Large-pore Periodic Mesoporous Organosilicas Research Articles

Large-Pore Periodic Mesoporous Organosilicas as Advanced Bactericide Platforms.

Despite the versatility of periodic mesoporous organosilicas (PMOs), the bactericide capacity of these hybrid platforms has seldom been explored. Herein, we describe the synthesis of large-pore phenylene-bridged PMOs, mesostructured by polyion complex (PIC) micelles (PICPMOs) incorporating an antibiotic, neomycin B. A key feature of this approach is that the bioactive molecules are directly encapsulated within the PICPMOs during their formation. The engineered PICPMOs exhibit a well-ordered hexagonal mesophase with a molecular-scale crystallinity and large mesopores (8 nm), which facilitates pH-triggered delivery of the drug. The results obtained with a pathogenic Escherichia coli strain clearly demonstrate the potential of such PICPMOs for antibacterial applications.

Face-Centered-Cubic Large-Pore Periodic Mesoporous Organosilicas with Unsaturated and Aromatic Bridging Groups

Large-pore ethenylene-bridged (-CH═CH-) and phenylene-bridged (-C(6)H(4)-) periodic mesoporous organosilicas (PMOs) with face-centered-cubic structure (Fm3m symmetry) of spherical mesopores were synthesized at 7 °C at low acid concentration (0.1 M HCl) using Pluronic F127 triblock copolymer surfactant in the presence of aromatic swelling agents (1,3,5-trimethylbenzene, xylenes-isomer mixture, and toluene). In particular, this work reports an unprecedented block-copolymer-templated well-ordered ethenylene-bridged PMO with cubic structure of spherical mesopores and an unprecedented block-copolymer-templated face-centered cubic phenylene-bridged PMO, which also has an exceptionally large unit-cell size and pore diameter. The unit-cell parameters of 30 and 25 nm and the mesopore diameters of 14 and 11 nm (nominal BJH-KJS pore diameters of 12-13 and 9 nm) were obtained for ethenylene-bridged and phenylene-bridged PMOs, respectively. Under the considered reaction conditions, the unit-cell parameters and pore diameters were found to be similar when the three different methyl-substituted benzene swelling agents were employed, although the degree of structural ordering appeared to improve for phenylene-bridged PMOs in the sequence of decreased number of methyl groups on the benzene ring.

Synthesis of uniform periodic mesoporous organosilica hollow spheres with large-pore size and efficient encapsulation capacity for toluene and the large biomolecule bovine serum albumin

Large-pore periodic mesoporous organosilica (PMO) hollow spheres with controllable pore size and high pore volume (2.5 cm 3 g −1) were successfully synthesized at low-temperature (∼15 °C) by using the triblock copolymer Pluronic F127 as a template and 1,3,5-trimethylbenzene (TMB) as a swelling agent in the presence of inorganic salt (KCl). Transmission electron microscopy (TEM) measurements show that the PMO hollow spheres are uniform and well dispersed, and the composites have a large wall thickness. The influence of TMB, KCl, CTAB contents and media acidity on the mesostructure was systematically studied. The pore size (9.8–15.1 nm) of the hollow spheres can be gradually expanded by increasing TMB content together with a relatively high acidity. By controlling the content of CTAB, successive structural transformation from hollow sphere to wormlike mesostructure and eventually to ordered body-centered cubic (space group of Im-3m) mesostructure is observed. Our results reveal that the hydrophobicity of bis(triethoxysilyl)ethane (BTSE) and low-temperature approach contribute to the slow hydrolysis rate of silica precursors, which leads to weak interaction between individual TMB/F127 micelles and silicate oligomers. Furthermore, the salting-out effect of KCl may influence the swelling capacity of individual micelles as well as decrease the critical micelle concentration and critical micelle temperature, resulting in the formation of PMO hollow spheres from the assembly of individual TMB/F127 micelles with silicate oligomers. The composites exhibit efficient adsorption capacity (703 mg g −1) for toluene, suggesting they are a potentially useful adsorbent for removal of volatile organic compounds. The PMO hollow spheres allow biomolecules with large molecular weight to diffuse in, and show superior encapsulation capacity of bovine serum albumin (BSA) molecules (∼585 mg g −1) over other porous materials.

A General Strategy for the Rational Design of Size‐Selective Mesoporous Catalysts

A series of functionalized mesoporous silicas with cagelike pore topology has been synthesized and screened for size-selective catalytic transformations. The aluminum-catalyzed Meerwein-Ponndorf-Verley (MPV) reduction of differently sized aromatic aldehydes (benzaldehyde and 1-pyrenecarbox-aldehyde) has been investigated as a test reaction. The catalysts were synthesized in a two-step grafting sequence comprising pore-size engineering of mesoporous silicas (SBA-1, SBA-2, SBA-16) with long-chain alkyl dimethylaminosilanes and surface organoaluminum chemistry with triethylaluminum [{Al(CH(2)CH(3))3}2]. Size-selective reaction behavior was found for small pore SBA-1 materials, and the selectivity could be efficiently tuned by selecting a silylating reagent of appropriate size. The results are compared with the catalytic performance of a large-pore periodic mesoporous organosilica PMO[SBA-1] and the nonporous high-surface-area silicas Aerosil 300/380.

Synthesis of Highly Ordered Large-Pore Periodic Mesoporous Organosilica Rods

Highly ordered rods of large-pore periodic mesoporous organosilica (PMO) were successfully synthesized at low acid concentrations and in the presence of inorganic salt using triblock copolymer P123 as template. The roles of inorganic salt, acidity and temperature in the production of highly ordered mesostructure and the morphology control of PMOs were examined and elucidated. It was found that the addition of inorganic salt can dramatically widen the range of the synthesis parameters to produce highly ordered 2D hexagonal pore structure of p6mm symmetry. However, the uniform rods of PMOs can only be synthesized in a narrow range of acid and salt concentrations, which was sensitive to induction time. The results also showed that the optimized salt concentration (1 M) and low acidity (0.167 M) at 40 oC were beneficial to not only the production of highly ordered mesostucture but also the control of rod-like morphology. Highly ordered rods can also be produced at low temperature (35 oC) with high salt amount (1.5 M) or high temperature (45 oC) with low salt concentration (0.5 M).

Synthesis and lysozyme adsorption of rod-like large-pore periodic mesoporous organosilica

Highly ordered rod-like large-pore periodic mesoporous organosilica (PMO) was successfully synthesized at low acid concentration with the assistance of inorganic salt using triblock copolymer P123 as a template. The roles of inorganic salt and acidity in the production of highly ordered mesostructure and the morphology control of PMOs were investigated. It was found that the inorganic salt can significantly widen the range of the synthesis parameters to produce highly ordered 2D hexagonal pore structure of p6mm symmetry. However, the uniform rod-like PMOs can only be synthesized in a narrow range of acid and salt concentrations, which were sensitive to induction time. The adsorption of lysozyme on PMO was studied at different pH values in comparison with adsorption on pure silica material under controlled morphology and pore structure. It was found that the adsorption capacity of lysozyme on the PMO was lower than that on pure SBA-15 silica material and the adsorption amounts are larger at pH 9.6 than at 7.0 for both materials. The results show that the electrostatic interaction between lysozyme and PMO/SBA-15 surface is more dominant than the hydrophobic forces and the interaction of neighboring lysozyme molecules also plays an important role.

Control of ordered structure and morphology of large-pore periodic mesoporous organosilicas by inorganic salt

Highly ordered rodlike periodic mesoporous organosilicas (PMO) were successfully synthesized using 1,2-bis(trimethoxysilyl)ethane as an precursor and triblock copolymer P123 as a template at low acid concentration and in the presence of inorganic salts (KCl). The role of acid and salt as well as the effects of synthesis temperature and reactant mole ratio in the control of morphology and the formation of ordered mesostructure was systematically examined. It was found that the addition of inorganic salt can dramatically expand the range of the synthesis parameters to produce highly ordered PMO structure and improve the quality of PMO materials. The morphology of PMOs was significantly dependent on the induction time for precipitation. The uniform PMO rods can only be synthesized in a narrow range of acid and salt concentrations. The results also show that the optimized salt concentration (1 M) and low acidity (0.167 M) were beneficial to the formation of not only highly ordered mesostructure but also rodlike morphology. Increasing acidity resulted in fast hydrolysis reaction and short rod or plate-like particles. Highly ordered rod can also be prepared at low temperature (35 °C) with high salt amount (1.5 M) or high temperature (45 °C) with low salt amount (0.5 M). Optimum reactant molar composition at 40 °C is 0.035P123:8KCl:1.34HCl:444H 2O:1.0bis(trimethoxysilyl)ethane. Lower or higher SiO 2/P123 ratio led to the formation of uniform meso-macropores or pore-blocking effect.

Synthesis and Bio-adsorptive Properties of Large-Pore Periodic Mesoporous Organosilica Rods

Highly ordered large-pore periodic mesoporous organosilica (PMO) with a rodlike morphology was successfully synthesized at low acid concentrations and in the presence of inorganic salt using triblock copolymer P123 as a template. The inorganic salt can not only promote the formation of highly ordered mesoporous structure but also control the morphology of PMO materials. The adsorption of bovine heart cytochrome c (cyt c) on PMO was studied at different ionic strengths and pHs by comparing with the adsorption on pure silica materials with similar morphology and pore structure. The results show that the adsorbed amount reaches the maximum around the isoelectric point of cyt c and the PMO materials do not have higher adsorbed capacity than SBA-15 silica. The specific adsorption amounts of cyt c on PMO or pure silica decrease as ionic strengths increase at all pH conditions. Our results directly support the conclusion that the electrostatic interaction between cyt c and PMO/pure silica surface is more dominan...

Morphologies of Large-Pore Periodic Mesoporous Organosilicas

In this article, we report a systematic investigation on the morphologies of SBA-15 type large-pore periodic mesoporous organosilicas templated by the block copolymer P123. By tuning synthetic parameters such as stirring, acidity, reaction ratio, reaction duration, and autoclaving, a wide spectrum of unique primary particle morphologies, such as the spindle-, pearl-, diamond-, rod-, and platelike particles, and nanoparticles has been prepared. These primary particles were found to self-assemble in solution to form various large hierarchical macrostructures, such as mesostructured necklaces and cobweb-supported necklaces. The assembling process was elucidated with the information observed at different stages of reaction. Stirring, reaction duration, and autoclaving were identified to be the key factors affecting the efficiency and degree of the self-assembly process. A nucleation-accretion mechanism for the formation of various PMO primary particles was proposed by examining the relation between the external morphologies and the underlying mesostructure.

Synthesis of Large-Pore Periodic Mesoporous Organosilica (PMO) with Bicontinuous Cubic Structure of Ia–3d Symmetry

Abstract Ordered three-dimensional (3-D) bicontinuous cubic Ia–3d-type periodic mesoporous organosilica (PMO) with large pore size ( >6 nm) has been synthesized by using triblock copolymer P123 as a template and 1,2-bis(triethoxysilyl)ethane as an organically bridged silica source.

Pore structure characterization of large-pore periodic mesoporous organosilicas synthesized with varying SiO2/template ratios

Periodic mesoporous organosilicas (PMOs) synthesized by hydrolysis and condensation of bridged silsesquioxanes (RO) 3 Si-R′-Si(OR) 3 in the presence of surfactant template are an emerging family of novel functional materials. In this study, the synthesis of ethylene-bridged PMOs with a highly ordered pore structure was demonstrated by using a nonionic surfactant P123 as a template under acidic conditions. Emphasis was made at the influence of SiO 2 /P123 ratios on the structural properties such as type of pore structure, the presence or absence of micropores and macropores, and pore volume. It was observed that an increase in SiO 2 /P123 ratios led to a gradual increase in the microporous volume. In the mean time, a structural transition from an open-channel pore structure to a cage-like pore structure was observed as the SiO 2 /P123 ratios were increased.

Pore structure characterization of large-pore periodic mesoporous organosilicas synthesized with varying SiO2/template ratios

Periodic mesoporous organosilicas (PMOs) synthesized by hydrolysis and condensation of bridged silsesquioxanes (RO)3Si-R′-Si(OR)3 in the presence of surfactant template are an emerging family of novel functional materials. In this study, the synthesis of ethylene-bridged PMOs with a highly ordered pore structure was demonstrated by using a nonionic surfactant P123 as a template under acidic conditions. Emphasis was made at the influence of SiO2/P123 ratios on the structural properties such as type of pore structure, the presence or absence of micropores and macropores, and pore volume. It was observed that an increase in SiO2/P123 ratios led to a gradual increase in the microporous volume. In the mean time, a structural transition from an open-channel pore structure to a cage-like pore structure was observed as the SiO2/P123 ratios were increased.

A Novel Route toward the Synthesis of High-Quality Large-Pore Periodic Mesoporous Organosilicas

In this paper, we report a novel route to the synthesis of high-quality, large-pore periodic mesoporous organosilicas (PMOs) using triblock copolymer P123 as a template. The novelty lies in that highly ordered PMOs can only be synthesized at a limited range of low acid concentrations, which differs from traditional approach to the synthesis of similar materials including large-pore periodic mesoporous silicas (PMSs). The role that acid plays in the synthesis of high-quality PMOs and PMSs was critically examined, compared, and interpreted.

Triblock Copolymer Synthesis of Highly Ordered Large-Pore Periodic Mesoporous Organosilicas with the Aid of Inorganic Salts

This communication describes the first preparation of highly ordered large-pore hexagonal periodic mesoporous organosilicas (PMOs) using triblock copolymer P123 as the template and inorganic salts as the auxiliary agents under strongly acidic conditions. The long-range structural order of the PMOs results from the enhanced self-assembly interaction imparted by inorganic salts.

Highly ordered three-dimensional large-pore periodic mesoporous organosilica with Im3m symmetry.

Highly ordered three-dimensional Im3m-type periodic mesoporous organosilica with a cavity size of 9.8 nm has been synthesized under strongly acidic media in the presence of inorganic salts using triblock copolymer F127 as the template and 1,2-bis(trimethoxysilyl)ethane as the organically bridged silica source.

Nonionic oligomeric polymer directed synthesis of highly ordered large pore periodic mesoporous organosilica

Highly ordered large-pore organosilica with 2D hexagonal structure has been prepared reproducibly in high yield using nonionic oligomeric Brij 76 as the structure-directing agent at 50 °C.

Synthesis of Periodic Mesoporous Organosilicas with Block Copolymer Templates

Large pore periodic mesoporous organosilicas have been synthesized using a triblock copolymer template. Organosilicas with pore sizes ranging from 6−20 nm have been prepared under acidic conditions.