Organosilica Monolith Research Articles

Characterization of hybrid organo-silica monoliths for possible application in the gradient elution of peptides.

We characterized thermally polymerized organo-silica hybrid monolithic capillaries to test their applicability in the gradient elution of peptides. We have used a single-pot approach utilizing 3-(methacryloyloxy)propyltrimethoxysilane (MPTMS), ethylene dimethacrylate (EDMA), and n-octadecyl methacrylate (ODM) as functional monomers. The organo-silica monolith containing MPTMS and EDMA was compared with the stationary phase prepared by adding ODM to the original polymerization mixture. Column prepared using a three-monomer system provided a lower accessible volume of flow-through pores, a higher proportion of mesopores, and higher efficiency. We utilized isocratic and gradient elution data to predict peak widths in gradient elution. Both protocols provided comparable results and can be used for peptide peak width prediction. However, applying gradient elution data for peak width prediction seems simpler. Finally, we tested the effect of gradient time on achievable peak capacity in the gradient elution of peptides with a column prepared with a three-monomer system providing a higher peak capacity. However, the performance of hybrid organo-silica monolithic stationary phases in gradient elution of peptides must be improved compared to other monolithic stationary phases. The limiting factor is column efficiency in highly aqueous mobile phases, which needs to be focused on.

Supporting non-noble metal composite organosilica monolithic foam for efficiently catalytic degradation of aromatic compounds

The porous monolithic materials supporting non-noble metal nanoparticles that acted as catalysts have recently gained increasing attention due to their robust activity and regenerative ability, resulting in simple chemical progress. It is crucial for the catalytic performance that the monolithic supporters have a hierarchically porous structure while the non-noble metal nanoparticles show a good control of their dimensions and oxidation states. Herein this work reports the composite organosilica monolithic (OSM) foams containing non-noble metal like Cu-, Co-, or Ni-based nanoparticles. As-prepared the supporting non-noble metal nanoparticles organosilica monolithic foams could act as monolithic catalyst, showing the efficiently catalytic performance for the degradation of aromatic compounds. These monolithic catalysts were prepared via amino-functionalization of organosilica monolith with ethylenic groups, followed by supporting non-noble metal nanoparticles through a simple reduction process. The monolithic catalyst involved Cu-based nanoparticles (Cu/OSM) were obtained via reduction of Cu 2+ using a mixture of NaBH 4 with and without the aid of polyvinylpyrrolidone K 90 (PVP), as denoted by Cu/OSM-N and Cu/OSM-P, respectively. It was demonstrated that the addition of PVP into the system caused the higher Cu content, the better distribution of the smaller Cu-based nanoparticles and a richer Cu(0) nanoparticles. Furthermore Cu/OSM-P exhibited high stability and durable activity, with approximately 95% conversion within 14 successive cycles, for the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with excess NaBH 4 in an aqueous solution. This catalyst also showed a remarkable catalytic performance for the degradation of other organic aromatic dyes like methylene blue (MB), methyl orange (MO), rhodamine B (RhB) and even their mixture. In addition, Co/OSM-P and Ni/OSM-P fabricated with the same method also showed high catalytic performance for reduction of 4-NP. We believe that the strategy developed in this work is very useful for the simple, low-cost, and environmentally friendly preparation of porous composite monolithic catalysts containing non-noble metal nanoparticles.

Robust porous organosilica monoliths via a surfactant-free high internal phase emulsion process for efficient oil-water separation

Elastic porous organosilica monoliths (POMs) are successfully prepared by water in oil (w/o) high internal phase emulsions (HIPEs) with a novel silica precursor named polyethoxysiloxane (PEOS) as sole stabilizer. The stability of the HIPEs and the mechanical strength of the POMs are investigated as functions of PEOS and crosslinker contents in the oil phase. FESEM reveals that PEOS molecules play a significant role of in-situ growth into silica particles to strengthen the POMs, which enables the successful preparation of elastic POMs. Furthermore, oil-water separation behavior of the POMs is studied. Both the absorbent capacity and speed are considerably superior to the previously reported PDMS sponges.

Mercapto-Functionalized Porous Organosilica Monoliths Loaded with Gold Nanoparticles for Catalytic Application.

Porous organosilica monoliths have attracted much attention from both the academic and industrial fields due to their porous structure; excellent mechanical property and easily functionalized surface. A new mercapto-functionalized silicone monolith from a precursor mixture containing methyltrimethoxysilane; 3-mercaptopropyltrimethoxysilane; and 3-mercaptopropyl(dimethoxy)methylsilane prepared via a two-step acid/base hydrolysis–polycondensation process was reported. Silane precursor ratios and surfactant type were varied to control the networks of porous monolithic gels. Gold nanoparticles were loaded onto the surface of the porous organosilica monolith (POM). Versatile characterization techniques were utilized to investigate the properties of the synthesized materials with and without gold nanoparticles. Scanning electron microscopy was used to investigate the morphology of the as-synthesized porous monolith materials. Fourier transform infrared spectroscopy was applied to confirm the surface chemistry. 29Si nuclear magnetic resonance was used to investigate the hydrolysis and polycondensation of organosilane precursors. Transmission electron microscopy was carried out to prove the existence of well-dispersed gold nanoparticles on the porous materials. Ultraviolet–visible spectroscopy was utilized to evaluate the high catalytic performance of the as-synthesized Au/POM particles

Preparation of low density organosilica monoliths containing hollow silica nanospheres as thermal insulation materials

In this study, we demonstrated that low density organosilica monoliths (LDM) containing hollow silica nanospheres (HSNS) may have a great potential for the use as thermal insulation materials. First, hydrophilic and hydrophobic HSNS have been prepared by a simple sol-gel method and have an average diameter centered around 120 nm and a shell thickness between 10 and 15 nm. LDM containing HSNS have then been prepared as solid cylindric materials without cracks and with a low bulk density of about 0.17 g/cm3. LDM containing hydrophobic HSNS have shown a measured thermal conductivity of about 0.031 W/(mK), compared to 0.045 W/(mK) of the corresponding LDM without HSNS.

Macro-mesoporous organosilica monoliths with bridged-ethylene and terminal-vinyl: High-density click functionalization for chromatographic separation

A novel kind of macro-mesoporous organosilica monolith, with not only bridged-ethylene groups incorporated into the skeleton but also terminal-vinyl groups protruded from the pore-wall, was prepared so that high-loaded double bonds were achieved. Via highly efficient “thiol-ene” click reaction of such high-loaded double bonds, the surface coverage of C18 groups on monolith could be 5.54 μmol m−2, significantly larger than that of the reported separation materials, beneficial to improvement of separation resolution, especially for peptide separation. The separation performance was evaluated using alkylbenzenes and standard peptides. Furthermore, the tryptic digests of complex sample was successfully analyzed. Because of high separation resolution of our prepared hybrid monolith, the peak capacity for 6-h gradient was achieved as 482. Coupling to LTQ Orbitrap Velos Mass Spectrometry, 22523 tryptic peptides from 4423 proteins were identified from the HeLa cells, more than that using the other long-gradient separation by the same system reported, showing great promising of such monolith for large-scale in-depth proteomic analysis.

One-step preparation of emulsion-templated amino-functionalized porous organosilica monoliths for highly efficient Cr(VI) removal

In this study, we reported that the amino-functionalized organosilica monoliths (amino-OSMs) without need post-synthesis functionalization were prepared in one-step emulsion-templated method. Herein, formation of organosilica skeleton and amino-functionalization of skeleton surface can be simultaneously realized by addition of ammonia. The SEM images showed that the amino-OSMs had a rich pore structures with high adjustability via the simple change in formulation of the emulsions. The successful graft of amino groups on the surface of the organosilica monolith was confirmed by EDS and XPS measurements. The amino-OSMs prepared in this work show the excellent Cr(VI)-removal capacity from the aqueous solution. It is demonstrated that Cr(VI) adsorption on amino-OSM-3 was best described by Langmuir models and pseudo-second-order kinetic. The adsorption efficiency of amino-OSM-3 for Cr(VI) was measured to be 92.8% at room temperature, still remained as high as 85.1% after five recycles as indicative of the good durability. Furthermore, the treated capacity of amino-OSM-3 is 4.25 kg·g−1 with initial concentration of 200 μg·L−1 through the column with a height of 0.5 cm. Correspondingly, Cr(VI) aqueous solution after treatment meet the requirement of the World Health Organization water discharge standard with Cr(VI) concentration as low as 50 μg·L−1. This work paves the way for the scale-up production of amino-OSMs using emulsion-templated technique for potential application in heavy metal removal.

Clickable Periodic Mesoporous Organosilica Monolith for Highly Efficient Capillary Chromatographic Separation.

A novel clickable periodic mesoporous organosilica monolith with the surface area up to 1707 m(2) g(-1) was in situ synthesized in the capillary by the one-step condensation of the organobridged-bonded alkoxysilane precursor bis(triethoxysilyl)ethylene. With Si-C bonds in the skeleton, the monolith possesses excellent chemical and mechanical stability. With vinyl groups highly loaded and homogeneously distributed throughout the structure, the monolith can be readily functionalized with functional groups by effective thiol-ene "click" chemistry reaction. Herein, with "click" modification of C18, the obtained monolith was successfully applied for capillary liquid chromatographic separation of small molecules and proteins. The column efficiency could reach 148,000 N/m, higher than most reported hybrid monoliths. Moreover, intact proteins could be separated well with good reproducibility, even after the monolithic column was exposed by basic mobile phase (pH 10.0) overnight, demonstrating the great promising of such monolith for capillary chromatographic separation.

Photopolymerized organo‐silica hybrid monolithic columns: Characterization of their performance in capillary liquid chromatography

Porous hybrid organo-silica monoliths have been prepared inside pretreated 100 μm id UV transparent fused-silica capillaries using simultaneous sol-gel transition and polymerization of 3-(methacryloyloxy)propyl trimethoxysilane in the presence of toluene as a porogen. The sol-gel reaction was catalyzed by hydrochloric acid while various photoinitiators including azobisisobutyronitrile, 2,2-dimethoxy-2-phenylacetophenone, and Irgacure 819 were used for the photopolymerization carried out under irradiation with UV light at a wavelength of 254 or 365 nm. The chromatographic performance of photopolymerized monolithic columns in RP liquid chromatographic mode was assessed with respect to the following metrics: column efficiency, methylene and steric selectivity, effect of silanol groups, van Deemter plot, permeability, and pore size distribution. Columns with an efficiency of up to 77 000 plates/m for benzene has been achieved at a flow velocity of 0.47 mm/s. The performance of photopolymerized hybrid monolithic column was compared to the performance of columns prepared via thermally initiated polymerization.

Sol−Gel Processing of a Glycolated Cyclic Organosilane and Its Pyrolysis to Silicon Oxycarbide Monoliths with Multiscale Porosity and Large Surface Areas

This study is related to the preparation of silicon oxycarbide monoliths comprising a hierarchical network build-up from the pyrolysis of monolithic organosilica gels. A novel glycol-modified 1,3,5-trisilacyclohexane-carbosilane “[Si(OCH2CH2OH)2CH2]3” was processed via a polymerization-induced phase separation process in hydrochloric acid solution containing the Pluronic P123 block copolymer and potassium chloride. Highly porous organosilica monoliths with interconnected macropores and a large amount of uniformly sized polymer-templated mesopores within the macroscopic framework domains were obtained after supercritical fluid extraction. The monoliths were pyrolyzed in argon atmosphere at 1000 °C to yield silicon oxycarbide monoliths by maintaining the hierarchical porosity of the organosilica gel. Both the organosilica gels and the silicon oxycarbide monoliths were thoroughly investigated with standard characterization techniques. If no salt was used for the preparation of organosilica gels, no distinct ...

Organosilica Monoliths with Multiscale Porosity: Detailed Investigation of the Influence of the Surfactant on Structure Formation

Monolithic inorganic-organic hybrid materials have been synthesized via sol-gel processing of an ethylene glycol-modified ethane-bridged silane precursor in aqueous solution of the non-ionic block copolymer Pluronic™ P123. The influence of different sol compositions on the final gel structure was investigated in detail. The resulting materials consist of macroporous networks comprising periodically arranged mesopores, where the macropore size as well as the morphology of the material can be deliberately tailored by reducing the amount of the block copolymer template. The structure was investigated by small-angle X-ray scattering as well as scanning and transmission electron microscopy. Information on the porosity, surface area and pore size distribution were obtained from BET/BJH analysis and mercury intrusion measurements. For a more detailed insight into mechanism and kinetics of the mesostructure formation, in-situ SAXS experiments were carried out.

High-quality, oriented and mesostructured organosilica monolith as a potential UV sensor

We synthesized high-quality and oriented periodic mesoporous organosilica (PMO) monoliths through a solvent evaporation process using a wide range of mole ratios of the components: 0.17–0.56 1,2-bis(triethoxysilyl)ethane (BTSE): 0.2 cetyltrimethylammonium chloride (CTACl): 0–1.8 × 10 −3 HCl: 0–80 EtOH: 5–400 H 2O. X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) images indicated that the mesoporous channels within the monolith samples were oriented parallel to the flat external surface of the PMO monolith and possessed a hexagonal symmetry lattice ( p6 mm). The PMO monolith synthesized from a reactant composition of 0.35 BTSE: 0.2 CTACl: 1.8 × 10 −6 HCl: 10 EtOH: 10 H 2O had a pore diameter, pore volume, and surface area – obtained from an N 2 sorption isotherm – of 25.0 Å, 0.96 cm 3 g −1 and 1231 m 2 g −1, respectively. After calcination at 280 °C for 2 h in N 2 flow, the PMO monolith retained monolith-shape and mesostructure. Pore diameter and surface area of the calcined PMO monolith sample were 19.8 Å, 0.53 cm 3 g −1 and 1368 m 2 g −1, respectively. We performed 29Si and 13C CP MAS NMR spectroscopy experiments to confirm the presence of Si–C bonding within the framework of the PMO monoliths. We investigated the thermal stability of the PMO monoliths through thermogravimetric analysis (TGA). In addition, rare-earth ions (Eu 3+, Tb 3+ and Tm 3+) were doped into the monoliths. Optical properties of those Eu 3+, Tb 3+ and Tm 3+-doped PMO monoliths were investigated by photoluminescence (PL) spectra to evaluate their potential applicability as UV sensors.