The Preparation Of Mesoporous Molecular Sieves And Assembling ZnO Nanoclusters

The recent discovery of novel silica-based mesoporous materials designated as M41Shas opened up a new class of porous materials. As new functional materials, it exhibits orderedarrangement of pores with uniform pore size distribution and huge pore volume. Such uniquecharacteristics together with their extraordinary high surface area have many potentialapplications in separation, catalysis, biochemistry, nanostructured material and so on. Greatinterest has been focused on the synthesis, characterization and application of M41S.Supercritical fluid technology developed rapidly in recent years, it was used in manyresearch field. Supercritical fluid has unique property of physics and chemistry, such as, thelow viscosity and high diffusivity, which make it suited for rapid transport of reagents in toand out of the channels of porous materials.sc-CO₂ with low critical temperature andappropriate critical pressure, low cost, innocuity and low reaction nature, so in many fields itwas used widely such as Bioligy medicine, purification, macromoleculesynthesis, materialspreparation.In this work, it mainly researched synthesis of mesoporous materials, modified the surfaceof mesoporous materials selectively, extracted template of materials by supercritical CO₂ andsynthesized semiconductor nanoclusters ZnO inside the channel of mesoporous materials:(1) synthesized mesopomus materials MCM-41, MCM-48 using cationic surfactantcetyltrimethyl-ammonium bromide(CTAB) as template, tetraethoxysiliane as silicon source byhydrothermal method in basic solution, explored its proper condition of synthesis.(2) External grafting of phenyltrimethoxy-silane(Ph-Si) groups, internal modificationwith ethylenediamine groups, it has a strong ability to complex many metal ions. So theN-[3-(trimethoxysilyl)-propylethylene]diamine(designated as ED) was used to absorb Zn²⁺ toform metal complex, and it resured the reaction was acted in the channel of mesoporousmaterials.(3) The removal of the template from mesopores had been successfully achieved withsupercritical CO₂ modified with CH₂Cl/CH₃OH mixture. The extracted template retained itsstructure and property, and could be reused for preparation of mesoporous materials. Comparedto high temperature calcinations, the proposed method can avoid structure shrinkage, retainhighly uniform pore structure. (4) ZnO clusters had been fabricated in mesoporous materials with two methods of hightemperature calcalcination and O₃ oxidization. The mesoporous materials through functionalmodified and supercritical CO₂ extraction were used to absorb Zn²⁺ to form organic-inorganichybrids. Using two methods to remove organic component, compared two method, O₃oxidation is a good method, it can avoid the high temperature ion transfer and carry out lowtemperature operation. This method could be used to prepare other metal oxide.