Exploring zeolite water interactions using a combined experimental-theoretical NMR approach

Abstract

The aim of the work in this thesis is to use a combined experimental and theoretical approach to investigate the behaviour of water in zeolites. Recently, zeolite-water interactions have gained interest in the literature, as aluminosilicate zeolites show facile lability in water. This phenomenon affects how we view zeolites, however this mechanism is not fully understood. Experimental 17 O NMR has allowed for the observation of zeolite-water interactions and ab initio molecular dynamics studies have highlighted the surprising and complex behaviour of water in zeolites. A combined experimental-theoretical approach enables a better understanding of zeolite-water interactions, but new theoretical methods must first be developed to model zeolite-water structures realistically and these methods must be applied to simpler zeolite models such as siliceous zeolites. This is what was performed over the course of this PhD project. This thesis has shown that experimental 17 O NMR indicates clear 17 O-enrichment of selected siliceous zeolites (AFI, FER and MFI) regardless of 17 O-enrichment method, implying that this lability is a general feature of high silica and siliceous zeolites. The extent of 17 O- enrichment of the framework oxygens varied due to the presence of silanols and differences in the zeolite...