| Summary: | <p>This thesis discusses the development of novel titanium-containing layered double hydroxides (Ti-LDHs) as semiconductor photocatalysts for the photo-oxidation of simple organic molecules. LDHs are introduced in Chapter 1 as compositionally flexible anionic clays, whose layered structure and tuneable properties make them highly interesting in a wide range of applications, including environmental purification, drug delivery and photocatalysis. In the latter case, LDHs have been used primarily in the photocatalytic degradation of organic pollutants, photo-reduction of CO<sub>2</sub> and photocatalytic water splitting. Only limited research has been done into the controlled organic molecule photo-oxidation, where the oxidation is stopped at an intermediate stage rather than proceeding all the way to degradation products.</p>
<p>Chapter 2 outlines the five different synthetic methods for Ti-LDH preparation and their viability in the synthesis of pure NiTi- and MgAlTi-LDHs with different Ni:Ti and Al:Ti ratios, respectively. The crystallinity, morphology, structure, composition and band gap energies of the Ti-LDHs were analysed, so as to determine the effect of the synthetic conditions and Ti content on their properties. Furthermore, the highly crystalline urea hydrothermal MgAlTi-LDH samples were characterised by high-angle annular dark-field imaging (HAADF) as well as by <sup>1</sup>H, <sup>27</sup>Al and <sup>47/49</sup>Ti solid state NMR spectroscopy.</p>
<p>In Chapter 3, the activity of the Ti-LDHs in the photo-oxidation of diphenylmethanol is studied, and compared to that of anatase TiO<sub>2</sub> as a benchmark photocatalyst. The importance of short-wavelength radiation is discussed, especially for control experiments in the absence of a catalyst. The effects of the synthetic method, Ti content, catalyst and reactant loading, and irradiation time were examined for selected Ti-LDHs.</p>
<p>Chapter 4 extends the study of the photocatalytic properties of Ti-LDHs beyond diphenylmethanol photo-oxidation to also include benzyl alcohol, cyclooctanol and benzylamine. This allows the determination of whether Ti-LDHs can be used to photo-oxidise a wider range of functional groups as part of either aromatic or aliphatic systems.</p>
<p>Lastly, Chapter 5 details the synthesis and characterisation of TiO<sub>2</sub>@Ti-LDH core-shell hybrid materials, and looks at their application in the photo-oxidation of diphenylmethanol. The conversion using the core-shell photocatalysts was compared to that obtained with a mechanical mixture of TiO<sub>2</sub> and Ti-LDHs, in order to study any synergistic heterojunction effects.</p>
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