Multi-nuclear NMR spectroscopy can provide significant insight into the behavior of ions and fluid species on solid surfaces and in the interlayer galleries of layer structure materials. Such materials are typically statically and dynamically disordered, limiting the effectiveness of diffraction methods and making spectroscopic methods the tools of choice for exploring structure and dynamics of these species. The development of high-pressure tools compatible with the resolution enhancements of magic angle spinning have increased the types of questions we can ask and address about molecular adsorption and dynamics at such solid-fluid interfaces using NMR. However, it is often difficult to unambiguously interpret the NMR results in terms of structural and dynamical behavior, especially since investigating such fluid behavior typically involves NMR experiments at multiple temperatures, fluid water contents, and the range of possible variants in solid phase composition. Because the interaction of fluid species with each other and with the solid phase is often dominated by Coulombic and H-bond interactions, computational molecular modeling (often using molecular dynamics [MD] methods) can be of great assistance in interpreting the experimental results. This talk will discuss two examples of the synergy between NMR and molecular modeling to provide otherwise unobtainable insight into the structure and dynamic behavior of fluid species and ions at solid surfaces and in interlayer galleries. Examples will include results for expandable clay minerals (smectites) in contact with aqueous and non-aqueous fluids, including recent MAS NMR studies of cations, H2O, CO2, and CH4 at elevated pressures and temperatures.

Linking NMR spectroscopy and computational molecular modeling to understand layer structure material

ACS Spring Meeting 2021

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