Multinuclear solid-state NMR studies of acidic and non-acidic hydroxyl protons in zeolites.

Among the variety of experimental techniques used for the characterization of aluminosilicate and aluminophosphate-based molecular sieves, NMR spectroscopy has the advantage of providing detailed information on local bonding and solid-state interactions. In the last 15 years, NMR has been used to study zeolitic frameworks, catalytic active centres, adsorbed probe molecules and their chemical interactions. This paper reviews multinuclear solid-state NMR studies of Brønsted acid sites in zeolites. The main topics are the formation, accessibility and localization of hydroxyl protons, dehydroxylation of zeolites, the interaction of hydroxyl protons with probe molecules, and the geometry and parameters of the local structure of OH groups in these materials.