  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.
