Preparation Of Ordered Mesoporous Inorganic-Organic Functional Materials And Studies Of Their Catalytic Performances In Water-Medium Organic Reactions

As the world's growing concern on environmental protection, green chemistry has caused increasing attention. On one hand, organic reactions carried out in water medium has become a new trend of green chemistry since water is the most innocuous substance on Earth and therefore the safest solvent possible. On the other hand, the immobilization of homogeneous catalyst could simplify the isolation procedure for recycling the catalyst, further reducing synthesis costs and heavy metal pollution.However, the heterogeneous catalysts always induced aggregation and the enhanced diffusion limit as well as the change of chemical environment of the active sites, which will cause the decreased catalytic efficiencies in chemical reactions. Recently, immobilization of homogeneous catalysts on the mesoporous supports seems a promising way to develop highly active heterogeneous catalysts. The high surface area and ordered pore structure will promote the uniform dispersion of active sites and also diminish the steric hindrance for diffusion of reactant molecules. Furthermore, the innert solid support will accommodate the active sites to stabilize chemical environment, which will improve the stability of the heterogeneous catalysts.According to our early studies, the mesoporous silica materials modified with hydrophobic group could promote the adsorption and diffusion of organic reactants to active sites especially in water media, which enhanced the catalytic activity of heterogeneous catalysts. Furthermore, the heterogeneous catalyst prepared by post-grafted method always showed lower catalytic activity mainly due to the blockage of the mesopore. This thesis systemly studies the differences of catalytic efficiency between hydrophilic and hydrophobic supports such as periodic ordered silica and organosilica (PMO). In addition, the influence of immobilization methods such as co-condensation and post-grafting were also concerned.1, Ethyl-bridged periodic mesoporous organosilicas (PMO) functionalized with PPh2 ligand was synthesized, which was used as a support for post-grafting Pd(â…¡) organometallic catalyst by coordination reaction between P and Pd(â…¡). The as-prepared Pd(â…¡)-PPh2-PMO(Et) exhibited high activity in water-medium Barbier reaction and could be used repetitively. The high activity could be attributed to the high dispersion of Pd(â…¡) active sites and ordered mesopore channels which effectively diminished the steric hindrance and diffusion limit. Furthermore, the ethyl-fragments and the PPh2-ligands in the support wall could synergic enhance surface hydrophobicity, which promoted the adsorption for organic reactant molecules.2. A facile approach to prepare phenyl and Rh(â… ) organometal bridged periodic mesoporous organometalsilica was developed based on surfactant-directed co-condensation of RhCl[PPh2(CH2)2Si(OEt3)3]3 and (OEt)3SiPhSi(OEt)3. The as-prepared Rh(â… )-PPh2-PMO(Ph) exhibited matchable catalytic efficiency with the corresponding Rh(PPh3)3Cl homogeneous catalyst in water-medium reaction between phenylboronic acid and butyl acrylate or the 1, 4-conjugate addition reaction between phenylboronic acid and N, N-dimehytlacyrlmaide, which could be attributed to the high dispersion of Rh(â… ) active sites, the ordered mesoporous channels and the strong surface hydrophobicity resulted from phenyl fragments embedded in silica walls, leading to the facilitated the diffusion and the adsorption of organic molecules onto the catalyst in aqueous solution. The Rh(â… )-PPh2-PMO(Ph) could be used repetitively, showing the excellent durability which could be attributed to the effective inhibition of Rh(â… ) leaching and the high hydrothermal stability of the mesoporous structure.3. PPh2-functionalized mesoporous phenol-formaldehyde resin is synthesized by F127-directed co-polymerization between p-PPh2-phenol, phenol and formaldehyde, followed by coordination with metallic ions, leading to a new class of heterogenized organometallic catalysts (M-PPh2-MPs, M= Pd2+, Au+, Rh+ and Ni2+). These catalysts exhibit comparable efficiencies with the corresponding homogeneous catalysts in water-medium Barbier reactions, Sonogashira reactions, A3-Coupling reactions, Heck reactions and could be used repetitively.4. Using surfactant as structure directing agent, phenol, formaldehyde, piperazidine functionlized aldehyde as building blocks, Piperazidine-MPs was prepared by evaporation induced self-assembly (EISA) method. The sample exhibited ordered hexagonal mesoporous structure, large surface area. As Lewis solid base, the Piperazidine-MPs catalyst displayed comparable activity with the corresponding homogeneous catalyst in water media Knoevenagel and could be reused more than 6 times.