Novel aspects of layered double hydroxide chemistry

Thesis

A number of different aspects of the chemistry of layered double hydroxides and similar materials have been explored in this thesis. The intercalation chemistry of these compounds, in both aqueous and mixed solutions, has been explored to synthesise over forty new hybrid layered materials by ion-exchange and rehydration-reconstruction methods. The host used include both previously-reported layered hydroxide compounds, and novel host materials synthesised by the extension of heterogeneous reactions of solid oxides. The synthesis of these novel materials provides insights into the factors that control the compatibility of the metal ions that may form hydrotalcite-like structures, in addition to providing compounds that may act as the precursors of catalysts and other functional materials.

The new intercalation compounds synthesised show interlayer distances ranging from 7.1Å to 23.6Å, and demonstrate a variety of interlayer alignments as determined by powder X ray diffraction, dependent upon both the metallic content and the degree of hydration of the host compound. The anionic contents of the interlayer regions have been further characterised through infra-red spectroscopy, elemental microanalysis, solid-state NMR and thermogravimetric analysis techniques.

The mechanism and kinetics of the release of the intercalated anions from the hosts have been studied in situations approximating their real-world applications, and the degree of release quantified by UV/Visible spectroscopy. Both the rates and mechanisms of anion release have been found to be dependent on the anion, the host, the temperature and the solution into which the anions are released; as such, the release timescales of the anions may be fined tuned through modifications of the host materials. In addition, an explanation has been suggested for the observed change in mechanism observed in instances of release in which the host compound is in only partial contact with the release medium.

Authors: Markland, C

• Publication date: 2013
• DOI: 10.5287/ora-4rjeownd2
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: solid; synthesis; state; hydroxide; double; materials; layered
• Subjects: Solid state chemistry; Inorganic chemistry; Chemistry & allied sciences