Direct synthesis of cubic benzene-bridged mesoporous organosilica functionalized with mercaptopropyl groups as an effective adsorbent for mercury and silver ions

Hao Yiang Wu, Ching Ting Chen, I. Ming Hung, Chia Hsiu Liao, Shanmugam Vetrivel, Hsien Ming Kao

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31 Scopus citations

Abstract

Well-ordered cubic (Pm̄3n symmetry) benzene-bridged periodic mesoporous organosilicas (PMOs) functionalized with variable contents of thiol groups were successfully synthesized via a one-step co-condensation of 1,4-bis(triethoxysilyl)benzene (BTEB) and 3-mercaptopropyltrimethoxysilane (MPTMS) in a highly acidic medium with use of cetyltrimethylammonium bromide (CTMABr) as the structure-directing agent. The materials thus obtained exhibited ordered and uniformed mesopores up to 25 mol % of MPTMS in the initial mixture. Direct evidence of the simultaneous presence of chemically attached thiol and benzene moieties was provided by solid-state 29Si and 13C NMR spectroscopy. The present cubic PMOs can be synthesized with a wide temperature window from 0 to 100 °C without any undesirable phase transformation. On the contrary, this is not possible when BTEB was replaced by tetraethoxysilane (TEOS) as the silicon source for the conventional synthesis of SBA-1 with Pm̄3n symmetry. It suggests that the benzene-linking spacer of BTEB has a beneficial effect on the enlargement of effective head group of the surfactant against the temperature changes and thus prevents phase transformation to a hexagonal mesophase. These thiol-functionalized benzene-silica materials exhibited high adsorption affinity toward metal ions such as Hg2+ and Ag+, but not for Cd2+, Co 2+, and Pb2+. Of particular interest is that the 13C NMR chemical shift of the carbon atom adjacent to the -SH group is sensitive to the Hg2+ and Ag+ ion bindings, shifting from 27 ppm to 37 and 34 ppm, respectively. Such a significant NMR shift provides clear evidence that there are strong interactions between the thiol groups and the Hg2+ and Ag+ ions.

Original languageEnglish
Pages (from-to)7021-7029
Number of pages9
JournalJournal of Physical Chemistry C
Volume114
Issue number15
DOIs
StatePublished - 22 Apr 2010

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