Ligand Dynamics of Drug-Loaded Microporous Zirconium Terephthalates-Based Metal-Organic Frameworks: Impact of the Nature and Concentration of the Guest

Impact of encapsulation of model drug molecules bearing different chemical features (caffeine or ibuprofen) over the molecular dynamics of a series of functionalized zirconium terephthalate UiO-66(Zr) type metal-organic frameworks was investigated by dielectric relaxation spectroscopy. If the rotational motions of the ligands are more significantly perturbed by the guest dimension and loading rather than their chemical features, the dynamics strongly depends on the nature of the functional group of the terephthalate ligand, as shown typically when comparing the amino- or bromo-functionalized forms. While for UiO-66(Zr)-NH2 the dynamics of the ligands is partially enhanced in the presence of both drugs, the scenario differs for the bromo form which shows a slower dynamics. This is discussed from a qualitative analysis of the global interactions within these solids as a matter of the ligand/framework and ligand/guest molecules pairs of interactions.