Resilient photoswitchable metal–organic frameworks for sunlight-induced on-demand photochromism in the solid state

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2023-11, Vol.476, p.146727, Article 146727
• Main Authors: Mollick, Samraj, Zhang, Yang, Kamal, Waqas, Tricarico, Michele, Möslein, Annika F., Kachwal, Vishal, Amin, Nader, Castrejón-Pita, Alfonso A., Morris, Stephen M., Tan, Jin-Chong
• Format: Article
• Language: English
• Subjects: Mechanical property; Metal-organic frameworks (MOFs); Nanocomposites; Photostable; Solid state photochromism
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2023.146727

[Display omitted] •Mechanically robust and optically resilient photochromic films achieved via MOF encapsulation.•Generic design rules for solid-state photochromic composites with fast switching are elucidated.•Photoswitchable applications include smart windows, ink-jet printed coatings, and self-erasing surfaces. Organic photoswitchable molecules have struggled in solid-state form to fulfill their remarkable potential, in terms of photoswitching performance and long-term stability when compared to their inorganic counterparts. We report the concept of non-electron deficient host’s surface with optimal porosity and hydrophobicity, as a priori strategy to design photoefficient organic solid-state photochromic materials with outstanding mechanical robustness. It is realized by the nanoconfinement of photochromes in a host matrix possessing optimal porosity and hydrophobicity. The resulting photochromic nanocomposites can be prepared in multigram scale employing a one-pot reaction under ambient conditions. When exposed to a light stimulus including natural sunlight, the photoswitchable nanocomposite powder changes color promptly and reversibly, in a matter of seconds (5 s and 30 s under UV irradiation and sunlight, respectively) along with excellent photo-fatigue resistance, which are on a par with inorganic photochromes. Exemplars of commercially viable prototypes that are optically clear, comprising smart windows, complex photochromic sculptures, and self-erasing rewritable devices, were engineered by direct blending with resilient polymers. Notably, the use of high-stiffness polymers (Young’s modulus > 2 GPa) is no longer considered an insurmountable challenge. Finally, photochromic films with anticounterfeiting features could be manufactured through precision printing of nanocrystals by drop-on-demand inkjet printing technology.