Ultrasound-Assisted Facile Nanoconfinement of Luminescent Guests in Zirconium Metal-Organic Frameworks

An accelerated sonochemical route for fabricating luminescent guest-MOF (LG@MOF) composites is demonstrated, for which light-emitting molecules are nanoconfined within porous zirconium-based hosts using probe ultrasonication rather than conventional bath sonication. Ultrasonication enables the rapid synthesis of crystalline UiO-66 and UiO-67 nanocrystals within 10 minutes, with material yields of up to 92%, and facile in situ guest encapsulation within 1 hour, hence notably faster than the traditional 24-hour solvothermal route. Using UiO-66 and the larger-pore UiO-67 as porous hosts, tuneable single- and dual-guest fluorescent host-guest systems incorporating Rhodamine B (RB) and Fluorescein (F) were achieved. Photophysical characterisation showed broadband emission, tuneable colours, high quantum yield and improved lifetime, highlighting the synergy between sonochemical conditions, structural defects, and photophysical behaviour. Additionally, the sonochemically prepared LG@UiO particles show well-defined crystal facets and potential as photoactive thin films for solid-state lighting, demonstrating their promise as a tuneable light source for optical sensing and nanophotonics.