One-pot synthesis of mesoporous organosilicas using sodium silicate as a substitute for tetraalkoxysilane (original) (raw)
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Direct synthesis of mesoporous organosilica from sodium silicate and organotrialkoxysilane
Journal of Materials Science Letters, 2003
A variety of ordered mesoporous materials have been synthesized by a template method using supramolecular assembly of the surfactant molecules, however, many applications (such as adsorption, ion exchange, catalysis and sensing) require materials of specific surface function. In order to introduce functionality into these mesoporous materials, organic modification techniques are enjoying a renewed interest. Recently, much work focused on one-step synthesis of mesoporous structure containing covalently linked organic functionalities [8][9][10]. The primary approach was that expensive trialkoxysilane, such as tetrethoxysilane, and organotrialkoxysilane precursors were mixed at the first step, then the obtained mixture co-condensed in the presence of a surfactant. In some instances the organotrialkoxysilanes with small organic groups can enter framework walls of the mesostructures in the co-condensation [10], the presence of only three hydrolyzable Si OR bonds in intraframework is likely to impede the complete cross-linking of the silica network, resulting in the perturbation in the framework ordering. Here we report the preparation of MSU-type mesoporous organosilica from inexpensive sodium silicate (Na 2 SiO 3 · 9H 2 O) and organotrialkoxysilane. This method, which we called "step by step," greatly reduced the possibility that organotrialkoxysilanes enter framework walls of the mesostructures. Furthermore, to the best of our knowledge, this was the first preparation of mesoporous organosilica from sodium silicate and organotrialkoxysilanes, it perhaps opens up the field of large-scale preparation for these materials.
New Route to Mesoporous Silica via a Silsesquioxane Precursor
Ceramics - Silikaty, 2018
The effect of the addition of octakis(tetramethylammonium)-t8-silsesquioxane (octaanion) on the modification of the porous structure of the silica gel obtained by the sol-gel method catalysed by acetic acid was studied. The obtained silica gel was characterised by the low-temperature nitrogen adsorption/desorption method (BET), powder diffraction (XRD), thermogravimetry (TG) and microscopic observations (TEM). The octaanion was found to act as a textural promoter, as evidenced by almost a 25 % increase in the surface area of the obtained silica. As a result of the stabilisation in the porous structure of the silica gel, the tetramethylammonium groups of the octaanion show higher thermal stability than the groups present in the octaanion structure or those introduced in the form of tetramethylammonium hydroxide. Tetramethylammonium ions were proved to show increased thermal resistance, which is related to the porous properties of the SiO 2 matrix.
Synthesis of pore-enlarged mesoporous organosilicas under basic conditions
Microporous and Mesoporous Materials, 2004
A series of mesoporous organosilicas (MOs) in the ½3:2; 11:1 nm pore diameter range has been obtained in basic media by using 1,2-bis(triethoxysilyl)ethane (BTEE) or 1,2-bis(trimethoxysilyl)ethane (BTME) as a silica source, binary surfactant mixtures [CH 3 (CH 2 ) 17 NMe 2 (CH 2 ) 3 NMe 3 ] 2þ 2Br À (C 18-3-1 ) and [CH 3 (CH 2 ) 15 NMe 3 ] þ Br À (C 16 TABr) as structure-directing agents (SDAs), and TMB (mesitylene) or TPB (1,3,5-triisopropylbenzene) as swelling agents. Pore size control has been achieved via variation of (i) the binary surfactant ratio, (ii) base (sodium hydroxide) concentration, (iii) reaction time and temperature, and (iv) type of expander molecule. The surface morphology and silanol population of the dehydrated MOs was examined by TMDS (tetramethyldisilazane) silylation. The parent and functionalized MOs were characterized by powder X-ray diffraction, N 2 physisorption, elemental analysis, FTIR, and solid-state ( 1 H, 13 C, 29 Si) NMR spectroscopy. According to their PXRD patterns, the pore-enlarged MO materials do not display any long-range order, however, pore volumes >2 cm 3 /g. The type of hysteresis loop exhibited by the N 2 adsorption and desorption isotherm changed remarkably for MOs synthesized at low concentrations of divalent surfactant as well as base, which can be attributed to a change of pore topology. 29 Si MAS NMR spectroscopy revealed the prominent T 2 and T 3 peaks at )58and)58 and )58and)64 ppm, respectively, indicative of an intact wall and surface structure. The silyl group coverage was determined as 0.8-1.3 SiHMe 2 groups per nm 2 corresponding to approximately half of that found on purely siliceous periodic mesoporous silicas such as MCM-41 or MCM-48.
Mesoporous silica obtained by polycondensation of octahydridooctasilsesquioxane
Journal of Materials Science, 2013
Mesoporous silica, due to its porosity and morphological features, have been considered a fascinating material for many technological applications. In this report, we describe the preparation of a structurally stable mesoporous silica material using octahydridooctasilsesquioxane (T 8 H ). The structure and properties of final samples were determined by XRD, FT-IR, and TEM methods. Structural analysis has shown that the siliceous material is amorphous but mesoporous. BET surface area, pore volumes, and pore size distribution were measured using nitrogen sorption methods-data were collected from the adsorption branch using BJH method for mesopores and t-plot method for micropores. It was found that the cage-type structure of T 8 H molecules and the process conditions determine the specific morphology of the cross-linked products. Completely inorganic, mesoporous silica of a narrow pore distribution was obtained. It was found that the materials have large surface area and pores in the meso range (2-5 nm). The amount of mesopores and the characteristic surface area of the prepared samples strongly depended on the reaction conditions.
Chinese Journal of Chemistry, 2010
Sodium silicate from rice husk ash (RHA) was transformed to functionalized silica with 3-(mercaptopropyl)trimethoxysilane (MPTMS) or 3-(aminopropyl)triethoxysilane (APTES) via a simple sol-gel technique in a one-pot synthesis to give RHAPrSH and RHAPrNH 2 . The 29 Si MAS NMR of RHAPrSH and RHAPrNH 2 showed the presence of T 1 , T 2 , T 3 , Q 2 , Q 3 and Q 4 silicon centers. The 13 C MAS NMR showed that RHAPrSH had chemical shifts at δ 16.59, 32.73, consistent with two of the carbon atoms of the MPTMS moiety, while the 13 C MAS NMR of RHAPrNH 2 had chemical shifts at δ 14.58, 26.13, 47.87, consistent with the three carbon atoms of the APTES moiety. The presence of carbon, silicon, sulfur and nitrogen in RHAPrSH and RHAPrNH 2 was determined by a combination of elemental analysis and EDX study.
Mesoporous silica obtained with methyltriethoxysilane as co-precursor in alkaline medium
Applied Surface Science, 2017
Mesoporous silica particles have been synthesized by sol-gel method from tetraethoxysilane (tetraethylorthosilicate, TEOS) and methyltriethoxysilane (MTES), in ethanol and water mixture, at different ratios of the of the silica precursors. Ammonia was used as catalyst at room temperature and hexadecyltrimethylammonium bromide (cetyltrimethylammonium bromide, CTAB) as the structure directing agent. Nitrogen sorption, X-ray diffraction and small-angle neutron scattering gave information on the evolution of the gel structure and pore morphologies in the function of MTES/TEOS molar ratio. Thermogravimetric and differential thermal analysis showed that with addition of MTES the exothermic peak indicating the oxidation of the low molecular weight organic fragments shift to higher temperature. A room-temperature, one-pot synthesis of MCM-41 type materials is presented, in which the variation of the MTES concentration allows to change the hydrophobicity, preserving the specific properties materials, like the ordered pore structure, large specific surface area and high porosity, making them suitable for selective uptake of guest species in drug loading applications. Specifically, the obtained materials had cylindrical pores, specific surface areas up to 1101 m 2 /g and total pore volumes up to 0.473 cm 3 /g. The obtained mesoporous materials are susceptible for further functionalization to improve their selective uptake of guest species in drug delivery applications.
One-pot synthesis of organic polymer functionalized mesoporous silicas
Microporous and Mesoporous Materials, 2021
Polymer functionalization of ordered mesoporous silicas (OMS) offer wide applications owing to their synergy properties. In this study, a new approach for polymer functionalization of OMS is demonstrated by the co-condensation of silica precursor and a functional polymer bearing triethoxysilane end-group in the presence of a tailored poly(ethylene oxide)-b-polystyrene (PEO-b-PS) amphiphilic copolymer used as pore template. The novelty of this strategy resides in the co-micellization of PEO-b-PS and functional polymer that enables the incorporation of the latter into the mesoporous silica. By changing the nature of the functional polymer, as well as their loading concentration and process conditions, different ordered polymermesoporous silicas containing aryl, nitro or amide groups and high polymer content, up to 38 wt% were synthesized. These materials exhibit high specific surface area (488 m 2 g-1) and large pores (8 nm) with acceptable CO2 adsorption capacity and selectivity towards CH4 and N2.
Journal of Non-Crystalline Solids, 2006
A new polyether-inorganic hybrid mesoporous silica has been synthesized through in situ incorporation of hydroquinone (HQ) moiety bridging between two silica units using tetraethyl orthosilicate (TEOS) as silica source in the presence of the self assembly of cationic surfactant under acidic pH. Samples synthesized with TEOS:HQ mole ratio of 2.0 and 4.0 showed good organic loading, mesoporosity and stability. Decreasing this ratio to 1.0 resulted in a organic-rich mesoporous hybrid material, which collapsed during template removal, whereas, increasing this ratio to 8.0 resulted in very poor incorporation of hydroquinone in the mesoporous silica. XRD and N 2 sorption data suggested the mesopore structure. TEM images indicated the wormhole like structure of these mesoporous samples. Solid state NMR data suggested the existence of (-O-C 6 H 4-O) 2 Si * (OSi) 2 and (-O-C 6 H 4-O)Si * (OSi) 3 sites in addition to (Si * (OSi) 4) sites. UV-Visible and FT-IR data suggested the incorporation of hydroquinone species and Si-O-Ph bonding in the samples.
1999
A novel synthetic route for the preparation of the porous silica by a supramolecular templating mechanism is reported. By depositing the precursor solution containing tetramethoxysilane and hexadecyltrimethylammonium chloride on glass plates at an elevated temperature (60 • C), mesostructured silica-hexadecyltrimethylammonium chloride composites with the size of a few mm to a cm have been prepared. The composition of the resulting products can be controlled by simply changing the composition of the starting mixtures. By the calcination of the as synthesized mesostructured materials, porous silica with large surface area was obtained. Due to the ease of operation, the present method is a simple way to prepare porous silica alternative to the procedures reported for the preparation of mesoporous silicas (MCM-41 and FSM-16).
One-pot synthesis of bimodal (macro-meso, micro-mesoporous) silica by polyHIPE: parameter studies
Journal of Porous Materials, 2019
Porous silica with hierarchical organization of pore structure is desired for a variety of applications such as, chromatography, sensing, control release, scaffold for biomedical applications and catalysis. Highly porous polymers obtained from high internal phase emulsion (HIPE) templating route have attracted increasing attention of researchers due to their hierarchical porous and interconnected structure with high porosity and low density. The novel method adopted in our approach combines redox initiated polymerization using HIPE polymerization and an in-situ sol-gel processing technique followed by calcination to obtain highly porous materials. The obtained materials have reminiscent of polyHIPE morphology containing pores and interconnected pore throats in micrometer size range with mesopores on the wall of macropores. The effect of concentration of TEOS, volume of dispersed phase, crosslinker concentration, shear rate and surfactant concentration as well as variation in calcination temperatures on the properties of silica materials were examined.