Abstract
New approaches for β-cyclodextrin-containing silicas synthesis were demonstrated. Materials with hexagonally ordered mesoporous structure were prepared by postsynthesis grafting and by co-condensation methods. β-Cyclodextrin activated by a N,N′-carbonyldiimidazole was employed for postsynthesis treatment of 3-aminopropyl-modified MCM-41 support as well as for sol-gel synthesis with β-cyclodextrin-containing organosilane and tetraethyl orthosilicate participation in the presence of cetyltrimethylammonium bromide. The successful incorporation of cyclic oligosaccharide moieties in silica surface layer was verified by means of FT-IR spectroscopy and chemical analysis. Obtained β-cyclodextrin-containing materials were characterized by X-ray diffraction, transmission electron microscopy, and low-temperature adsorption-desorption of nitrogen. In spite of commensurable loading of β-cyclodextrin groups attained by both proposed approaches (up to 0.028 μmol · m–2), it was found that co-condensation procedure provides uniform distribution of β-cyclodextrin functionalities in silica framework, whereas postsynthesis grafting results in modification of external surface of silica surface. Adsorption of benzene from aqueous solutions onto the surface of β-cyclodextrin-containing materials prepared by co-condensation method was studied as the function of time and equilibrium concentration. Langmuir and Freundlich models were used to evaluate adsorption processes and parameters. Adsorption experiments showed that β-cyclodextrin-containing silicas could be promising for the trace amount removal of aromatics from water.
Highlights
M41S are ordered mesoporous materials with welldefined uniform pores, high surface area and pore volume, which have attracted great interest since 1992
Postsynthesis modification of silica surfaces was successfully realized by attachment of β-cyclodextrin or its derivatives to the silica support preliminary functionalized with N-(2-aminoethyl)-3-aminopropyl [29], carboxylated cuccinyl [30], 3-aminopropyl [31,32,33,34,35], 3-glycidoxypropyl [36, 37], hydrosilyl [38], ester [39], and 3-mercaptopropyl [40] groups, whereas the taken attempts to introduce β-cyclodextrin moieties into the silica framework by Trofymchuk et al Nanoscale Research Letters (2016) 11:174 sol-gel methods involve the condensation of silica alkoxides with β-cyclodextrin [41] or β-cyclodextrin-containing silanes [42,43,44]
0.80 covalent bond formation or sol-gel synthesis using βcyclodextrin-containing silane in the presence of ionic template. β-Cyclodextrin activated by N,N′-carbonyldiimidazole was employed for both synthetic approaches
Summary
M41S are ordered mesoporous materials with welldefined uniform pores, high surface area and pore volume, which have attracted great interest since 1992. Postsynthesis modification of silica surfaces was successfully realized by attachment of β-cyclodextrin or its derivatives to the silica support preliminary functionalized with N-(2-aminoethyl)-3-aminopropyl [29], carboxylated cuccinyl [30], 3-aminopropyl [31,32,33,34,35], 3-glycidoxypropyl [36, 37], hydrosilyl [38], ester [39], and 3-mercaptopropyl [40] groups, whereas the taken attempts to introduce β-cyclodextrin moieties into the silica framework by Trofymchuk et al Nanoscale Research Letters (2016) 11:174 sol-gel methods involve the condensation of silica alkoxides with β-cyclodextrin [41] or β-cyclodextrin-containing silanes [42,43,44]. Usage of aggressive solvents and activating agents in multistep procedures of organic reactions at postsynthesis treatment as well as functional silanes and pore-expanding agents at sol-gel condensation process may affect the structure of final MCM-41-type materials substantially causing damage of their hexagonally ordered pore structure. The activation properties of N,N′-carbonyldiimidazole in the reaction with β-cyclodextrin for the following immobilization of oligosaccharide derivative onto aminopropyl silica surface was used
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