Surface modulation of metal-organic frameworks for on-demand photochromism in the solid state

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. When exposed to a light stimulus including natural sunlight, the photoswitchable nanocomposite changes color promptly and reversibly, in a matter of seconds 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; particularly, the use of high-stiffness polymer (> 2 GPa) is no longer an insurmountable challenge. Finally, photochromic films with anticounterfeiting features could be manufactured through precision inkjet printing of nanocrystals.