Solid-state NMR studies of zeolites

Abstract

Due to having unique pore structures and intrinsic acid-base properties, zeolites have been widely used in ion exchange, adsorption, and catalysis in chemical and petrochemical industry. Solid-state NMR is a well-established tool for the structural characterization of zeolites. The detailed information about the zeolite framework can be obtained from multinuclear and multidimensional 1 H, 29 Si, 27 Al, and 17 O MAS NMR spectroscopy. The structure and communication of cages and channels in zeolites can be extracted by 129 Xe NMR spectroscopy. The acidic properties of zeolites can be well characterized through solid-state NMR probe molecule techniques. In addition, two-dimensional (2D) 1 H- 1 H and 27 Al- 27 Al double- quantum (DQ) MAS NMR experiments are utilized to probe the spatial proximities and the synergy effect between different acid sites in zeolites. Moreover, in situ solid-state NMR is able to explore the mechanism of zeolite-catalyzed reactions by monitoring the evolution of the reactants, intermediates, and products. The crystallization mechanism for synthesis of zeolites can be elucidated by detecting the variation of framework 29 Si, 27 Al, and 31 P NMR signals at different crystallization stages.