Interfacial water in mesopores and its implications to the surface features – A solid state NMR study

The temperature dependent morphologies of co-existing solid ice and interfacial water within two classic mesoporous materials, MCM-41 and SBA-15, are investigated below the Gibbs-Thomson transition temperature using Cryo-NMR, NMR spin-diffusion and NMR spectral analysis (second moment calculations). By using the combined NMR approach, the difference of the ice cores and interfacial water layers in MCM-41 and SBA-15 is unveiled. Based on the derived thickness of the interfacial water layers, the surface features in the two porous materials are discussed. The work demonstrates an approach to use the combined NMR techniques to study the porous material surface via probing the interfacial water layers, which can be used to study the physical/chemical properties of the material surface on the molecular level in general.