Synthesis and characterization of periodic porous benzene-silica hybrid powders with cubic and hexagonal symmetries
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Synthesis and characterization of periodic porous benzene-silica hybrid powders with cubic and hexagonal symmetries. Valérie Goletto1, Anne-Claire Bled1, Gregor Trimmel1, Michel Wong Chi Man2, Hee-Gweon Woo3, Dominique Durand4 and Florence Babonneau1* 1 Chimie de la Matière Condensée, UPMC/CNRS, Paris, France. [email protected] 2 Département de Chimie Organique Fine, Université de Montpellier II, France. 3 Dept. of Chemistry, Chonnam National University, Kwangju, Korea 4 LURE, Université Paris-Sud, Orsay, France ABSTRACT Organosilica powders with uniformly distributed bridging benzene groups have been synthesized from the condensation of bis- or tris-(triethoxysilyl)benzene in the presence of cetyltrimethylammoniumbromide. The syntheses were performed under strong acidic conditions and the organic groups were always incorporated without cleavage of the Si-C bonds as indicated by solid state MAS NMR studies. Depending on the nature of the precursors, materials with different ordering were obtained : a 2D-hexagonal (p6m) phase was formed from the 1,3bis(triethoxysilyl)benzene, whereas the 1,4-bis(triethoxysilyl)benzene lead to a cubic Pm3n phase. The surfactant was removed either by solvent extraction or by controlled calcination, which did not affect the mesostructure of the materials.
INTRODUCTION The surfactant-template route discovered in the early nineties to prepare silicates with ordered porosity has now been extended to the synthesis of a variety of periodic mesoporous organosilicates (PMOs) [1, 2]. They can be decomposed in two main families, depending on the number of bonds between the organic group and the silicate framework : one for a pendant group that will act as a network modifier, and two or more for a bridging group, that will behave as a network former. A large number of studies have been devoted to the first group of materials, prepared from trialkoxysilanes, RSi(OR')3. Two general strategies have been used, either a postsynthesis procedure consisting of a direct grafting of a suitable organosilane on the silica surface or a direct one-pot synthesis based on co-condensation reactions of an organosilane with a tetraalkoxysilane in the presence of surfactant. More recently, an entirely new family of PMOs has been described, prepared from bis(silylated) (R'O)3Si-R-Si(OR')3 precursors, in which the organic groups are an integral part of the pore walls [3-5]. Changing the organic group R allows to introduce a wide variety of different organic species, and therefore allows further tunability of the mechanical, thermal, or optical properties of the resulting hybrid materials [6]. In the few years since their discovery, a number of different bridging groups R have been successfully introduced, like R = CH2 [7], CH2CH2 [3,4,8-10], CH=CH [4,5], C≡C [11], benzene [11,12], thiophene [11], bithiophene [11], ferrocene [11] and viologene units [13]. Even PMOs with two differently bonded organic groups, pendant as well as bridging units, have been synthesized [14]. Most of the samples have been prepared with cati
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