saving building material with a practical aesthetic. The application of PTW in smart windows still faces daunting challenges owing to the poor stability of photochromic reversibility and low sensitivity to sunlight. In this work, we develop a kind of prominent switchable PTW based on poplar wood (SPTW-P) that shows high sensitivity to sunlight using a new simple fabrication method. In contrast to commonly reported UV-responsive counterpart, our SPTW-P, obtained by microencapsulating active component and polymer with matched refractive index, exhibits the fastest switchable (∼1.5 s) photochromic response to sunlight, high sensitivity of color changing from colorless to peachy pink, strong mechanical strength (87.3 MPa), good transparency, and ideal cycling stability, as evidenced by the 100% maintenance of its original photochromic effect after cycling 30 times. The SPTW-P material not only shows superb UV-blocking (the highest UV-blocking value is up to 97.7%) for protecting skin, excellent thermal insulation for energy saving, good size maintenance, wonderful shape, and chemical stability (100%), but also exhibits excellent aesthetic properties (e.g., moldable aesthetic patterns). This work could promote the development of aesthetic functional transparent wood as sustainable building materials to substantially reduce carbon emissions and energy consumption.