Ultra-high field solid-state NMR of microporous materials at 1 GHz and beyond: A mini review

Microporous materials, including zeolites and metal-organic frameworks (MOFs), play pivotal roles in a wide range of applications such as catalysis, gas adsorption/separation, drug delivery, and chemical sensing. Establishing their structure-property relationships requires detailed characterization of local structures. Solid-state nuclear magnetic resonance (NMR) spectroscopy, as an isotope- and site-specific technique, is ideally suited for probing local chemical environments at atomic level in these materials. However, many NMR-active nuclei in microporous materials are inherently unreceptive due to low gyromagnetic ratios, low natural abundances, and/or large quadrupolar interactions. The advent of ultra-high magnetic fields at 1 GHz and beyond has significantly expanded the capabilities of solid-state NMR by offering substantial gains in both sensitivity and resolution. This review summarizes recent advances in solid-state NMR studies of microporous materials enabled by ultra-high magnetic fields. We first briefly introduce the sensitivity enhancements afforded by high-field NMR and the development of ultra-high field magnet technologies. We then discuss the experimental methodologies for characterizing microporous materials at ultra-high magnetic fields. We highlight the recent multinuclear solid-state NMR studies that elucidate metal centers, organic linkers, and host-guest interactions in zeolites and MOFs at ultra-high magnetic fields. Finally, we discuss emerging opportunities and future research directions for ultra-high field solid-state NMR in the study of microporous materials.