Study of Conformation and Dynamics of Molecules Adsorbed in Zeolites by ¹H NMR

Abstract

The chapter “Study of Conformation and Dynamics of Molecules Adsorbed in Zeolites by ¹H NMR” is concerned with the application of high-resolution (HR) solid-state NMR techniques to study the behavior of molecules adsorbed on surfaces of nanoporous solids, such as zeolitic molecular sieves. This includes a combined or alternative application of conventional high-resolution NMR methods and of high-resolution solid-state NMR techniques, including magic-angle sample spinning (MAS), cross-polarization (CP), high-power decoupling and appropriate multiple-pulse sequences for two- or higher dimensional NMR and multiple-quantum spectroscopy. The interaction of adsorbed molecules with adsorption centers in the internal surfaces of porous solids does not only lead to changes in the reorientational and translational mobility of the molecular species but influences also the molecular conformation. Examples will be given for simple olefins in interaction with inner zeolite surfaces. Conclusions about the correlation times of the internal reorientational and translational dynamics are derived in complete agreement with the conclusion obtained from diffusion coefficients by means of PFG NMR (second chapter). Since the methodical approach of HR MAS NMR in heterogeneous systems presented here is also valuable for the investigation of lyotropic crystalline phases using HR MAS NMR (in Chap. 12) And for the NMR studies of cartilage (in Chap. 13) it was also the aim of this chapter to elucidate also the methodical background of these measurements in some more detail.