Modulation of porosity in a solid material enabled by bulk photoisomerization of an overcrowded alkene.

The incorporation of photoswitchable molecules into solid-state materials holds promise for the fabrication of responsive materials, the properties of which can be controlled on-demand. However, the possible applications of these materials are limited due to the restrictions imposed by the solid-state environment on the incorporated photoswitches, which render the photoisomerization inefficient. Here we present responsive porous switchable framework materials based on a bistable chiroptical overcrowded alkene incorporated in the backbone of a rigid aromatic framework. As a consequence of the high intrinsic porosity, the resulting framework readily responds to a light stimulus, as demonstrated by solid-state Raman and reflectance spectroscopies. Solid-state 13C NMR spectroscopy highlights an efficient and quantitative bulk photoisomerization of the incorporated light-responsive overcrowded olefins in the solid material. Taking advantage of the quantitative photoisomerization, the porosity of the framework and the consequent gas adsorption can be reversibly modulated in response to light and heat.