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.