Krause, S.; Evans, J.D.; Bon, V.; Crespi, S.; Danowski, W.; Browne, W.R.; Ehrling, S.; Walenszus, F.; Wallacher, D.; Grimm, N.; Többens, D.M.; Weiss, M.S.; Kaskel, S.; Feringa, B.L.: Cooperative light-induced breathing of soft porous crystals via azobenzene buckling. Nature Communications 13 (2022), p. 1951/1-10
10.1038/s41467-022-29149-z
Open Access Version
Abstract:
Although light is a prominent stimulus for smart materials, the application of photoswitches as light-responsive triggers for phase transitions of porous materials remains poorly explored. Here we incorporate an azobenzene photoswitch in the backbone of a metal-organic framework producing light-induced structural contraction of the porous network in parallel to gas adsorption. Light-stimulation enables non-invasive spatiotemporal control over the mechanical properties of the framework, which ultimately leads to pore contraction and subsequent guest release via negative gas adsorption. The complex mechanism of light-gated breathing is established by a series of in situ diffraction and spectroscopic experiments, supported by quantum mechanical and molecular dynamic simulations. Unexpectedly, this study identifies a novel light-induced deformation mechanism of constrained azobenzene photoswitches relevant to the future design of light-responsive materials.