Synthesis and characterization of large-pore periodic mesoporouis organosilicas

Abstract

In this work, the synthesis of high-quality methylene-, ethylene-, and ethenylenebridgedSBA-15 type periodic mesoporous organosilicas with superior electronirradiation resistance was investigated. By employing the characterization techniquesof SAXS, FE-SEM, TEM and N2 sorption analysis, the porous properties and externalmorphologies of ethylene-bridged SBA-15 PMOs prepared under a variety ofsynthetic conditions were characterized and compared with that of mesoporous silicassynthesized under similar conditions. A nucleation-accretion mechanism based onrodlike organosilicate-micelle building blocks was proposed to explain the formationof various morphologies. The inductive, bridging and steric effects of the organicspacers of bridged silsesquinoxanes on the formation of large-pore PMOs wereidentified. In addition, by simply adjusting the HCl/H2O molar ratios, the micro-,meso-, and macro-porosities of the ethylene-bridged SBA-15 PMOs can be finelytuned without an obvious effect on their structural order.