Light-Induced Color Switching of Single Metal–Organic Framework Nanocrystals

Photoinduced modulation of the optical parameters of nanomaterials underlies the operating principles of all-optical nanodevices. Here, we demonstrate the laser-induced 10% modulation of the refractive index and 16-fold modulation of the extinction coefficient of the dynamic metal–organic framework (HKUST-1) nanocrystals within the whole visible range. Using the laser-induced water sorption/desorption process inside HKUST-1, we have achieved size-dependent reversible tuning of brightness and color of its nanocrystals over the different spatial directions and color palette. The numerical analysis also confirmed the detected optical tuning through the evolution of optical spectra and directivity of the scattered light. The results of the work demonstrate the promising nature of the dynamic metal–organic frameworks for nonlinear optics and expand the library of chemically synthesized hybrid materials with light-controlled optical properties.