| In recent years, mesoporous silica nanoparticles with center-radial pore channels have potential application in adsorption, separation, catalysis, and biomedicine, due to its large open mesopores, high specific surface area and nanoscale particle size. Meanwhile, the spherical channel, especially the particle size less than 100 nm is more close to the metal enzyme nano cavity, and a shorter channel length is more conducive to diffusion of the silylating agent functional group and subsequently the function of the reaction, is expected to become a good carrier for imitation enzyme catalyst. Although work in this area already has a certain research progress, but how simple, large-scale and green synthetic DMSNs having different particle size and high hydrothermal stability remains a challenge. Based on the abundant literature investigations and our preliminary studieson the synthesis of mesoporous materials, in this article the synthesis, mechanism, function and functional groups surrounding environment influence on the catalytic activity of functional groups did exploratory work. The main results are listed as follows:1. By adjusting the silicon source, alkali source and the type of surfactant and pH value change tracking system in situ in the course of the preparation of material. We know that the hydrolysis rate faster silicon source of TMOS join can significantly reduce DMSNs particle size, but the presence of TEOS is DMSNs prerequisite. Types of small molecules alkaline source has a significant effect on the particle size, but not much impact on the pore structure of the material. The counter ion of Surfactants strength of the force of CTA+ has an important influence on the formation of the final material. According to the result of material characterization and system pH, we proposed a spherical micelle templating mechanism.2. Pure silicon mesoporous material having a large number of surface silanol groups, it can be functionalized with silane reagent, and due to the hydrophilic of silanol there will has physical absorption water in the pores. In this chapter we use after grafting methods using N-(2-aminoethyl)-3-amino-propylsilyl (AAPMS) as probe molecule with different mesoporous materials with different morphology and pore structure, and in the process of functional to incorporate different Hofmeister series of anionic ammonium salt. Detailed study of the effects of the presence of weak interactions within the pores of the micro-environment (network of hydrogen bonds, hydrophilic and hydrophobic), effects on catalytic activity and then research the change surrounding microenvironment of the active site. Henry reaction acting as probe reaction. The conversion and selectivity changes of Henry reaction revealed that there is a clear correlation between the catalytic activity of functioned DMSNs and Hofmeister series, but there is no clear correction between the catalytic activity of functioned SBA-15 and Hofmeister series. In the contrast, there is reverse trend of functioned Z-SiO2. In conclusion the DMSNs with center-radial pore channels has good nano confined effect, The introduction of Hofmeister series anion can adjust the hydrogen bond network in the mespores, then affect the catalytic activity of the catalyst.3. Using Small molecule amine with the intermediate is a hydrophobic group and the both end is hydrophilic group as catalyst, Henry reaction as probe reaction, introducing different Hofmeister series anion in the reaction. Reaction results show that Hofmeister series anions exhibit the opposite effect in ethylenediamine (EDA) or phenylenediamine (PDA) and DMSNs. But the effect in Decamethylenediamine (DDA) and hexadecylamine (HA) has good consistend with DMSNs. Experimental results show that with a long carbon chain amine molecules in the reaction solution will exist in a state of reverse micelles, a similar form of mesoporous nano-micellar confinement environment, and thus exhibit catalytic activity consistent with DMSNs. |
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