서강대학교

초록/요약

New materials chemistry and especially new nanomaterials chemistry is essential to meet the need of increasing in energy demand and power density and also to meet the future challenges of energy storage for future generation. Order uniformly mesoporous crystalline TiO2 nanostructure and periodic mesoporous organosilicas (PMOs) consider to be a new material for fundamental advance in energy conversion and storage because of their unique electronic and optical properties. But the synthesis of order uniformly mesoporous crystalline material is still complicated because of difficult to controlling the crystallinity and porosity of the particle or cluster and phase transformation. We successfully overcome all barrier and going to report the first time order uniformly mesoporous crystalline TiO2B very large scale, steam assisted highly crystalline order uniformly mesoporous anatase and also microscopic structure analysis of three crystal like PMOs. Our synthesized catalyst shows superior photo catalytic H2 production from water and photocatalytic degradation of dye. TiO2-B is unique in the sense that it has crystalline voids which can readily intercalate small cations. Accordingly, coupled with the fact that Ti(IV) in TiO2 can be easily reduced to Ti(III), TiO2-B is currently receiving a great attention as a potential electrical energy storage material and as a photocatalyst. Its performance has been expected to increase significantly if it can be prepared in the form of ordered uniformly mesoporous TiO2-B (oum-TiO2-B). We now report the first synthesis of hexagonally ordered uniformly mesoporous TiO2-B (h-oum-TiO2-B), especially in a large scale (> 10 g) in high purity. The band gap energy of h-oum-TiO2-B decreases with respect to that of nanoparticles by 0.36 eV. h-oum-TiO2-B shows much higher performances during the photocatalytic applications for hydrogen production from methanolic water, decomposition of 4-chlorophenol (4-CP) and methylene blue (MB). Anatase, the most important polymorph of TiO2, is one of the most important crystalline metal oxides which are currently widely used in industry and in academia for various purposes, in particular as photocatalysts. The applications of anatase benefit most when it exists in the uniformly mesoporous (UM) form, which has conventionally been prepared by heating the amorphous UM TiO2 precursor at temperatures between 550 and 800 ͦ C However, such high temperature methods are not desirable from the energy saving and scalability points of view. We report a steam-assisted low temperature (120 ͦ C, 1 h) large scale method to convert the corresponding hexagonally ordered amorphous precursor to highly crystalline hexagonally ordered UM (h-UM) anatase. Despite the fact that the wall thickness of h-UM anatase is only ~5 nm, the UV-vis absorption onset red-shifts to the visible region by more than 30 nm with respect to that of 25-nm sized anatase nanoparticles, owing to the extensive three-dimensional networking of the crystalline wall. Due to this phenomenon, h-UM anatase shows much higher photocatalytic activities during dye decomposition and water reduction under visible light PMOs is considered to be a new class of materials characterized by large specific surface areas and long range order uniform pore sizes between 2 and 15 nm, crystal like well order morphology have been obtained through the coupling of inorganic and organic components by template assisted. First time we reported the under basic condition same cationic surfactant containing charge balance halide anions play important role for the controlling of various well order crystal like morphology and channel orientation. In this thesis we are describing the systematic detail microscopic structural analysis of three crystals like well order morphology of PMOs. We believe this exceptional microscopic crystal structure analysis of periodic mesoporous organosilicas and their unique properties open up a new avenue in material chemist that might have a significant impact on crystal engineering, materials science, and various significant applications like photo catalysis and solar cells. The presence of various charge balance counter anions (halide) in the interfacial region of the precursors of organosilicas -surfactant mesophase which was self introduces opportunities for manipulation of the phase structure of PMOs and also channel direction. Our as synthesis novel periodic mesoporous organosilicas have high surface area, long range order of uniform mesoporosity, cylindrical pore geometry, densely pore volume and solid state13C and 29Si MAS NMR clearly illustrated carbon and silica were 100% covalently bonded.