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Ordered cage-like mesoporous materials were synthesized and characterized in terms of their surface, structural and adsorption properties. This dissertation covers three major topics devoted to the synthesis of cage-like silicas and organosilicas. The first topic involves the improvement of synthesis conditions of cage-like silicas such as SBA-16 and FDU-1. Special emphasis was given to the study of influence of different synthesis parameters, such as variations of the TEOS/template ratio, inorganic salt, the self-assembly time, and template removal procedure. It was shown that in order to obtain FDU-1 with uniform pore entrances, large cage diameter and high pore volume, optimal triblock copolymer/silica and salt/template ratios should be within 135:1 and 2.5:1, respectively. In addition, the first synthesis step can be shortened to six hours of the original 24 without diminishing the quality of the resulting FDU-1 materials. A two-step template removal method that combines partial extraction and temperature-controlled calcination was demonstrated to be an effective way for complete removal of the template.The second topic includes the fabrication and characterization of cage-like organosilicas with pendant groups, namely, vinyl, mercaptopropyl, ureidopropyl and imidazole. These organosilicas were prepared by co-condensation of desired organosilane and tetraethyl orthosilicate (TEOS) using the optimal synthesis procedures established for pure silicas. The co-condensation synthesis afforded materials with high loadings of organic groups up to 40%, large pore diameters, and narrow pore size distributions (PSDs). Moreover, the structural transformation from cubic to hexagonal was observed under low acidic conditions, double amount of polymer, and the addition of sodium chloride.The third topic involves the incorporation of bulky isocyanurate bridging groups into periodic mesoporous organosilicas (PMOs) using tris[3-(trimethoxysilyl)propyl]isocyanurate and TEOS. The resulting PMOs possess up to 30% of bridging groups, large pore volume and high surface area. The extraction, however, was insufficient to completely remove the template. An additional heating of extracted PMOs, therefore, was carried out to remove the remaining polymer. The aforementioned materials were characterized by nitrogen and argon adsorption, powder X-ray diffraction, transmission electron microscopy, elemental analysis, high resolution thermogravimetry, and Fourier-transform infrared spectroscopy. |
