Low-angle X-ray Powder Diffraction Research Articles

Application of magnetic ion imprinted polymers for simultaneous quantification of Al3+ and Be2+ ions using the mean centering of ratio spectra method

Magnetic solid-phase extraction (MSPE) coupled with the spectrophotometric method for the simultaneous quantification of aluminum and beryllium ions based on mean centering of ratio (MCR) method is reported in the current work, for the first time. Two new magnetic ion-imprinted polymers (MIIPs) were synthesized using Chrome Azurol S as the ligand, (3-aminopropyl)triethoxysilane (APTES) as the functional monomer, tetraethyl orthosilicate (TEOS) as the cross-linker, and aluminum and beryllium ions as the templates, and used as magnetic sorbents. The characteristic properties of MIIPs were investigated using FT-IR spectroscopy, field emission scanning electron microscopy (FE-SEM), low angle X-ray powder diffraction (XRD), and energy-dispersive x-ray spectroscopy (EDS). Through this study, factors influencing the MSPE were studied and optimized. The proposed method exhibited good performance, with the linearity of 5.0–50.0 ng mL−1 for aluminum ion and 2.0–40.0 ng mL−1 for beryllium ion as well as the detection limits (DLs) of 3.2 and 0.9 ng mL−1 for aluminum and beryllium ions, respectively. At the end of the study, the capability of the developed method for determination of target analytes was evaluated by its application in the tap and river water samples.

Magnetic ethyl-based mesoporous organosilica composite supported IL/Mn: A novel and highly recoverable nanocatalyst for preparation of 4H-pyrans

A novel magnetic bifunctional ethyl-based periodic mesoporous organosilica supported ionic liquid/manganese complex (Mag-BPMO/Mn) with core–shell structure was synthesized and characterized. The Mag-BPMO/Mn was prepared via grafting of ionic liquid on magnetic Et-based PMO followed by treatment with Mn(NO3)2•4H2O. The physiochemical properties of this nanocatalyst was studied by using Fourier transform infrared (FT-IR) spectroscopy, low angle powder X-ray diffraction (LAPXRD), wide-angle PXRD, energy-dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) analyses. The Mag-BPMO/Mn was applied as an efficient and reusable heterogeneous nanocatalyst for green synthesis of 4H-pyran derivatives via a one‐pot three‐component reaction. The effect of several parameters such as catalyst loading and solvent were investigated in the catalytic process. The recoverability and reusability of the designed Mag-BPMO/Mn nanocatalyst were also studied under applied conditions.

Magnetic methylene-based mesoporous organosilica composite-supported IL/Pd: a powerful and highly recoverable catalyst for oxidative coupling of phenols and naphthols

A novel magnetic methylene-based mesoporous organosilica composite-supported IL/Pd complex (Fe3O4@MePMO-IL/Pd) was synthesized and characterized, and its catalytic performance was investigated. The preparation of the Fe3O4@MePMO composite was achieved through coating of Fe3O4 nanoparticles with a mixture of tetramethoxysilane, bis(triethoxysilyl)methane, and (3-chloropropyl)-trimethoxysilane in the presence of cetyltrimethylammonium bromide surfactant. The Fe3O4@MePMO was then modified with alkyl imidazolium ionic liquid and palladium species to deliver the Fe3O4@MePMO-IL/Pd nanocatalyst. This catalyst was characterized using Fourier transform infrared, thermal gravimetric, wide-angle powder X-ray diffraction, low-angle powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometer, energy-dispersive X-ray, and nitrogen adsorption–desorption analyses. The Fe3O4@MePMO-IL/Pd was effectively used as a highly recoverable and durable catalyst for the selective oxidative coupling of phenols and 2-naphthols under aerobic conditions.

Ruthenium-Based Macromolecules as Potential Catalysts in Homogeneous and Heterogeneous Phases for the Utilization of Carbon Dioxide.

Ruthenium-containing tetraphenylporphyrin (Ru-TPP) molecule was prepared, and the structural elucidation was confirmed using 1H nuclear magnetic resonance (NMR), CHN, and mass spectral analyses. The incorporation of ruthenium ion into the cavities of the macromolecule was confirmed from the disappearance of the 1H NMR signal, characteristic of the N–H bond (−2.72 ppm in TPP). The CHN and mass spectral analyses of the ligand and metallomacromolecules are consistent with the theoretically calculated values. The homogeneous Ru-TPP macromolecule is grafted on the surface of aminosilane-, diaminosilane-, and iodosilane-functionalized SBA-15 molecular sieves. The successful grafting of Ru-TPP on functionalized mesoporous molecular sieve materials was evident from low-angle powder X-ray diffraction, 13C magic angle spinning NMR, and scanning electron microscopy–energy-dispersive X-ray analyses. The resultant homogeneous and heterogenized Ru-TPP catalysts were used for the utilization of carbon dioxide (CO2) under moderate reaction conditions. The homogeneous Ru-TPP catalyst showed first-order kinetics with respect to epoxide with the exclusive formation of cyclic carbonate (about 98%) and an activation energy of 16.07 kg/mol, which is much lower than some of the reported catalysts. Ru-TPP grafted on aminosilane- and iodosilane-functionalized materials showed better catalytic activity (above 90% conversion and 83–96% cyclic carbonate selectivity) and reusability for the chosen reaction.

Phenylene and Isatin Based Bifunctional Mesoporous Organosilica Supported Schiff-Base/Manganese Complex: An Efficient and Recoverable Nanocatalyst

A novel bifunctional periodic mesoporous organosilica supported isatin-Schiff-base/manganese complex [BPMO@ISB/Mn(II)] is prepared, characterized and its catalytic performance is investigated in the synthesis of dihydropyrano[3,2-c]chromene derivatives. The BPMO@ISB was prepared via grafting of 3-aminopropyltrimethoxysilane (APTS) on a phenylene based PMO followed by treatment with isatin. The BPMO@ISB was then reacted with Mn(NO3)2·4H2O to afford the BPMO@ISB/Mn(II) nanocatalyst. This catalyst was characterized using Fourier transform infrared (FT-IR) spectroscopy, thermal gravimetric analysis (TGA), energy-dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM), low angle powder X-ray diffraction (LAPXRD) analysis and transmission electron microscopy (TEM). The BPMO@ISB/Mn(II) nanocatalyst was successfully used in one-pot synthesis of 3,4-dihydropyrano[c]chromene derivatives at room temperature. In addition, the stability, recyclability and reusability of designed nanocatalyst were studied under applied conditions.

A novel method of synthesis and a new insight into the vanadium incorporation in three dimensional mesoporous KIT-6

A nano-crystalline three-dimensional mesoporous KIT-6 and V-KIT-6 materials are synthesized through a new sol-gel method. The above-synthesized materials are characterized by various advanced techniques. The mesoporosity is confirmed by Low angle Powder x-ray diffraction, BET-surface area analysis, and Transmission electron microscopic analysis. The vanadium incorporation is established by Field emission scanning electron microscopy, Fourier transform Infrared spectroscopy, Raman spectroscopy, Electron spin resonance spectroscopy and Ultraviolet-visible diffuse reflectance spectroscopy. V-KIT-6 catalyzes cyclohexane oxidation using H2O2 and gives cyclohexanol and cyclohexanone as the products. The conversion (83% in 1 h) is remarkably higher in its class of compounds due to the presence of three-dimensional mesoporosity. The catalysts are found to be stable even after five successive cycles. A plausible vanadium species and catalytic reaction mechanism are also proposed.

Synthesis, characterization and catalytic application of a novel ethyl and boron sulfonic acid based bifunctional periodic mesoporous organosilica

Abstract A novel ethyl and boron sulfonic acid based bifunctional periodic mesoporous organosilica [BPMO-Et-B(OSO3H)2] with dual Lewis-protic acidic sites was prepared, characterized and applied as efficient nanocatalyst for the synthesis of tetrahydrobenzo[b]pyrans. The BPMO-Et-B(OSO3H)2 was prepared by the chemical attachment of boric acid [B(OH)3] on an ethyl-based periodic mesoporous organosilica (PMO-Et) followed by treatment with chlorosulfonic acid (ClSO3H) at room temperature. This nanocatalyst was characterized using Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA), low-angle powder X-ray diffraction (LAPXRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and transmission electron microscopy (TEM). The BPMO-Et-B(OSO3H)2 was shown to be a highly efficient nanocatalyst for three-component synthesis of tetrahydrobenzo[b]pyran derivatives at room temperature under solvent-free conditions. Moreover, the BPMO-Et-B(OSO3H)2 was recovered and reused at least 8 times without significant decrease in its activity.

Development of Mn or Fe sulfides in the interlayer space of raw and Al-pillared bentonite

Preparation of metal sulfide nanoclusters (Mn or Fe) confined in the interlayer space of a bentonite either with or without previous Al2O3-pillaring was investigated by H2S-sulfidization of Mn²⁺- or Fe²⁺-exchanged Al2O3-pillared bentonite as potential strategy to control growth and mean final size of interlayered, MnS or FeS-like polynuclear nanoclusters. The materials were characterized by elemental analysis, cation exchange capacity, low-angle powder X-ray Diffraction, N2 adsorption isotherms, simultaneous thermal analysis (DTA/TGA), diffuse reflectance UV-vis spectroscopy and high-resolution X-ray photoelectron spectroscopy. Interlayered metal sulfides were successfully obtained in pretty short time of reaction (only ~12 h). Optimal set of preparation conditions was established promoting stabilization of the interlayered metal sulfides, whereas preserving typical layered stacking of the starting clay: (i) ratio H2S/M²⁺(incorporated) = 50 mol/mol (M = Mn²⁺ or Fe²⁺); (ii) temperature of sulfidization = 100 °C; (iii) 200 °C for final thermal treatment, irrespective the type of atmosphere used (inert-N2 or oxidizing-air) and (iv) acid-base neutralization prior to thermal treatment did not enhance thermal stability. The most efficient Al-pillaring was achieved with 20 meq Al³⁺/g clay in terms of both higher XRD 001 basal reflection and narrower distribution of alumina-pillars. HR-XPS and DR-UV-vis analyses of the best materials with every transition metal evidenced formation of polysulfide groups and blue-shift of the absorption signal as a consequence of the modification performed on the layered aluminosilicate. Development of Mn or Fe sulfides in the interlayer space of.... Available from: https://www.researchgate.net/publication/323399710_Development_of_Mn_or_Fe_sulfides_in_the_interlayer_space_of_raw_and_Al-pillared_bentonite [accessed Apr 18 2018].

Natural clay attapulgite as the raw material for synthesis of Al/Ti/Mg-containing mesoporous silicates with cubic, 3D hexagonal, and lamellar mesostructures

A series of Al/Ti/Mg-containing ordered mesostructured silicates were synthesized using the natural attapulgite clay as the raw material, which was first pretreated by 4 M hydrochloric acid without other special treatment such as grinding. By varying the pH value in the synthetic gel, different mesophases with cubic, 3D hexagonal, and lamellar mesostructures were obtained. Their mesostructures were confirmed by low-angle X-ray diffraction (XRD) and transmission electron microscopy (TEM). Their morphology and textural properties were analyzed by scanning electron microscopy (SEM) and N2 adsorption. It was found that the hetero-atoms including Al, Ti, and Mg in the clay could be effectively transformed into these ordered mesostructured silicate frameworks in sufficient content, as revealed by inductively coupled plasma (ICP) emission spectroscopy and fourier transform infrared (FT-IR) spectrum. NH3-TPD showed the accessibility of Al species as Bronsted and Lewis acid sites in the mesostructured framework located on the pore surface. All above suggests the potential of attapulgite as a low-cost precursor for the industrial scale production of high quality heteroatom-doped mesophases for various applications. Low-angle powder X-ray diffraction patterns of mesostructured silicates with cubic, 3D hexagonal, and lamellar mesophases, synthesized by using natural clay attapulgite as raw material: uncalcined (left) and calcined (right).

Highly efficient and recyclable basic ionic liquids supported on SBA-15 for the synthesis of substituted styrenes, carbinolamides, and naphthopyrans

In this study, highly stable mesoporous silica, SBA-15, was prepared and used as a support to functionalize ionic liquids. Triazole and N,N-dimethylaminopyridine were functionalized on the surface of SBA-15 through surface silanol groups of SBA-15 to obtain basic ionic liquids. In order to obtain high basicity, −OH containing basic ionic liquids, based on triazole and N,N-dimethylaminopyridine, were prepared. Catalysts were characterized by the complementary combination of low angle powder X-ray diffraction, N2-adsorption, electron microscopes, Fourier-transform infrared spectroscopy, thermal gravimetric analysis, elemental analysis, and temperature programme desorption techniques. Systematic assessment of the catalytic activity was made using Knoevenagel condensation reaction for the synthesis of substituted styrenes. Application of these catalysts was also evaluated in the synthesis of carbinolamides. Recycling study shows that no significant decrease in the catalytic activity was observed after five recycles. Finally, application of the highly active basic ionic liquid was evaluated in one-pot, two-step tandem reaction for the synthesis naphthopyrans.

Monodisperse mesoporous silica nanospheres with radially oriented mesochannels and their size effect on cell uptake

A facile one-pot sol–gel approach was reported for the synthesis of monodisperse silica nanospheres (MSNs) with radially oriented mesochannels, tunable diameter ranging from 280 to 500nm, by using cetyl trimethylammonium bromide (CTAB) as structure-directing agent, different amount of tetraethyl orthosilicate (TEOS) as the silica source and concentrated ammonia solution as the basic catalyst. Characterization and measurement using field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), low angle X-ray powder diffraction (LA-XRD) and nitrogen adsorption–desorption reveal that the obtained monodisperse MSNs have uniform, radially aligned mesopore of about 2.3nm, high surface area (about 960m2/g) and large pore volume of 0.58cm3/g. Cell experiments indicate that, they obtained MSNs possess excellent biocompatibility and the smaller MSNs have relatively lower cytotoxicity.

Novel ion imprinted polymer magnetic mesoporous silica nano-particles for selective separation and determination of lead ions in food samples

A novel Pb(II) ion imprinted polymer coated on magnetic mesoporous silica was synthesised and characterised by scanning electron microscopy (SEM), thermal gravimetric/differential thermal analysis (TG/DTA), elemental analysis (CHN) and low angle X-ray powder diffraction (XRD). The application of this sorbent was investigated in preconcentration and determination of low concentrations of lead ions. Through this study, various effective factors on determination, such as pH of the sample solution, eluent including type, concentration and volume, adsorption and desorption time which are effective on the method efficiency, were appraised. In order to investigate the selectivity of this sorbent toward Pb(II) ions, the effect of variety of ions on preconcentration and recovery of Pb(II) ions were also investigated. The limit of detection (LOD) was found to be lower than 1.3μgL−1 and the recovery and relative standard deviation (RSD%) of the method were higher than 97.3% and lower than 2.9%, respectively. The application of this sorbent was investigated in separation and determination of lead-contaminated food with concentration below the detection limit of flame atomic adsorption spectroscopy. Validation of the presented method was performed by analysing several standard reference materials with certified lead concentrations.

Ce/SBA-15 as a heterogeneous ozonation catalyst for efficient mineralization of dimethyl phthalate

The catalytic activity of cerium-loaded SBA-15 (Ce/SBA-15) for the ozonation of dimethyl phthalate (DMP) in aqueous solution was studied. Ce/SBA-15 was prepared and characterized by a low angle X-ray powder diffraction (XRD), nitrogen adsorption–desorption and ultraviolet–visible diffuse reflection spectrum (UV–vis DRS). The results showed that the material retained a highly ordered mesoporous structure and processed large surface area. The presence of Ce/SBA-15 slightly accelerated DMP decomposition, but significantly improved its mineralization efficiency. Under the chosen condition, a high mineralization efficiency (88.7%) was achieved by Ce/SBA-15/O3 process at 60min, 2.6 times higher than SBA-15/O3, 3.5 times higher than O3 alone. The comparison among different process indicated that the combination of Ce/SBA-15 and O3 exhibited a significant synergetic effect. Ce/SBA-15 significantly improved ozone decomposition into hydroxyl radicals in aqueous solution and the oxidation of DMP occurred via the free radical mechanism. The reused experiment verified that Ce/SBA-15 kept a good catalytic activity and stability, and it was a promising heterogeneous catalyst.

Determination of Pb(II) Ions Using Novel Ion-Imprinted Polymer Magnetic Nanoparticles: Investigation of the Relation Between Pb(II) Ions in Cow’s Milk and Their Nutrition

The application of novel Pb(II) ion-imprinted polymer coated on magnetic mesoporous silica was investigated in preconcentration and determination of low level of Pb(II) ions. The job proposed a new method for preconcentration and determination of Pb(II) ions. This novel sorbent was characterized by scanning electron microscopy, thermal gravimetric/differential thermal analysis, elemental analysis, and low-angle X-ray powder diffraction. Effects of various factors such as the effects of the pH of sample solution, eluent (include type, concentration and volume), adsorption and desorption time which are effective in method efficiency, were appraised through this study. In order to investigate the selectivity of this sorbent toward Pb(II) ion, the effects of variety of foreign ions interfering on preconcentration and recovery of Pb(II) ions were also investigated. The limit of detection (LOD) was found to be 0.7 μg L−1 and the recovery and relative standard deviation of the method were 96.6–102.4 % and 1.3–3.3 %, respectively. Validation of the outlined method was performed by analyzing several standard reference materials with certified Pb(II) concentrations. Finally, this sorbent was applied for separation and determination of Pb(II) ion in grass and cow’s milk, which showed their lead concentration to be below the detection limit of flame atomic adsorption spectroscopy.

Synthesis of ZnFe2O4 Nanoparticles Confined Within Nanoporous Silica Using Trinuclear Oxo-centered Complex: Inorganic Complexes as a Precursor for the Preparation of Magnetic Nanoporous Silica

MCM-48 Nanoporous silica (Mobil Composition of Matter, #48) was synthesized and functionalized by pyridine groups. The formation of this functionalized nanoporous silica was confirmed by elemental analysis, low angle x-ray powder diffraction and N2 adsorption. The trinuclear oxo-centered Fe2Zn(μ3-O)(CF3COO)6(H2O)3 cluster was synthesized and immobilized inside the pyridine functionalized MCM-48 pores. The immobilization of this cluster was confirmed by IR spectroscopy and flame atomic adsorption spectroscopy. Fe2ZnO4 nanoparticles were confined within the nanoporous silica pores by thermolysis of the immobilized Fe2Zn(μ3-O)(CF3COO)6(H2O)3 cluster and were characterized by high angle X-ray powder diffraction and high resolution transmission electron microscopy. This method is suitable for the one-pot preparation of Fe2ZnO4 confined nanoporous silica.

Synthesis of cerium-doped MCM-41 for ozonation of p-chlorobenzoic acid in aqueous solution

Cerium-doped MCM-41 (Ce-MCM-41) was prepared by a hydrothermal method and its catalytic activity for ozonation of p-chlorobenzoic acid (p-CBA) in aqueous solution was studied. For comparison, cerium-loaded MCM-41 (Ce/MCM-41) was prepared by a dipping method. Ce-MCM-41 was characterized by the low and wide angle X-ray powder diffraction (XRD), nitrogen adsorption–desorption, transmission electron microscopy (TEM) and ultraviolet–visible diffuse reflection spectrum (UV–vis DRS). The results showed that the material retained the highly ordered mesopore structure of MCM-41 and had a surface area of 852m2g−1. Cerium was incorporated into the framework of MCM-41, locating at tetrahedrally coordinated sites. The cerium doping content, initial pH of aqueous solution and reaction temperature played important roles in catalytic ozonation of p-CBA. Under the chosen conditions (1.39mgl−1 ozone dosage, 10mgl−1p-CBA solution and 1gl−1 catalyst dosage), the high mineralization rate (86%) was achieved by Ce-MCM-41/O3 process at 60min reaction time, only 52% by O3 alone. The combination of Ce-MCM-41 and O3 exhibited a significant synergetic effect. Ce-MCM-41 showed the better activity and stability than cerium-loaded MCM-41(Ce/MCM-41) during catalytic ozonation of p-CBA, its cerium leaching was greatly reduced (only 0.085mgl−1) and below detection limit after being reused, compared with that of Ce/MCM-41 (0.44mgl−1) with the presence of the same theoretical cerium content. TOC removal rate slightly decreased from 86% to 81% and kept stable after Ce-MCM-41 being re-utilized two times, which illustrated that Ce-MCM-41 was a kind of promising catalyst for ozonation of p-CBA. The addition of Ce-MCM-41 significantly improved ozone decomposition into HO in aqueous solution and reduced ozone concentration in equilibrium.

Catalytic activity of Fe/SBA-15 for ozonation of dimethyl phthalate in aqueous solution

The catalytic activity of iron-loaded SBA-15 (Fe/SBA-15) for ozonation of dimethyl phthalate (DMP) in aqueous solution was investigated. SBA-15 was synthesized by a hydrothermal method and Fe/SBA-15 was prepared by an incipient wetness impregnation method. The materials were characterized by a low and wide angle X-ray powder diffraction (XRD), N2 adsorption–desorption, and atomic absorption spectrometer (AAS). Under the chosen conditions (50mgh−1 ozone dosage, 10mgl−1 DMP solution and 0.20gl−1 catalyst dosage), Fe/SBA-15/O3 process obviously improved DMP and total organic carbon (TOC) removal efficiency due to the generation of hydroxyl radical (HO), which was approved by tert-butanol (TBA). The mineralization of DMP followed an apparent first-order kinetics. The rate constant in Fe/SBA-15/O3 was 0.0058min−1, 3.9 times higher than that of O3 alone, 3.4 and 1.9 times higher than those of SBA-15/O3 and Fe2O3/O3 processes respectively. The iron content, reaction temperature and initial pH of DMP solution played important roles in Fe/SBA-15/O3 process, while chloride ion exhibited the slight influence. The synergetic effect between O3 and Fe/SBA-15 adsorption illustrates that Fe/SBA-15 is a promising catalyst for ozonation process.

Titania–silica–phosphonate triconstituent hybrid mesoporous materials as adsorbents in gas and liquid phases

Mesoporous titania–silica–phosphonate (TSP) hybrid materials with different Si/Ti molar ratios have been synthesized by triconstituent assembly through oil-in-water microemulsion strategy with the use of Si(OEt)4, TiCl4 and sodium salt of ethylene diamine tetra(methylene phosphonic acid) as Si, Ti and P sources, respectively, and cetyltrimethylammonium bromide as surfactant template. The integration of silica into titania–phosphonate hybrids resulted in the improvement of regularity of mesoporous structure and the enlargement of surface area and pore volume of the hybrid materials, confirmed by low-angle powder X-ray diffraction, transmission electron microscopy and nitrogen adsorption–desorption analysis. The synthesized TSP triconstituent hybrid mesoporous materials have a preferable BET surface area up to 670m2/g with large pore volume of 1.1cm3/g. And the adsorption measurements of the synthesized TSP materials for CO2 in gas phase and Cd(II) ions in liquid phase were tested, indicating their potential applications as multifunctional adsorbents for environmental protection.

Predictive synthesis of ordered mesoporous silica with maltoside and cationic surfactants based on aqueous lyotropic phase behavior

Self-assembled nonionic alkyl glycoside surfactants are of interest for creating functional adsorption and catalytic sites at the surface of mesoporous sol-gel-derived materials, but they typically impart poor long-range order when they are used as pore templates. Improved order and control over the functional site density can be achieved by mixing the alkyl polyglycoside surfactant with a cationic surfactant. Here, we investigate the rarely reported lyotropic liquid crystalline (LLC) phase behavior of aqueous solutions of a nonionic disaccharide surfactant, n-dodecyl-beta-d-maltoside (C(12)G(2)/DM), and cetyltrimethylammonium bromide (C(16)TAB) by low-angle powder X-ray diffraction (XRD) and polarized optical microscopy (POM). An approximate ternary phase diagram of the C(16)TAB-C(12)G(2)-water system is developed at 50 degrees C, which includes 2-D hexagonal (P6mm symmetry), bicontinuous cubic (Ia3 d symmetry), lamellar, and rectangular (cmm symmetry) LLC phases. By replacing the volume of water in the phase diagram with an equivalent volume of silica, ordered mesoporous materials are prepared by a nanocasting technique with variable C(12)G(2)/C(16)TAB ratios. For large regions of the phase diagram, this approach is predictive. However, silica materials synthesized with comparatively high C(12)G(2)/C(16)TAB ratios are only poorly ordered in a way that does not correspond to their lyotropic liquid crystalline phase behavior. Also, in contrast with our previous study of mixed C(16)TAB/n-octyl-b-d-glucopyranoside templating [37] the boundary between hexagonal and bicontinuous cubic materials is shifted towards higher surfactant content than in the aqueous LLC system.

Cage-like ordered mesoporous organosilicas with isocyanurate bridging groups: Synthesis, template removal and structural properties

The removal of triblock copolymer template from SBA-16 cage-like ordered mesoporous organosilicas (OMOs) functionalized with bulky isocyanurate (ICS) heterocyclic bridging groups is examined. These isocyanurate-containing OMOs (ICS–OMOs) were prepared by co-condensation synthesis of tris[3-(trimethoxysilyl)propyl]isocyanurate and tetraethyl orthosilicate in the presence of poly(ethylene oxide)- block-poly(propylene oxide)- block-poly(ethylene oxide) (EO 106PO 70EO 106) triblock copolymer F127 used as a template and sodium chloride additive under low acidic conditions. Initial studies revealed that the extracted ICS–OMOs materials have a cubic structure ( Im3m symmetry), high contents of isocyanurate bridging groups (0.76 and 1.08 mmol/g) as well as pore diameters ranging from 6.6 to 7.2 nm. The effect of the heating temperature on the structural ordering, specific surface area, pore volume and cage pore diameter of the as-synthesized and extracted ICS–OMOs was investigated. In addition, the synthesis, characterization and template removal of a bifunctional cage-like periodic mesoporous organosilica (PMO) containing ethane (E) and isocyanurate bridging groups is discussed. The E–ICS–PMO samples were fabricated via one-pot synthesis using 1,2-bis(triethoxysilyl)ethane, tris[3-(trimethoxysilyl)propyl]isocyanurate and F127 block copolymer. The resulting ICS–OMOs and E–ICS–PMOs were characterized by nitrogen adsorption–desorption isotherms at −196 °C, small-angle X-ray scattering (SAXS) or low-angle powder X-ray diffraction (XRD), high-resolution thermogravimetry (TG), Fourier-transform infrared spectroscopy (FT-IR) and CHNS elemental analysis. The SAXS/XRD and nitrogen adsorption show that the use of a short extraction and temperature-controlled heating at 315 °C in flowing nitrogen is an effective way to remove the remaining polymeric template from cubic mesostructures without decomposition of isocyanurate bridging groups, as evidenced by FT-IR, TGA and CHNS analysis. Moreover, a complete thermal degradation of isocyanurate groups at 550 °C in air has led to a significant shrinkage of the mesostructure, however its ordered nature was retained.