Organosilica Precursor Research Articles

Facile synthesis of new periodic mesoporous organosilica and its performance of immobilizing horseradish peroxidase

A new class of periodic mesoporous organosilicas (PMOs), which contains various hydrophilic groups of –OH, –O– and –S–, is successfully synthesized with novel bridged organosilica precursor under the acid-catalyzed and inorganic-salt-assisted conditions. These hybrid materials possess the ordered mesostructure with uniform pore size distributions, thick framework walls, thermal stability and specific functional groups; and they are carefully characterized by XRD, N2 adsorption, TGA, FT-IR, TEM and NMR spectroscopies. Moreover, horseradish peroxidase (HRP) is immobilized on these new PMO composites for the first time, and their enzyme activity in the oxidation of 1,3,5-trimethylbenzene (TMB) is elevated in the range of 25–59% compared with that of free HRP in solution. Again, the HRP immobilized samples can be reused for many cycles, resulting from the interfacial activation of the enzyme when it is attached to the surface of hybrid hosts where is filled with organic groups and hydrophobic parts.

Family of Single-Micelle-Templated Organosilica Hollow Nanospheres and Nanotubes Synthesized through Adjustment of Organosilica/Surfactant Ratio

A family of hollow organosilica nanospheres and nanotubes was synthesized at appropriately low organosilica-precursor/block-copolymer-surfactant ratios. In Pluronic F127 (EO106PO70EO106) block copolymer templated synthesis of ethylene-bridged organosilicas in the presence of a swelling agent, the lowering of the organosilica-precursor/surfactant ratio led to a change from highly ordered face-centered cubic structure of spherical mesopores to individual hollow spherical nanoparticles. It was hypothesized that at low ratios of organosilica precursor to PEO-PPO-PEO, the framework precursor is solubilized in the micelles and its concentration on their surface is not sufficient to induce appreciable cross-linking between the resulting nanoobjects and the consolidation into larger particles. The inner pore size of the nanospheres was adjusted by varying the micelle expander, allowing us to obtain pore diameters up to ∼20 nm. By employing low precursor/surfactant ratios, hollow spheres of methylene-, ethenylene-...

Hydrophobic mesostructured organosilica-based thin films with tunable mesopore ordering

Hydrophobic mesostructured organosilica-based thin films with tunable mesoporosity offer promising opportunities for ultra low k applications. They are presently prepared by spin-on solutions and evaporation-induced self-assembly method (EISA) using polystyrene- b-polyethylene oxide block copolymers as structure-directing agents and methyltriethoxysilane (MTES) as organosilica precursor. With PS(1600)- b-PEO(1800) (between brackets is the molecular weights for blocks), different types of ordered mesostructures can be achieved by controlling the PS- b-PEO/MTES weight ratio, i.e. with Fm3m symmetry (evidenced for the first time in a organosilica film) and also with Im3m and P6mm space groups. Mesostructural ordering is characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and atomic force microscopy (AFM). The thin film porosity is analyzed using ellipsometric porosimetry (EP). Porogen removal and crosslinking of the organosilica network are followed by Fourier transform infrared spectroscopy (FTIR) and 29Si magic angle spinning nuclear magnetic resonance (MAS NMR). The effect of the molecular weight and the hydrophilic lipophilic balance (HLB) of the used block copolymers on the mesostructure ordering is finally investigated using different types of polystyrene- b-polyethylene oxide block copolymers.

Periodic Mesoporous Organosilicas with Controlled Pore Symmetries for Peptides Enrichment

Periodic mesoporous organosilicas (PMOs) with controlled structures have been synthesized by using cetyltrimethylammonium bromide (CTAB) and sodium perfluorooctanoate (PFONa) as co-templates, 1,2-bis (triethoxysilyl)ethane (BTEE) as an organosilica precursor. By increasing the weight ratio of PFONa/CTAB, a structure transformation from a cubic (Pm-3n) to a two-dimensional hexagonal (p6m) mesostructure and then to multilamellar vesicles can be observed. The cubic and hexagonal samples have similar particle size (200-750 nm), pore size (2.6 and 2.8 nm, respectively), total pore volume (approximately 0.7 cm3/g), and surface area (approximately 900 m2/g), providing ideal candidates to study the peptide enrichment performance influenced simply by pore symmetries. Matrix-assisted laser desorption ionization time-of-flight mass spectroscopy (MALDI-TOF MS) analysis indicates that PMO with a cubic (Pm-3n) structure is more effective in small molecular weight peptides enrichment compared with PMO with a hexagonal structure, showing the importance of mesostructural control for targeted applications. The phenomena can be attributed to the cage-type structure of the Pm-3n symmetry, which possesses cages with a relatively larger pore size and connectivity with a relatively smaller size. It is suggested that the pore entrances with small size are responsible for entrapping small molecular weight peptides. Our study may shed light on the designed synthesis of functional porous materials with controlled structures and enhanced performance in peptides enrichment.

ChemInform Abstract: From Molecular Chemistry to Hybrid Nanomaterials. Design and Functionalization

AbstractReview: 72 refs.

Periodic Mesoporous Benzene−Silicas Prepared Using Boric Acid as Catalyst

Highly ordered periodic mesoporous benzene−silicas with 2D p6mm symmetry were synthesized through sol−gel self-assembly in the presence of a nonionic poly(ethylene oxide)−poly(dl-lactic acid-co-glycolic acid)−poly(ethylene oxide) (PEO−PLGA−PEO, EO16(L29G7)EO16) triblock copolymer template using boric acid (weak Lewis acid) as a catalyst instead of strong hydrochloric acid. 1,4-Bis(triethoxysilyl)benzene (BTEB) was used as an organosilica precursor, and the reaction and aging temperatures were set at 40 and 100 °C, respectively. The molar concentration of boric acid was varied from 0.5 to 3 M to find the minimum acidity required and to check the effect of this acidic catalyst on the formation of benzene−silica mesostructures. This study shows that the ordered mesostructure of benzene−silica was observed even at 1 M concentration of boric acid ([B(OH)3]/[BTEB] = 12), and highly ordered hexagonal mesostructures were obtained at higher concentrations of this acid. Thermal stability of the benzene−silica mater...

New designs of hydrophobic and mesostructured Ultra Low k materials with isolated mesopores

ABSTRACTIn this work, hydrophobic mesostructured organosilica thin films, exhibiting isolated mesopores (~ 7 nm), have been successfully deposited by spin-coating using different polystyrene-block-polyethylene oxide copolymers (PS-b-PEO) as structure-directing agents and methyltriethoxysilane (MTES) as organosilica precursor. Different ordered mesostructures (Face Centered Cubic, 2D or 3D Hexagonal and Body Centered Cubic) can be achieved by controlling different synthesis parameters. X-Ray Diffraction (XRD) and Grazing Incidence Small Angle X-Ray Scattering (GISAXS) techniques were used to investigate the mesostructure evolution through thermal and UV treatments. Swelling and shrinkage were evidenced by in-situ XRD and X-Ray Reflectivity measurements during the thermal removal of the meso-templates. Infrared spectroscopy and 29Si NMR were additionally used to investigate the microstructure evolution. The film porosity was estimated thanks to Ellipsometry Porosimetry (EP). Correlation between mechanical properties through nanoindentation measurements and the mesostructure ordering is discussed as well as assessments of the dielectric constant k by mercury contact probe.

From molecular chemistry to hybrid nanomaterials. Design and functionalization

This tutorial review reports upon the organisation and functionalization of two families of hybrid organic-inorganic materials. We attempted to show in both cases the best ways permitting the organisation of materials in terms of properties at the nanometric scale. The first family concerns mesoporous hybrid organic-inorganic materials prepared in the presence of a structure-directing agent. We describe the functionalization of the channel pores of ordered mesoporous silica, that of the silica framework, as well as the functionalization of both of them simultaneously. This family is currently one of the best supports for exploring polyfunctional materials, which can provide a route to interactive materials. The second family concerns lamellar hybrid organic-inorganic materials which is a new class of nanostructured materials. These materials were first obtained by self-assembly, as a result of van der Waals interactions of bridged organosilica precursors containing long alkylene chains during the sol-gel process, without any structure directing agent. This methodology has been extended to functional materials. It is also shown that such materials can be obtained from monosilylated precursors.

Inkjet-Printing-Engineered Functional Microdot Arrays Made of Mesoporous Hybrid Organosilicas

The fabrication of three-dimensional fine-scale microdot arrays of organized mesoporous hybrid organosilicas by the coupling of inkjet printing (IJP) and Pluronic F127 driven evaporation-induced self-assembly (EISA) in the presence of cocondensed silica and organosilica precursors is demonstrated. The mesoorganization can be optimized by tuning both processing and chemical parameters (the drying time between successive layers, droplet volume, chemical composition, temperature, and aging time of the colloidal sol). The feasibility of one-pot multifunctionalization with both TFTS CF3(CF2)5CH2CH2Si(OC2H5)3 and thiol functionalities HSCH2CH2CH2Si(OC2H5)3 is also demonstrated, emphasizing the wide range of accessible nanostructured porous hybrid materials that result from the coupling of IJP and EISA. From this demonstrative concept, many hybrid materials with applications in the field of multiarray sensors and smart membranes can be expected. Moreover, the peculiar role of the hydrophobic organosilane TFTS CF...

Formation Mechanism Studies of Phenylene-Bridged Periodic Mesoporous Organosilicas (PMOs)

The formation of phenylene-bridged periodic mesoporous organosilicas (PMOs) in the presence of three diblock copolymers differing in hydrophobic hydrocarbon chain lengths was investigated. Hexaethylene glycol octadecylether (C(18)(EO)(6)), hexaethylene glycol hexadecylether (C(16)(EO)(6)), and hexaethylene glycol dodecylether (C(12)(EO)(6)) were chosen in order to obtain insight on the influence of the hydrocarbon chain length on the mesostructure. 1,4-Bis(triethoxysilyl)benzene (BTEB) was used as organosilica precursor under mild acidic conditions. The reactions were followed by in situ small-angle X-ray diffraction (SAXD) on-time in a capillary flow setup. It was found that during the reaction the formation of different structures was observed, which is ascribed to the hydrolysis and condensation of the organosilica precursor. In all cases, different structures evolve with time and phase transitions are observed during the measurements independent of the hydrocarbon chain length.

An unusual example of morphology controlled periodic mesoporous organosilica single crystals

Morphology and size controlled mesoporous single crystals are of special significance in various applications. In this work, ethane-included PMO single crystals with cubic and truncated-cubic morphologies have been prepared by self-assembling the surfactant and organosilica precursor in aqueous solution. The PMO single crystals are highly uniform in external morphologies and the particle sizes can be trimmed down to less than one micrometre. With the cubic pore structure, the relatively small particle sizes, and the easily-functionalized organic groups embedded in the pore walls, the PMO single crystals may find new applications in various fields.

Self-assembly of layered functionalized hybrid materials. A good opportunity for extractive chemistry

This paper is devoted to layered hybrid organic-inorganic materials obtained by self-assembly of organosilica precursors during the hydrolytic sol–gel process. The self-assembly is induced by lipophilic van der Waals interactions between alkylene chains. The introduction of functional groups such as –SS– gives rise to –SH or –SO3H functionalized materials after chemical modifications. This methodology has been extended to the formation of lamellar hybrid materials containing amino groups thanks to CO2 as bridging groups as well as the formation of lamellar hybrid materials containing carboxylic groups. In this last case, the material was elaborated thanks to in situ hydrogen bond formation between carboxylic acid groups. An easy preparation of bis-zwitterionic lamellar material from only 3-aminopropyltriethoxysilane, succinic anhydride, and ethylene diamine will be also presented. All these functional materials exhibit a very high chelating capability towards transition metal and lanthanide ions and can be used for environmental remediation.

Periodic Mesoporous Organosilica with a Hexagonally Pillared Lamellar Structure

Ordered mesoporous materials (OMMs) with well-defined pore sizes (>2 nm) and pore geometries are important in various applications that require fast mass transfer or deal with large molecules. Extensive research has resulted in the discovery of OMMs with three types of mesostructures: (i) bi- or multicontinuous, (ii) columnar, and (iii) discontinuous (cagelike). However, another type, the pillared lamellar structure, which has long been sought and has been mathematically computed and known to exist in the research fields of surfactant and multiblock-copolymer mesophases, still remains a mesostructure that has not been observed in real OMMs for any specific symmetry. Herein, we report an unprecedented type of ordered mesoporous material with a hexagonally pillared lamellar (HPL) structure (P6(3)/mmc) that can be synthesized via a phase transformation from a lamellar mesophase by hydrothermal reaction in the presence of an organosilica precursor and a high concentration of a designed Gemini surfactant (Gem(16-3-16)) that has a large g value. The present GMO-HPL, which has an unique three-dimensional periodic structure with two-dimensionally connected pore channels running between the framework layers, provides a fascinating topological link between the lamellar and columnar (2D hexagonal) mesophases. It is unique in its application potential by making possible selective 2D diffusion in different directions.

Periodic Mesoporous Organosilica Materials: Self‐Assembly of Carbamothioic Acid‐Bridged Organosilane Precursors

A new series of carbamothioic acid-containing periodic mesoporous organosilica (PMO) materials has been synthesized by a direct cocondensation method, in which an organosilica precursor N,S-bis[3-(triethoxysilyl)propyl]carbamothioic acid (MI) is treated with tetraethyl orthosilicate (TEOS), and the nonionic surfactant Pluronic 123 (P123) is used as a template under acidic conditions in the presence of inorganic additives. Moreover, the synthesis of the PMO material consisting of the MI precursor without TEOS has been realized. These novel PMO materials have large surface areas, well-ordered mesoporous structures, hollow fiberlike morphologies, and thick walls. They are also structurally well-ordered with a high organosilica precursor content, and the carbamothioic acid groups are thermally stable up to 250 degrees C. Furthermore, the organosilica materials exhibit hydrothermal stability in basic solution.

A fluorophore grafted 2D-hexagonal mesoporous organosilica: Excellent ion-exchanger for the removal of heavy metal ions from wastewater

Highly ordered 2D-hexagonal luminescent organic–inorganic hybrid mesoporous silica (LHMS-2) containing a fluorophore inside the pore walls has been synthesized hydrothermally by using a non-ionic triblock co-polymer surfactant F127 as template under strongly acidic synthesis condition. XRD and HR TEM image analyses suggest the formation of highly ordered 2D-hexagonal mesophase from a mixture of diimine organosilica and tetraethyl orthosilicate (TEOS) precursors. 13C CP MAS, 29Si MAS NMR, UV–visible absorption and PL spectroscopic data suggests the incorporation of bridging organic diimine fluorophore in the solid mesoporous material. N2 sorption data indicates high BET surface area together with type IV isotherm, characteristics of well-defined mesopores for this material. This fluorophore grafted mesoporous material shows very strong affinity for metal cations like Fe3+, Zn2+, Cd2+ and Hg2+, and thus can be very efficiently utilized for the removal of these heavy metal ions from wastewater.

Effect of Morphology and Pore Size of Sulfonated Mesoporous Benzene-silicas in the Preparation of Poly(vinyl alcohol)-Based Hybrid Nanocomposite Membranes for Direct Methanol Fuel Cell Application

Sulfonated mesoporous benzene-silicas were introduced into a poly(vinyl alcohol) (PVA) polymer matrix to act as a barrier for methanol crossover, to prepare composite electrolyte membranes for direct methanol fuel cell applications. Highly ordered 2D hexagonal mesoporous benzene-silicas were prepared using 1,4-bis(triethoxysilyl)benzene (BTEB) organosilica precursor and two kinds of organic templates, such as an octadecyltrimethylammonium bromide (ODTMA) and a Pluronic P123 poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer, to investigate the effect of the morphology and the pore size on the methanol permeability and the proton conductivity of the membranes. The sulfonated mesoporous benzene-silica and PVA were mixed with a sulfosuccinic acid (SSA) cross-linker to improve the membrane stability from mechanical and conductive viewpoints. The physical and chemical characterization of the hybrid electrolyte membranes was performed by varying the contents of sulfonated mesoporous benzene-silicas and SSA. All the hybrid membranes studied showed good performance in lowering the methanol crossover (i.e., approximately 68% reduction in comparison with the Nafion117 membrane), and mesoporous benzene-silica with smaller particle morphology and pores (2-3 nm) was observed to be a more effective additive.

Hydrophobic mesoporous materials for immobilization of enzymes

This study examined the adsorption of lysozyme using three different types of periodic mesoporous organosilicas (PMOs) produced from either bis[3-(trimethoxysilyl)propyl] amine (BTMS-amine), 1,4-bis(triethoxysilyl)benzene (BTES-benzene), or 4-bis(triethoxysilyl) biphenyl (BTES-biphenyl) as precursors. For comparison, the adsorption of lysozyme on mesoporous silica SBA-15 as an absorbent was also investigated. The mesostructure of pristine PMOs and SBA-15 were characterized by small angle X-ray scattering (SAXS), transmission electron microscopy (TEM), nitrogen adsorption/desorption isotherm curves and 29Si and 13C solid state CP MAS NMR spectroscopy. The zeta potential was measured to interpret the dispersive and adsorptive ability of the mesoporous materials. BTES-biphenyl with a more hydrophobic character showed a higher adsorption capacity at the pH near the pI of the organosilica precursor than the other two PMO’s. The maximum amount of enzyme was obtained at pH close to the pI. BTES-benzene and BTES-biphenyl showed high affinity to lysozyme and adsorbed most of the lysozymes. In addition, the adsorption rates of the hydrophobic PMOs were quite fast at pH 10.2; faster than that of SBA-15. Overall, hydrophobic PMO materials are suitable for immobilizing lysozyme at pH 10.2.

Synthesis of Large‐Pore Urea‐Bridged Periodic Mesoporous Organosilicas

In this article we report the successful synthesis of a new class of periodic mesoporous organosilicas (PMOs) with a urea-bridged organosilica precursor under acid-catalyzed and inorganic-salt-assisted conditions. The large-pore hybrid materials have an ordered mesostructure with uniform pore size distributions, excellent thick framework walls, thermal stability, and specific functional groups. The composition of the mesoporous organosilicas was characterized by FTIR spectroscopy, (13)C cross-polarization magic-angle spinning (CP MAS) NMR spectroscopy, and (29)Si MAS NMR spectroscopy.

Preparation and catalytic activity of periodic mesoporous organosilica incorporating Lewis acidic chloroindate(III) ionic liquid moieties

Preparation of novel periodic mesoporous organosilica (PMO) materials of SBA-15 incorporating Lewis acidic chloroindate(III) ionic liquid moieties was achieved via a multistep process, in which N-(3-triethoxysilylpropyl), N(3)-(3-trimethoxysilylpropyl-4,5-dihydroimidazolium chloride was firstly synthesized and used as bridging organosilica precursor to co-condense with tetraethoxysilane (TEOS) in the presence of P123, followed by removal of the template, then the addition of InCl 3 gave rise to the PMO materials with Lewis acidity. The obtained PMO materials were well characterized. The XRD, TEM, and N 2 adsorption–desorption results indicated that the PMO materials retained the structural integrity during the template extraction and successive InCl 3-loading process. FT-IR and solid-state 29Si and 13C CP/MAS-NMR analyses showed the organic structure of the bridging organosilica precursor could be incorporated into the PMO materials invariantly. Compared with SBA-15 supported InCl 3, the PMO materials revealed high efficiency and better reusability in the Friedel–Crafts reaction between benzene and benzyl chloride. More importantly, such immobilized chloroindate(III) ionic liquids had low moisture sensitivity, showing the great potential for practical applications.

Periodic Mesoporous Benzene- and Thiophene-Silicas Prepared Using Aluminum Chloride as an Acid Catalyst: Effect of Aluminum Salt/Organosilane Ratio and Stirring Time

Periodic mesoporous benzene-silica and thiophene-silica with two dimensional (2D) p6mm symmetry were synthesized in the presence of a nonionic poly(ethylene oxide)-poly(dl-lactic acid-co-glycolic acid)-poly(ethylene oxide) (PEO-PLGA-PEO) block copolymer template using aluminum chloride hexahydrate (AlCl3·6H2O) as an acid catalyst instead of the proton-containing hydrochloric acid (HCl). 1,4-Bis(triethoxysilyl)benzene (BTEB) and 2,5-bis(triethoxysilyl)thiophene (BTET) were used as organosilica precursors. The effect of the AlCl3·6H2O/organosilane ratio and the stirring time was investigated to find the optimum experimental conditions. It was shown that the highly ordered 2D hexagonal mesostructures of aromatic-silicas were formed using relatively small amounts of AlCl3 ([AlCl3·6H2O]/[BTEB] and [AlCl3·6H2O]/[BTET] ≥ 1) and a stirring time of about 20 h. The BET surface areas, pore volumes, and pore diameters of the benzene- and thiophene-silicas studied varied from 505 to 1215 m2 g−1, from 0.55 to 1.62 cm3 ...