Revealing the dehydration/deuteration processes at the liquid-solid interface by nuclear magnetic resonance spectroscopy

The liquid-solid interface is of great importance in fundamental and applied research. However, the in-situ characterization of liquid-solid interfaces is very challenging. In this work, we demonstrated that {1H-29Si-}1H multiple-contact cross polarization with indirect detection (MCPi) solid-state nuclear magnetic resonance (ssNMR) spectroscopy is an excellent tool for studying dehydration and deuterium exchange at the solvent-silica interface. The results provided direct evidence that the physically adsorbed water molecules present on the silica surface were completely removed in the presence of DMSO, while the silanol groups were satisfactorily deuterated in the presence of a DMSO-D2O mixture. The knowledge obtained from the {1H-29Si-}1H MCPi experiment was also extended to the development of an 1H liquid-state NMR-based technique for the quantification of moisture and hydroxyls on inorganic and organic solids, as an alternative to the conventional thermogravimetric analysis (TGA) but with broader applicability. Moreover, this study offers a promising tool for studying the challenging questions involving liquid-solid interface.

Automated summary

This study demonstrates the use of solid-state nuclear magnetic resonance spectroscopy for studying dehydration and deuterium exchange at the liquid-solid interface. The results provide evidence of complete removal of physically adsorbed water molecules on the silica surface in the presence of DMSO, and satisfactory deuteration of silanol groups in the presence of a DMSO-D2O mixture. Additionally, the study develops a liquid-state NMR-based technique for quantifying moisture and hydroxyls on solids.