Structures And Properties Of Highly Symmetric Titanium-Oxo Clusters

Effectively harvesting solar energy plays a vitally important role in renewable-energy supply and environmental protection.Titanium dioxide(TiO2)nanoparticles are considered to have the most potential as photocatalysts for hydrogen production due to their low cost,high efficiency and environment-friendly characteristics.However,such nanoparticles show strong imprecise characteristics,including uneven sizes,unclear inorganic-organic interface information,and uncertain surface composition.These uncertainties have greatly hindered fundamental research on such important photocatalytic materials,such as catalytic mechanism,charge transfer,and surface modification.Therefore,acting as the structure and reactivity model complexes of TiO2nanoparticles,crystalline titanium-oxo clusters(TOCs)have attracted increasing research interest in recent years.Accurate atomic position,clear ligand-nuclearity connectivity,adjustable cluster size,and high solubility of TOCs have given great chances to the theoretical studies on photocatalytic properties.So far,although many TOCs with various structures have been reported,there are still many shortcomings such as low-nuclearity,low symmetry and poor stability.This research is devoted to prepare novel TOCs with high nuclearity,especially high symmetry,to synthesize TOCs with high stability by surface functionalization and to study the assembly of ?Ti3(?-O)3} units towards regularized supramolecular structures.The major achievements in this thesis are listed as follows:In chapter 2,under low-temperature solvothermal conditions with different temperatures,solvents,pH and time of reaction,first fullerene-like polyoxotitanium cage Ti42 and two high nuclearity Ti44 were prepared successfully through controlling the hydrolysis process of isopropyl titanium.They show high solution stability and good photocatalytic activity,respectively.The results not only enrich the member of fullerene family,but also indicate that high-nulearity TOCs have potential application in improving the photocatalytic activity of the materials.In chapter 3,by changing the amount of cyclohex-3-ene-l-carboxylate,four TOCs with good H2 evolution ability and high stability were synthesized.The results demonstrate surface functionalization of TOCs has potential application in both theory and photocatalytic water splitting.In chapter 4,through adjusting the configuration of dicarboxylic ligands,a series of TOCs based on ?Ti3(?-O)3} unit were obtained,including linear ?Ti3}2,triangle{Ti3}3.square {Ti3}4.The results show the stereo structure of ligands have a significant effect on the supramolecular assembly of TOCs units.