Hydroxyl environments in zeolites probed by deuterium solid-state MAS NMR combined with IR spectroscopy

Abstract

Deuterium (²H) solid-state MAS NMR spectroscopy is used for identifying both silanols and Brønsted acid sites in zeolites. The environments of hydroxyl groups in faujasite-type zeolites (FAU) with different aluminium contents and porosities in both acid- and sodium-forms were investigated. The results revealed a clear spectroscopic difference between zeolites possessing either silanols or both silanols and Brønsted acid sites compared to classical static ²H NMR spectroscopic studies. This study reinforces the versatility of solid-state MAS NMR spectroscopy and its synergy with IR spectroscopy to provide critical information on zeolite properties, adding a new tool to the set of characterizations available for silanols and Brønsted acid sites.