Mesoporous Benzene-silica Research Articles

Highly stable mesoporous Ni-phyllosilicate particle under high temperature hydrothermal and base conditions towards industrial catalytic applications

Two mesoporous nickel phyllosilicate (Ni-PS) samples with Ni/Si ratios of 0.3 and 1 were used to compare high-temperature hydrothermal stability. The Ni-PS structures have well-developed porosity and pore size distributions mainly ranging from 2 to 20 nm. To assess their hydrothermal resistance as a reusable heterogeneous catalyst in high-temperature reactions, the samples were exposed to 800 °C for 7 days using steam-supplied muffle furnaces. Three types of mesoporous silica samples (i.e. MCM-41, SBA-15, and mesoporous benzene-silica) and two zeolites (i.e. ZSM-5 and zeolite-Y) were compared under the same conditions. The hydrothermal resistance was primarily confirmed based on changes in pore size distribution and surface area through nitrogen-sorption isotherm analysis. The crystal structure and the binding energy of each sample were investigated by X-ray diffraction and X-ray photoelectron spectroscopy measurements. The Ni-PS structures displayed excellent stability (i.e. BET surface area retained over 77 % and 65 % after 1-d and 7-d treatment, respectively.) compared with other mesoporous samples, and even higher stability than zeolite Y. In addition, structural stability at pH = 10 is much higher than that of ZSM-5. This suggests that it could be used for various catalytic chemical reactions including hydrogenation and cracking processes because NiO and Ni nanoparticles are uniformly distributed on the surface, maintaining their particle shape even after a reduction process.

Multifunctional periodic mesoporous benzene-silicas for evaluation of CO2 adsorption at standard temperature and pressure

Abstract Bi-functional periodic mesoporous organosilicas (PMOs) embedded with phenylene- and isocyanurate-bridging groups have been synthesized by a one-pot co-condensation method using 1,4-bis(triethoxysilyl)benzene and tris[3-(trimethoxysilyl)propyl]isocyanurate precursors in the presence of a poly(ethylene oxide)-poly( dl -lactic acid-co-glycolic acid)-poly(ethylene oxide) (PEO-PLGA-PEO) triblock copolymer named LGE54 under acidic conditions. Block copolymer template has been removed by solvent-extraction to get the template-free PMO whereas PLGA block chains from the copolymer template were also removed selectively by thermal treatment at 250 °C retaining PEO chains inside the silica framework. Furthermore, the bi-functional PMO and tri-functional PEO containing PMOs were modified with N-[3-(trimethoxysilyl)propyl]ethylenediamine to prepare amine-coated PMOs on the pore surface. The bi-, tri-, and tetra-functional PMO samples have been thoroughly characterized using small angle X-ray scattering (SAXS) and nitrogen adsorption isotherms to resolve the presence of ordered mesostructure and surface area of the PMOs. Also, solid-state 13C- and 29Si CP-MAS NMR studies have been performed to investigate significant chemical linkages from amine-containing modifiers and poly(ethylene oxide) group inside and on the surface of PMO samples. Scanning electron microscopic (SEM), elemental analysis, and thermogravimetric analysis (TGA) have been carried out to obtain the morphology, elemental percentage and thermal stability of the multi-functional PMO samples, respectively. CO2 capture has been investigated on multi-functional PMO samples at 25 °C and 1 atm using a mixed flow by 3:2 vol ratio of CO2 and N2 gas. Amine-functionalized PMO has shown significantly higher amount of CO2 uptake than those obtained using PMO itself and the respective PMOs modified with different functionalities.

Tuning the acid content of propylsulfonic acid-functionalized mesoporous benzene-silica by microwave-assisted synthesis

Propylsulfonic-acid functionalized mesoporous phenylene-silicas have potential use in catalysis and applications demanding protonic conduction such as fuel cells. Their synthesis by conventional co-condensation is time consuming and with poor control of the incorporation of sulfonic acid. Here we report a fast, microwave-assisted synthetic route to prepare these materials with controlled acid load and structural order. It is found that the microwave energy strongly improves the kinetics of the various steps of the process, including the self-assembly of precursors (stirring), consolidation of the framework (hydrothermal treatment), surfactant extraction and the oxidation of the thiol to the sulfonic acid group. The concentration of incorporated acid groups increases linearly with the self-assembly time under microwave radiation, enabling the largest improvement of all synthetic steps. However, the mesopore order decreases significantly for microwave-assisted self-assemblies in excess of 6 h, and for microwave-assisted hydrothermal treatments longer than 3 h. The multivariate analysis of kinetic data is presented and used to derive kinetic parameters enabling the prediction of the acid load and the structural order of the materials as a function of the synthesis time under microwave radiation. For similar acid contents, full microwave synthesis is completed within 12 h, whereas nearly 84 h are needed with conventional heating sources. The protonic conductivity increases linearly with increasing acid load regardless of the used combination of synthetic steps, including MW or not. This is seen as a confirmation that the distribution of the acid groups in the pore surface is not affected by MW.

Synthesis and properties of cross-linked poly(arylene ether ketone) electrolyte membranes containing hygroscopic proton conductors

Sulfonated poly(arylene ether ketone) (SPAEK) fuel cell membranes were prepared in a cross-linked structure to enhance their dimensional and mechanical stability. Sulfonated mesoporous benzene-silica (SMBS) hygroscopic conductors were embedded in the membranes to lessen their dehydration in the low humid environment. Synthesis of the cross-linked SPAEK (CSPAEK) and its precursor was confirmed using 1H NMR spectroscopy and FT-IR spectroscopy. The effects of sulfonation degree (SD) and hygroscopic conductors on the membranes properties such as proton conductivity, methanol crossover, and thermal and mechanical stability were analyzed. The prepared CSPAEK membranes were thermally stable up to 250 °C without any chemical degradation. While the CSPAEK membranes containing hygroscopic proton conductors exhibited superior conductivity to that of Nafion®117, those with a sulfonation percent of less than 20% showed lower methanol permeability. Although the water uptake of the composite membranes was higher than that of the pristine membranes, no mechanical failure was observed.

Evaluation of different bridged organosilicas as efficient adsorbents for the herbicide S-metolachlor

The adsorption ofS-metolachlor on (organo)silicas largely depends on their composition and textural properties. Periodic mesoporous benzenesilica was particularly efficient for repetitive adsorption cycles.

Periodic Mesoporous Organosilicas as adsorbents for the organic pollutants removal in aqueous phase

Heavy organic pollutants such as pesticides and pharmaceuticals are found in wastewater and are difficult to remove by microporous adsorbents because of their large size. Mesoporous organosilicas as potential adsorbents for removal of heavy organic pollutants from aqueous phase are investigated. Propylsulfonic acid-functionalized mesoporous silica (SBA-15-SO3H) and propylsulfonic acid-functionalized periodic mesoporous benzene-silica (Ph-PMO-SO3H) are prepared by co-condensation method. Textural and structural characterizations are conducted by X-ray diffraction, N2 physisorption, solid state NMR spectroscopy, elemental analysis and confirmed the structural integrity of the materials. Material adsorption behaviors are studied in pesticide, mesosulfuron methyl (MM), removal from aqueous phase. For all the materials, adsorption kinetics are well described by a pseudo-second order model indicating the chemisorption of the MM molecules via acid–basic interaction of the neutral form. Sorption isotherms are S-shape isotherms and can be well fitted by the Freundlich model. Ph-PMO-SO3H exhibits higher sorption rate (8.95mgg−1h−1) and better sorption capacity (9.70mgg−1) than the mesoporous silica SBA-15-SO3H (4.16mgg−1h−1, 9.4mgg−1). Furthermore, Ph-PMO-SO3H has also the best MM abatement rates in aqueous phase up to 95% for initial concentrations ranging from 4 to 10ppm than microporous acidic zeolite (HFAU) (∼70%) and mesoporous silica SBA-15-SO3H (∼70%). The phenyl groups in sulfonic PMO material seem to enhance organic pollutant adsorption capacity either by reducing wall hydrophilicity or by favoring the interaction with MM phenyl rings.

Sulfonated mesoporous benzene-silica-embedded sulfonated poly(ether ether ketone) membranes for enhanced proton conduction and anti-dehydration

In polymer electrolyte fuel cell operation, a decrease in the proton conductivity of the membrane at reduced humidity is a main cause for poor cell performance at high temperature. To alleviate the dehydration of the membrane at high temperature, sulfonated mesoporous benzene-silica (sMBS) particles are embedded in sulfonated poly(ether ether ketone) (sPEEK) membranes. As the sMBS itself is highly sulfonated on both organic and inorganic moieties, the proton conductivity of composite membranes is much higher than that of the pristine sPEEK membrane, and it reaches that of Nafion 117 at a high relative humidity (RH) of 90%. The dehydration rate of the membrane is reduced significantly by the capillary condensation effect of sMBS particles with the nanometer-scale 2-D hexagonal cylindrical pores, and the proton conductivity of the composite membranes, 0.234 × 10−1 S cm−1, is much higher than that of pristine sPEEK membrane, 0.59 × 10−3 S cm−1, at a relatively low humidity of 40% RH. This maintenance of high conductivity at low humidity is attributed to the high water-holding capacity of the sMBS proton conductors. The sMBS-embedded sPEEK composite membranes show a much lower methanol permeability of 2–5 × 10−7 cm2 s−1 compared to that of Nafion 117, which is 1.6 × 10−6 cm2 s−1 at room temperature.

Role of acidity and hydrophobicity in the remarkable catalytic activity in water of sulfonic acid-functionalized phenyl-PMO materials

Periodic mesoporous benzene-silica (Ph-PMO) are interesting materials for catalytic applications due to their high surface area, meso- and molecular-scale order, high organic content in the wall and alternated hydrophobic-hydrophilic behavior. Then, propylsulfonic acid-functionalized Ph-PMO material (Ph-PMO-PrSO3H) is a very active acid solid for catalyzing aqueous organic reaction. Acid strength and hydrophobic properties are usually suggested to explain the distinct behavior of Ph-PMO-PrSO3H compared to the less active propylsulfonic acid-functionalized periodic mesoporous silica catalysts (PMS-PrSO3H). Here we present a systematic study in which, the catalytic performances in the reaction of indole with benzaldehyde of propylsulfonic acid-functionalized SBA-15 (SBA-15-PrSO3H) and Ph-PMO-PrSO3H are compared. The causes of the different activities are investigated. The strength of the Brønsted acidity of the sulfonic acid groups SO3H are characterized by adsorption of 2,6-dimethylpyridine (DMP) monitored by FTIR spectroscopy. The hydrophobic index (HI) of each solid is determined by water/toluene competitive adsorption. The calculation of the turnover frequencies (TOFs) enables to show that, among all the samples studied, Ph-PMO-PrSO3H exhibit the higher catalytic activity. The TOF depends on the SO3H loadings. The aromatic phenyl rings that composed the mesoporous hybrid organosilica walls of the Ph-PMO-PrSO3H materials does not confer to the sulfonic groups a stronger acidity since a very low difference was observed between the ν8a vibration wavenumbers of the DMPH+ molecule of SBA-15-PrSO3H and Ph-PMO-PrSO3H catalysts. The strength of the acid sites is influenced by the close SiOH or SO3H environment. The HI values are slightly superior for Ph-PMO-PrSO3H solid than for SBA-15-PrSO3H sample even when trimethylsilyl groups are incorporated in this latter catalyst. The HI values decrease a lot as a function of increasing concentration of hydrophilic SO3H groups.

Proton-conducting electrolyte membranes based on organosiloxane network/sulfonated poly(ether ether ketone) interpenetrating polymer networks embedding sulfonated mesoporous benzene–silica

Composite membranes based on organosiloxane network (OSPN)/sulfonated poly(ether ether ketone) (SPEEK) interpenetrating polymer network (IPN) structures with sulfonated mesoporous benzene–silica (SMBS) proton conductors embedded are fabricated. The flexibility and toughness properties of OSPN are expected to compensate for the brittleness of the sPEEK membranes. The 2D-hexagonal cylindrical mesopore structures of SMBS maintain the water content at a high level to enhance the conductivity, even at low relative humidity. Compared to the pristine sPEEK membranes, the ternary composite membranes can endure about 10 times more elongation before breaking. Both OSPN and SMBS components enhance the proton conductivity of sPEEK membranes in a hydrated state, while maintaining the water uptake at below 55% even at temperatures as high as 100 °C. The SAXS patterns of the composite membranes explain the water-related membrane properties of composite membranes. The maximum power densities of Nafion membrane-based MEAs are 178.4 mA cm−2, 132.2 mA cm−2, and 90.9 mA cm−2, but those of composite membrane-based ones are 159.1 mA cm−2, 134.2 mA cm−2, and 110.8 mA cm−2 at 95%, 70%, and 45% relative humidity, respectively.

Benzene-Silica with Hexagonal and Cubic Ordered Mesostructures Synthesized in the Presence of Block Copolymers and Weak Acid Catalysts

Highly ordered mesoporous benzene–silicas with 2D hexagonal (p6mm) and 3D cubic (Im3m) symmetry were prepared using weaker acids than hydrochloric acid in the presence of Pluronic P123 and F127 triblock copolymer templates. The resulting ordered mesostructures of 1,4-bis(triethoxysilyl)benzene (BTEB) were well-organized when iron(III) chloride hexahydrate (weak Bronsted acid with Ka = 6.3 × 10–3) was employed; 2D hexagonal structure was obtained at the concentration exceeding 0.064 M (pH ≤1.76) and 3D cubic structure was obtained at the concentration about 0.112 M (pH ≤1.63). The specific surface areas and pore diameters of the hexagonal benzene–silicas studied were in the range from 707 to 966 m2 g–1 and from 7.5 to 8.2 nm, respectively; the corresponding values for cubic benzene–silicas were 514–604 m2 g–1 and 8.5–9.0 nm, respectively. Also, type IV nitrogen adsorption–desorption isotherms and very narrow pore size distributions were obtained for these materials, which are similar to those for mesoporou...

Understanding the high catalytic activity of propylsulfonic acid-functionalized periodic mesoporous benzenesilicas by high-resolution 1H solid-state NMR spectroscopy

Download options Please wait... Supplementary files Supplementary information PDF (192K) Article information DOI https://doi.org/10.1039/C2JM15015H Article type Paper Submitted 05 Oct 2011 Accepted 28 Jan 2012 First published 08 Mar 2012 Download Citation J. Mater. Chem., 2012,22, 7412-7419 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Understanding the high catalytic activity of propylsulfonic acid-functionalized periodic mesoporous benzenesilicas by high-resolution 1H solid-state NMR spectroscopy R. Siegel, E. Domingues, R. De Sousa, F. Jérôme, C. M. Morais, N. Bion, P. Ferreira and L. Mafra, J. Mater. Chem., 2012, 22, 7412 DOI: 10.1039/C2JM15015H To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author Renée Siegel Eddy Domingues Rodolphe De Sousa François Jérôme Cláudia M. Morais Nicolas Bion Paula Ferreira Luís Mafra

Sulfonated PEEK/cubic ( Im3 m) mesoporous benzene–silica composite membranes operable at low humidity

The effects of three-dimensional cubic ( Im3 m) structured mesoporous benzene–silica materials inside a sulfonated poly(ether ether ketone) (sPEEK) polymer matrix are investigated for application as proton exchange membranes in a direct methanol fuel cell (DMFC) system. Cubic ( Im3 m) structured mesoporous benzene–silica is prepared in the presence of a Pluronic F127 PEO-PPO-PEO template under acidic conditions and sulfonated with ~ 98% sulfuric acid using a post-grafting method. The sulfonated mesoporous materials are mixed with a sPEEK (65% of sulfonation degree) polymer matrix using a solvent casting method. These composite membranes exhibit much lower methanol crossovers (3.0~–5.0 × 10 − 7 cm 2 s − 1 ) than a commercial Nafion®117 membrane (1.6 × 10 − 6 cm 2 s − 1 ). Additionally, the composite membranes exhibit higher proton conductivities than a pristine sPEEK membrane and show more stable conductivities than Nafion®117 at a low humidity and high temperatures. For instance, the proton conductivity of Nafion®117 rapidly drop at a relative humidity of 40% and temperatures above 60 °C, whereas the conductivity of the composite membranes increase up to 70 °C, while maintaining similar values up to 80 °C. The high water-absorption and water-retention capacities for the sPEEK/mesoporous material composite membranes are quantified in order to support the results for the different water uptake and proton conductivities.

Direct synthesis of dimethyl carbonate from methanol and carbon dioxide over organotin-functionalized mesoporous benzene-silica

Ordered periodic mesoporous benzene-silicas (Ph-PMOs) functionalized with organotin were synthesized by co-condensing (MeO)2ClSi(CH2)3SnCl3, tetraethyl orthosilicate (TEOS), and 1,4-bis(triethoxysilyl)-benzene in a Pluronic 123 acid solution. The diffraction lines for (100), (110), and (200) facets observed in their X-ray diffraction (XRD) patterns and parallel channels in their transmission electron microscopy (TEM) images show that the samples have highly ordered hexagonal array structure. The presence of bands characteristic for phenyl groups, tetrahedral and octahedral Sn species, and Qn and Tn species in their Fourier transform/infrared (FT/IR), diffuse reflectance UV–vis, and NMR spectra gives convincing evidence for the incorporation of phenyl groups and (MeO)2ClSi(CH2)3SnCl3 into the framework or silica wall. The organotin-functionalized Ph-PMOs exhibit much higher catalytic activity than organotin-functionalized mesoporous silica lacking phenyl groups in the framework, for direct synthesis of dimethyl carbonate (DMC) from methanol and CO2, although both have high catalytic stability. This may be attributed to its enhanced surface hydro-phobicity and the presence of a large number of hexa-coordinated Sn species and tiny Sn oxide clusters in the former sample. The DMC yield obtained over the prepared organotin-functionalized Ph-PMOs increases monotonically with increasing CO2 pressure. The material also exhibits high catalytic stability upon reusage.

Direct synthesis of bifunctional periodic mesoporous benzene-silicas functionalized with a high loading of carboxylic acid groups

Well-ordered periodic mesoporous benzene-silicas functionalized with a high loading of pendant carboxylic acid groups (up to 60 mol% based on silica) have been successfully synthesized via co-condensation of 1,4-bis(triethoxysilyl)benzene and carboxyethylsilanetriol sodium salt using Pluronic P123 as a template and KCl as an additive.

Enhanced transport performance of sulfonated mesoporous benzene-silica incorporated poly(ether ether ketone) composite membranes for fuel cell application

Sulfonated poly(ether ether ketone) (sPEEK)/mesoporous benzene-silica electrolyte composite membranes were prepared using a solvent casting method. The two components were mixed thoroughly in N, N-dimethyl acetamide, at various concentrations up to 20 wt% of the mesoporous benzene-silica powder. The degree of sulfonation was 65% for sPEEK, and the ion-exchange capacity of mesoporous benzene-silica was 0.60 mequiv./g. The mesoporous benzene-silica material had a 2D hexagonal ( p6 mm) mesostructure with a pore diameter of 2.7 nm. The composite membranes exhibited higher proton conductivities than a pristine sPEEK membrane, and the proton conductivity increased with temperature. However, the sPEEK-based composite membranes showed very low methanol crossover below 5 × 10 −7 cm 2/s, but this value was still in the same range as the pristine sPEEK membrane. A maximum proton conductivity of 0.079 S/cm was obtained for the sPEEK-OMB15 membrane at 80 °C, and the highest DMFC cell performance was at 56 mW/cm 2, which were approximately 119 and 37% increases compared to the pristine sPEEK membrane, respectively.

Sulfonated Mesoporous Benzene-Silica as an Acid Catalyst

A sulfonic acid functionalized phenylene-bridged periodic mesoporous organosilica (Ph-PMO-SO3H) catalyzed the reaction of indoles 1 with benzaldehyde (2) in water to give the corresponding bis(indolyl)methanes 3 in 65-95% yield (9 examples, eq. 1). The catalyst was recycled five times without loss of catalytic activity for the formation of 3a (6th run; 90% yield). Ph-PMO-SO3H also catalyzed the etherification of glycerin (4) with 1-phenylpropan-1-ol (5) to afford monoethers 6 in 85% yield (eq. 2).

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.

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 ...

Enhanced benzene selectivity of mesoporous silica SPV sensors by incorporating phenylene groups in the silica framework

A stable and high ordered benzene–silica hybrid mesoporous material was successfully prepared from alternating hydrophilic and hydrophobic materials, composed of silica and benzene. The resulting mesoporous benzene modified silica thin film was then constructed on the surface photovoltage (SPV) sensor. Good response behaviors have shown that the device can be used, at room temperature, as a selective detector of benzene compound in the range of 100–800 ppm. The sensors allowed enhancement of the benzene selectivity, which indicates that the benzene chain within the wall of mesoporous benzene–silica may make an inter-reaction with benzene molecules to yield higher selectivity compared to methanol compound.

Sulfonic acid functionalized crystal-like mesoporous benzene–silica as a remarkable water-tolerant catalyst

Here we report that sulfonated crystal-like benzene-silica is much more robust and active than conventionally used periodic mesoporous silica for catalyzing aqueous organic reactions.