Adsorption and structural properties of channel-like and cage-like organosilicas |
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Authors: | Rafal M Grudzien Bogna E Grabicka Mietek Jaroniec |
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Institution: | (1) Department of Chemistry, Kent State University, Kent, Ohio 44242, USA |
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Abstract: | Channel-like and cage-like mesoporous silicas, SBA-15 (P6mm symmetry group) and SBA-16 (Im3m symmetry group), were modified by introducing single ureidopropyl surface groups, mixed ureidopropyl and mercaptopropyl surface
groups, and single bis(propyl)disulfide bridging groups. These hexagonal and cubic organosilicas were prepared under acidic
conditions via co-condensation of tetraethyl orthosilicate (TEOS) and proper organosilanes using poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) amphiphilic block copolymer templates, P123 (EO20PO70EO20) and F127 (EO106PO70EO106). The modified SBA-15 and SBA-16 materials were synthesized by varying the molar ratio of organosilane to TEOS in the initial
synthesis gel. The removal of polymeric templates, P123 and F127, was performed with ethanol/hydrochloric acid solution. In
the case of SBA-15 the P123 template was fully extracted, whereas this extraction process was less efficient for the removal
of F127 template from the SBA-16-type organosilicas; in the latter case a small residue of F127 was retained. The adsorption
and structural properties of the resulting materials were studied by nitrogen adsorption-desorption isotherms at −196∘C (surface area, pore size distribution, pore volumes), powder X-Ray diffraction, CHNS elemental analysis and high-resolution
thermogravimetry. The structural ordering, the BET specific surface area, pore volume and pore size decreased for both channel-like
and cage-like mesoporous organosilicas with increasing concentration of incorporated organic groups. |
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Keywords: | Channel-like mesostructures Cage-like mesostructures Ordered mesoporous organosilicas Nitrogen adsorption SBA-15 SBA-16 Co-condensation synthesis Ureidopropyl surface group Mercaptopropyl surface group Bis(propyl)disulfide bridging group |
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