Structural Design And Band Gap Engineering Of Titanium-oxo Clusters Based On Phenolphosphonate And Salicylate Ligands

Titanium dioxide(TiO2)nanoparticles play a crucial role as anodes in photovoltaic cells,and as photocatalysts in processes such as the oxidation of organic compounds in polluted air and wastewater,because of its good physical properties,minimal environmental impact and large abundance.However,most of the applications of TiO2 have been limited only in the UV light range(<5%of the solar spectrum)due to its large bandgap(?3.2 eV).Therefore,it is requisite to extend the optical response of TiO2 into visible light area.A great number of literatures based on the doping TiO2 with metal ions or non-metallic p-block elements have been reported.As the structure and reactivity model compounds of bulk nanoscale TiO2,titanium-oxo clusters(TOCs)are usually crystalline materials and can provide precise structural information by X-ray diffraction studies.Therefore,the research on functional TOCs has attracted increasing attention in recent years.Metal ions doping and chromophore ligands functionalization have also been applied to tune the adsorption behaviors and electron transporting of TOCs.However,the systemic studies on their struture design and bandgap engineering are still very rare.In this thesis,through low-temperature solvothermal synthesis,we have successfully prepared a series of novel titanium-oxo clusters functionalized by phenolphosphonate/salicylate ligands,transition or lanthanide metal ions.The obtained TOCs represent good visible light adsorption and efficient photocatalytic hydrogen evolution activities.These results not only make important improvements on the structure design and bandgap engineering of TOCs,also provide useful models for better understanding the structure-property relationships of TiO2.In chapter 2,under solvothermal conditions,through the labile coordination sites of a robust phosphonate-stabilized titanium-oxo cluster,8 O-donor ligands have been successfully introduced without changing the cluster core.Transition-metal ions are then incorporated by the use of bifunctional O/N donor ligands,organizing these {Ti6}clusters into polymeric structures.The coordination environments of the applied metal ions show significant influence on their visible-light adsorption.Both the above structural functionalizations also tune the photocatalytic H2 production activities of these clusters.In chapter 3,salicylic acid with versatile binding modes has been selected as bridging ligands.Two interesting titanium-oxo molecular squares are constructed in the presence of aromatic dicarboxylate,which display good optical and photocatalytic properties.Then transition and lanthanide metal ions are successfully doped to give three novel heterometallic TOCs with low bandgaps.