Two Approaches to Solid-State NMR of Mobile Molecules in Nanoporous Materials

This paper reviews two solid-state NMR approaches for investigating mobile molecules in nanoporous materials, with a focus on the motion-averaged dipole-dipole interactions of nuclear spins. The first approach addresses intramolecular dipole-dipole interactions, where the anisotropic molecular motion in solids leads to partially averaged interactions that reflect the spatial distribution of molecular positions during motion. The second approach examines intermolecular dipole-dipole interactions, which produce anisotropic features in NMR spectra and affect nuclear spin relaxation due to the Brownian motion of molecules within non-spherical nanoscale pores. The applicability of these methods is considered for systems exhibiting molecular mobility, including zeolites, collagen tissues, intercalation compounds, and plant stems.