Direct formation of hydrophobic silica-based micro/mesoporous hybrids from polymethylhydrosiloxane and tetraethoxysilane
Introduction
Since the discovery of surfactant-templated mesoporous materials in the early 1990 [1], [2], [3], the organic–inorganic silica-based mesoporous nanocomposite materials have attracted much interest because of their wide applications in the fields of catalysis and environmental remediation [4]. Generally speaking, the family of organic–inorganic silica-based mesoporous materials includes mesoporous materials with the Si–O–Si tetrahedron frameworks and surfaces functionalized with chemically bonded organic groups, mesophases with organicsilica frameworks, and mesoporous silicas with occluded organic materials such as polymers [4], [5].
Hierarchically structured porous materials containing both micro and mesoporosity have attracted significant attention owing to their important role in the systematic study of structure–property relationship and their technological promise in applications [6], [7]. With the successful synthesis of zeolite faujasite (FAU) and MCM-41, Kloetstra et al. [8] have obtained a composite of FAU and MCM-41 with the overgrowth of a thin layer of MCM-41 on FAU, and some good results were achieved using this composite for vacuum gas oil cracking. Karlsson et al. [9] have prepared some composite materials by simultaneous synthesis of MFI/MCM-41 phase by using two-template approach at the optimized template concentrations and reaction temperatures. Furthermore, Li et al. [10] prepared a MCM-41/β composite by a two-step crystallization, which has dual acidity and pore structure. Recently, several methyl-modified mesoporous materials have been successfully synthesized with dual porosity using non-ionic surfactant [11] in our research group. Although significant progress has been made on the synthesis of micro/mesoporous materials, to the best of our knowledge, there are no reports on the bimodal materials with micro/mesopores using non-surfactant route, not to mention preparing hydrophobic hybrids.
Polymethylhydrosiloxane (PMHS) is a silicon industry by-product, which is cheap, nontoxic and stable to air and moisture, and it can transfer its hydrides to a variety of metal catalysts (including Sn, Ti, Zn, Cu and Pd) that can then participate in a wide range of reduction [12]. At present, PMHS has mainly been employed as a reducing agent to reduce halogen, ketones, ethers, imines, and phosphine oxides. For example, ketones can be reduced into chiral alcohols with PMHS in the presence of zinc-chiral diamines, cadmium/bisoxazoline catalysts or copper/chiral diphosphines [13], [14]. Furthermore, chiral imines can be obtained from imines using PMHS as a reducing agent with the appearance of some catalysts such as titanocene complex, ZnCl2, Ti(OiPr)4, and zinc-diamine complex [14], [15], [16].
Here, we report the synthesis of organic–inorganic micro/mesoporous xerogels using mixed TEOS and PMHS as silica sources without additional introduction of any surfactants. To our interest, though neither solvent extraction nor calcination was utilized, the present amorphous samples exhibited high specific surface areas, pore volumes, bimodal pore structure and super hydrophobicity. Furthermore, the relative content of micropore and mesopore could be finely tuned by adjusting the mass ratio of PMHS to TEOS. It can be deduced that PMHS not only is one part of silica sources, but also plays a more important role of structure-directing agent.
Section snippets
Experimental
All the chemical agents were used as received without further purification. Polymethylhydrosiloxane (PMHS) (99%, ) was supplied by Acros. Tetraethoxysilane (TEOS, 99%), ethyl alcohol (anhydrous) and sodium hydroxide (NaOH) were provided by Tianjin chemical corporation.
In a typical synthesis, 1.57 mL (1.5587 g), 2.82 mL (2.8056 g), and 4.70 mL (4.676 g) PMHS were dripped into three typical flasks containing 70 ml ethanol, respectively. The resultant solutions were further stirred for 48 h
Bimodal structure determination
The nitrogen adsorption isotherms for the series of xerogels all clearly exhibit a resolved type IV isotherm with a steep desorption branch and a type H2 (type Ein de Boer classification) hysteresis loop [17] (see Fig. 1(a)), and Fig. 1(b) is the corresponding Barrett–Joyner–Halenda (BJH) pore size distributions. It can be clearly seen that the three distributions all mainly center at ∼3.9 nm. Taking the tensile strength effect (TSE) [18] into consideration, that is, the current pore data ∼3.9 nm
Conclusions
This preliminary research work shows that silica-based bimodal micro/mesoporous hybrids with high content of organic functionality could be easily prepared without additional introduction of any surfactants. Furthermore, characterization results indicate that the physico-chemical properties such as specific surface area, pore volume, pore size, relative content of micropore and mesopore could be finely controlled, and they all exhibit super hydrophobicity. More detailed investigation suggests
Acknowledgements
Financial supports from the national key native science foundation (20133040) and State Key Program for Development and Research of China (2005CB221402) and Australian Research Council are gratefully acknowledged.
References (34)
- et al.
Micropor. Mater.
(1996) - et al.
Micropor. Mesopor. Mater.
(1999) - et al.
J. Non-Cryst. Solids
(2005) - et al.
Tetrahedron Lett.
(2000) - et al.
Tetrahedron
(1997) - et al.
Micropor. Mesopor. Mater.
(2003) - et al.
Coll. Surf. A
(2001) - et al.
J. Mol. Catal. A
(2005) - et al.
Stud. Surf. Sci. Catal
(2002) - et al.
J. Non-Cryst. Solids
(2003)
Nature
J. Am. Chem. Soc.
Bull. Chem. Soc. Jpn.
Chem. Mater.
Chem. Mater.
Scinece
J. Am. Chem. Soc.
Cited by (47)
Application and evaluation of a new blend of biocides for biological control on cultural heritages
2023, International Biodeterioration and BiodegradationNanosilica:Polycaprolactone ratio and heat treatment modify the wettability of nanosilica/polycaprolactone coatings for application in aqueous systems
2022, Surfaces and InterfacesCitation Excerpt :Tetraethoxysilane-TEOS (98%, Sigma-Aldrich), polymethylhydroxysilane-PMHS (viscosity of 15–40 mPa∙s at 20 °C, Sigma-Aldrich), NaOH (P.A., Fmaia), sodium lauryl sulfate - LSS C12H25NaO4S (min 90%, Vetec), polycaprolactone - PCL (Mw 80,000 g⋅mol-1, Sigma-Aldrich), dichloromethane - DCM CH2Cl2 (99.5%, Sigma-Aldrich), trehalose C12H22O11.H2O (PA, Vetec), dimethylsulfoxide - DMSO (CH3)2SO (PA, Dynamics and ethyl acetate CH3COOCH2CH3 (PA, Dynamics and ethanol (P.A., Dynamics) were purchased from local suppliers and its representations. The synthesis procedures of the silica nanoparticles followed the methodology adapted from Yang et al. [21]. A volume of 2.82 mL (2.80 g) of PMHS was dripped into 70 mL of ethanol in a beaker and then 0.008 g of NaOH was added and stirred constantly at room temperature for 48 h so that the PMHS could react with part of the ethanol.
Absorption of organic compounds by mesoporous silica discoids
2020, Microporous and Mesoporous MaterialsA new preventive coating for building stones mixing a water repellent and an eco-friendly biocide
2018, Progress in Organic CoatingsIn-situ addition of graphene oxide for improving the thermal stability of superhydrophobic hybrid materials
2017, PolymerCitation Excerpt :Yang et al. synthesised a non-template superhydrophobic micro-mesoporous hybrid using PMHS and tetraethoxysilane (TEOS) and reported that more than one week was needed to reproduce the superhydrophobic hybrid micro/mesoporous material [23–25]. PMHS exhibited self-hydroxylation and condensation properties in sodium hydroxide solutions [11,23–25]. Therefore, superhydrophobic mesoporous material were synthesised in a one-pot process (within 2–3 days) using PMHS (without a cross-linking agent and surfactant).