Synthesis, Characterization And Application Of Functionalized Periodic Mesoporous Organosilicas

Organic bridged hybrid mesoporous materials named periodic mesoporous organosilicas (PMOs) were reported by three groups independently in 1999. These materials contain the organic groups as an integral part of the inorganic-oxide framework and the inorganic and organic moieties are covalently linked to each other. Hence, the "chemistry of the void space" explored by the classical MCM-41-type materials was extended to the "chemistry of the walls". This novel route offers materials with some important features that cannot be obtained by other approaches.The current contribution concerns the synthesis, characterization and application of bi-functionalized and mutil-functionalized organic-inorganic hybrid mesoporous silicas. The synthesized materials were further characterized by XRD, nitrogen sorption analysis, ²⁹Si MAS NMR and ¹³C CP MAS NMR technique, thermogravimetric analysis, UV-Raman and FT-IR spectroscopy etc. The applications in catalysis and adsorption were studied in detail. Finally, we synthesized mutil-functional periodic mesoporous organosilicas successfully. The effect of organic group was studied.Using nonionic oligomeric and triblock copolymers Brij-76 and P123 as surfactant for the synthesis of thiol functionalized ethane-silicas, the materials have different BET surface area and pore volume and the diameter from 1.5 to 6 ran. The maximum content of the attached thiol group in the mesoporous framework is 2.48 mmol/g. The ordered mesoporous materials are efficient heavy metal ions adsorbents, the maxium adsorption amount of Hg²⁺ is 455 mg/g. The large and uniform pore structures are one of the most important factors for propylthiol functionalized mesporous materials to be efficient heavy metal ions adsorbent. The mutil-functional adsorbents are efficient to remove various kinds of heavy metal ions such as Hg²⁺, Cd²⁺, Zn²⁺, Cu²⁺, and Cr³⁺ from wastewater.Compared to zeolites, the acidity of the mesoporous is relatively low which greatly limited their applications. We synthesis of sulfonic functionalized periodic mesoporous organosilicas by H₂O₂ (30 wt %) in-situ oxidized -SH to -SO₃Hduring the condensation process. The highest acid exchange capacity (acid-base titration methods) could achieved was 1.72 H+ mmol/g. The catalytic properties of all materials were investigated by condensation and esterification reactions. All of the materials are efficient catalysts for the reactions. Results demonstrated that the organic moieties bridged in the framework played an important role on the catalytic activity and selectivity of the materials.It is noteworthy that multi-functional periodic mesoporous organosilicas have been successfully synthesized by the one-step condensation of three silica precursors in acidic medium for the first time. The role of the bridging ethane moieties on the hydrothermal stability of the mesoporous materials was also investigated. The catalytic activities of the materials were investigated in several reactions,, and the amounts of the ethane groups incorporated have great effect on their catalytic activity and hydrothermal stability.