Mesoporous Organosilicate Research Articles

Magnetic Mesoporous Organo-Silicate Composite for Removing Organic Dyes from Aqueous Media

Water pollution has become a major problem for our modern ecological systems. According to the UN’s program on the environment, 80% of wastewater generated by humans goes untreated. This water contains pollutants ranging from human waste to industrial. When it eventually makes it into our waterways, it can have devastating effects on the ecosystem and potentially cause mass die off of the majority of organisms that reside there. The ones that remain are often wrought with disease and genetic mutation that can affect and destroy future generations. To make matters worse, the pollutants can remain viable and have destructive effects for years after their initial dumping. The Center for Public Integrity found that after 35,000 tons of industrial car waste was dumped onto occupied lands, the ground water was still found to be toxic 43 years later. For these reasons, cheap and effective ways of being able to remove pollutants, such as metals and dyes, is in high demand. One potential way of achieving this is using readily available adsorbent materials. Adsorbent materials can collect these pollutants, binding them, and making it easier for traditional filters to remove them from water sources [1-10]. The downside to these materials is that they are typically expensive to synthesize, have a low absorbance capacity. Magnetic Mesoporous Organo-Silicate (MMOS) Composite is a potential material that can get around these pressing issues. Mesoporous silicate has an organic function group with a high surface area. Although relatively ineffective on its own, combination with magnetic proprieties based on Fe3O4 and organic site based on cetrimonium bromide has been shown to be promising for the adsorption of water pollutants. In initial trials, the MSC composite has shown great promise in removing high concentrations of organic dyes from water sources. Additionally, this material has shown some effect in removing certain metal ions from aqueous solution. MSC was found to have a high absorbance capacity even at low dosages. Isotherm studies showed MCS was capable of removing 93% of Congo Red (CR) at high concentrations of adsorbent, while Methylene Blue (MB) showed 82% removal at high adsorbent concentrations. Adsorption was modeled using the Langmuir and Freundlich isotherm models in order to both describe the equilibrium isotherm and determine isotherm constants. Adsorption modeling found that CR fits to the Langmuir Model while MB fits to the Freundlich Model. Kinetics testing determined that MCS follows a first order reaction model for CR and a zero-order reaction model for MB. Future research into this material can look at alterations to its structure that would make it more viable for metal ions. References H Namkoong, E Biehler, G Namkoong, TM Abdel-Fattah, ACS omega 7 (44), 39931-39937 (2022)Omar H. Elsayed-Ali, Hani E. Elsayed-Ali and Tarek M. Abdel-Fattah, Journal of Hazardous Materials, 185 (2-3), 1550-1557 (2011).Alya Elsayed-Ali, Tarek Abdel-Fattah, Hani Elsayled-Ali, Hani, Journal of Chemical Education, 88(8), 1126-1129 (2011).TM Abdel-Fattah, ME Mahmoud, Chemical engineering journal 172 (1), 177-183 (2011)TM Abdel-Fattah, ME Mahmoud, MM Osmam, SB Ahmed, Journal of Environmental Science and health, part A 49 (9), 1064-1076 (2014)ME Mahmoud, AA Yakout, MT Abed El Aziz, MM Osman, TM Abdel-Fattah, Journal of Environmental Science and Health, Part A 50 (10), 1072-1081 (2015)ME Mahmoud, TM Abdel-Fattah, MM Osman, SB Ahmed, Journal of Environmental Science and Health, Part A 47 (1), 130-141 (2012)TM Abdel-Fattah, B Bishop, Journal of Environmental Science and Health, Part A 39 (11-12), 2855-2866 (2004)ME Mahmoud, MM Osman, SB Ahmed, TM Abdel-Fattah, The Scientific World Journal 2012 (2012)ME Mahmoud, SS Haggag, TM Abdel-Fattah, Polyhedron 26 (14), 3956-3962 (2007)

Structural and Luminescence Properties of Eu-Doped PMO Films with Ethylene Bridge and Methyl Terminal Groups

Eu-doped periodic mesoporous organosilicate (PMO) films with terminal methyl and ethylene bridging groups have been synthesized using sol-gel technology and spin-coating, employing evaporation-induced self-assembly (EISA), on silicon wafers. Eu doping is achieved by the dissolution of Eu(NO3)3·6H2O in the precursor solution. The deposited films are characterized using Fourier transform infrared (FTIR) spectroscopy, ellipsometric porosimetry (EP), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy. It is observed that Eu doping reduces the concentration of terminal methyl groups, makes the films more hydrophilic and reduces the pore size and open porosity. The reduction reaction Eu3+ → Eu2+ occurs in the pores of organosilicate glass (OSG) films, which was confirmed by the depth profiling XPS. Eu3+ was still present on the top surface of the films. The presence of Eu3+ and Eu2+ gives luminescence emission in the range of 600–630 nm (Eu3+) and 290–400 nm (Eu2+). The Eu2+/Eu3+ concentrations ratio depends on CH3 groups concentration in the films. The concentration of Eu2+ ions in the pores can be reduced by exposure to inductively coupled (ICP) oxygen plasma. The observed shift in the luminescence spectra towards the UV region, in comparison to previously reported Eu-doped organosilicate films, can be attributed to the energy transfer occurring between the host material and Eu2+ ions.

Versatile Ag2O and ZnO nanomaterials fabricated via annealed Ag-PMOS and ZnO-PMOS: An efficient photocatalysis tool for azo dyes

Numerous semiconductor based photocatalysts have been synthesized but most of them are unable to perform under ordinary light conditions. Herein, we successfully prepared photocatalysts comprising silver and zinc nano oxides (MxOy = Ag2O and ZnO) obtained by annealing silver and zinc supported periodic mesoporous organosilicates (Ag-PMOS and ZnO-PMOS). MxOy proved to be influential photocatalysts for the photo-degradation of methylene blue (MB) and methyl orange (MO) azo dyes from water. After removing organic contents from the parent Ag-PMOS and ZnO-PMOS, the nano Ag2O and ZnO showed 93% and 88 % MB degradations whereas 89% and 73% MO reductions under visible-light. MxOy showed improved photo-degradation competences relative to Ag-PMOS (MB = 81%, MO = 48%) and ZnO-PMOS (MB = 47%, MO = 57%). The efficient results were recovered by recycling of MxOy and exhibited appreciable photo-degradation (MB = 90, 87, 85, and 83% MO = 89, 85, 83 and 80% by Ag2O while MB = 83, 71, 64, and 56% MO = 71, 68, 65 and 60% by ZnO), which pointed towards definite durability of studied nano oxides. The observed exciting consequences favored to these nano oxides as an excellent semiconducting source of electrons for photocatalysis.

Fabrication of Periodic Mesoporous Organo Silicate (PMOS) composites of Ag and ZnO: Photo-catalytic degradation of methylene blue and methyl orange

Water resources are badly affected by industrial effluents containing organic azo dyes. The present study successfully synthesized silver (Ag) and zinc oxide (ZnO) supported periodic mesoporous organosilicates (Ag-PMOS and ZnO-PMOS) for catalytic degradation of methylene blue (MB) and methyl orange (MO). Initially, methyacryl functionalized periodic mesoporous organosilica (PMOS) framed through tween-80 ((T-80) C64H124O26) templates by co-condensation of sodium silicate (Na2SiO3) and 3-methacryloxypropyl trimethoxysilane (C10H20O5Si). Formerly, Ag-PMOS and ZnO-PMOS structured by adsorbing Ag and ZnO on PMOS. The synthesized PMOS, Ag-PMOS and ZnO-PMOS were characterized by XRD, FT-IR, TGA, Photoluminescence (PL) and TEM, which sign posted successful assortment of methyacryl, Ag and ZnO moieties in products. These materials found to have effective surface area proved by 81% and 48%, 47% and 57% competent degradation of MB and MO by Ag-PMOS and ZnO-PMOS respectively. Moreover, significant results of 71% and 45%, 44% and 54% reduction of MB and MO recuperated by recycled Ag-PMOS and ZnO-PMOS respectively. Substantial degradation competency and operative reusability of Ag-PMOS were superior than ZnO-PMOS due to better charge transfer capability and high durability. Outcomes of present work proved that Ag-PMOS and ZnO-PMOS have good catalytic properties for photocatalytic degradation of methylene blue (MB) and methyl orange (MO) under visible lights.

Decorated palladium nanoparticles on mesoporous organosilicate as an efficient catalyst for Sonogashira coupling reaction

Reforming mesoporous silica was provided by the reaction of SBA‐15 with (3-aminopropyl)triethoxysilane, the product of which was treated with furfural to give SBA-propyl-imine-furan. In the next step, palladium chloride was attached to the functionalized SBA‐15, so Pd nanoparticles immobilized on the mentioned catalyst for providing an applicable catalyst to use in the Sonogashira cross-coupling reaction. The high stability and performance of functionalized heterogeneous hybrid catalyst of Pd@SBA-Pr-imine-furan in overall were highly essential. The nano-structured Pd@SBA-Pr-imine-furan catalyst was studied for Sonogashira cross-coupling reaction by phenylacetylene and various aryl halides under reflux conditions with a small amount of catalyst. In comparison with the earlier reports, this paper offered several benefits such as short reaction times, high yields of products, catalyst stability, quick recovery, and catalytic activity for at least seven continuous runs.

Distribution of water in the pores of periodic mesoporous organosilicates - a proton solid state MAS NMR study.

Solid state proton (1H) magic angle spinning (MAS) NMR has been employed to study the distribution of confined water in ethane substituted periodic mesoporous organosilicate (PMOE) materials. Proton spectra acquired at different hydration levels are analysed and interpreted in terms of water clusters of various sizes and distributions of water layers on the pore surface. For comparison, we also performed similar experiments on SBA-15. The formation of larger clusters at lower hydration suggests that the pores of PMOE are getting filled with water at lower hydration levels than those in SBA-15. For PMOE, the simultaneous presence of two major resonances in the ranges 3.6-4.1 ppm and 4.4-5.2 ppm and their behaviour upon hydration imply a water layer distribution that is the sum of two contributions, corresponding to fully filled and partially filled pores or pore segments. Furthermore, the behaviour mentioned above suggests that both radial and axial filling mechanisms play a significant role in the hydration process. For SBA-15, as a function of hydration, we observed a smooth variation in the proton chemical shift of the main dynamic resonance. In accordance with previous studies, this is attributed to the gradual increase in the average thickness of water layers with an increase in hydration, and to a pore filling mechanism that is predominantly radial.

Removal of organic template of mesoporous organosilicate thin films using supercritical carbon dioxide fluids

An organic template of periodic mesoporous organosilicate films was removed using supercritical CO2 fluids that are compressive solvents with a nanopenetration capability. The removal efficiency was evaluated by infrared spectroscopy and refractive index measurements. The removal ratio was dependent on treatment pressure and temperature and improved when the fluid density and/or temperature was high. Because a very high process temperature can deteriorate the organosilicate frame structure, the removal at a low temperature and a high pressure is preferable. The films under supercritical CO2 processing were characterized also in situ ellipsometry. It was found that the removal is a fast process and mostly completes during temperature ramping.

Degradation-Restructuring Induced Anisotropic Epitaxial Growth for Fabrication of Asymmetric Diblock and Triblock Mesoporous Nanocomposites.

A novel degradation-restructuring induced anisotropic epitaxial growth strategy is demonstrated for the synthesis of uniform 1D diblock and triblock silica mesoporous asymmetric nanorods with controllable rod length (50 nm to 2 µm) and very high surface area of 1200 m2 g-1 . The asymmetric diblock mesoporous silica nanocomposites are composed of a 1D mesoporous organosilicate nanorod with highly ordered hexagonal mesostructure, and a closely connected dense SiO2 nanosphere located only on one side of the nanorods. Furthermore, the triblock mesoporous silica nanocomposites constituted by a cubic mesostructured nanocube, a nanosphere with radial mesopores, and a hexagonal mesostructured nanorod can also be fabricated with the anisotropic growth of mesopores. Owing to the ultrahigh surface area, unique 1D mesochannels, and functionality asymmetry, the obtained match-like asymmetric Au-NR@SiO2 &EPMO (EPMO = ethane bridged periodic mesoporous organosilica) mesoporous nanorods can be used as an ideal nanocarrier for the near-infrared photothermal triggered controllable releasing of drug molecules.

Hybrid microporous and mesoporous organosilicate covalent polymers with high porosity

A novel non-hydrolytic sol-gel synthesis of hybrid organosilicates is reported allowing control of micro/mesoporous character of the xerogels by variation of the silicon precursor. The polycondensation reaction of silicon(IV) acetate, Si(OAc)4, with 1,3,5-trihydroxybenzene (THB) in dry dioxane at 100 °C produces acetic acid and highly porous amorphous aromatic organosilicate xerogels. Their apparent BET surface areas are as high as 990 m2 g−1 and the total pore volume is 0.843 cm3 g−1. These materials are mostly microporous with a low abundance of mesopores and an average pore size of 3.5 nm. The reaction of HSi(OAc)3 with THB produced a novel mesoporous material with properties superior to xerogels obtained from Si(OAc)4. The BET surface area of 933 m2 g−1 is retained upon heating and average pore size reached 6.0 nm. The total pore volume of 1.36 cm3 g−1 is the highest value achieved in porous aromatic organosilicates so far and is comparable to values typical for 3D covalent organic networks (COFs). The materials are stable up to 400–500 °C but they are sensitive to hydrolysis in moist air. The reactions of other silicon precursors (MeSi(OAc)3 and tBuSi(OAc)3) and larger polyphenol connectors, 1,3,5-tris(4′-hydroxyphenyl)benzene (THPB), 2,4,6-tris(4′-hydroxyphenyl)-1,3,5-triazine (THPTA), and 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP), produced materials with less satisfactory properties.

Probing the molecular character of periodic mesoporous organosilicates via photoluminescence of Lewis acid-base adducts.

Photoluminescence decay was used as a structure-sensitive method to compare the distribution of emitting sites in periodic mesoporous organosilicates (PMOs) to their respective molecular analogs. The observed close similarity of PL decays confirms the molecular nature of PMOs and high homogeneity of emitting sites.

A facile route to enhance the properties of polymer electrolyte-based organic–inorganic hybrid proton exchange membranes

A series of novel sulfonated polyimide (SPI)-mesoporous organosilicate (MSiSQ) hybrid proton exchange membranes (PEMs) with enhanced properties were prepared by in situ sol–gel process. The MSiSQ was synthesized from 3-isocyanatopropyltriethoxysilane (IPTES) and 8-hydroxyquinoline-5-sulfonic acid (SQ). The microstructure and properties of the hybrid membranes were characterized. The microstructure of the membranes can be regulated by the hydrogen bonds formed by the nitrogen atoms of MSiSQ phase and the hydrogen atoms of sulfonic acid groups in SPI. The uniform distribution of sulfonate ion clusters was observed in the hybrid membranes. The hybrid membranes exhibited superior performance as compared with that of pure SPI membrane such as the proton conductivity, methanol permeability, mechanical properties and thermal stabilities. The SPI-40-MSiSQ membrane showed a maximum proton conductivity of 0.566Scm−1 at 80°C and 100% relative humidity, an optimal selectivity of 12.8×106Sscm−3 and an improved fuel cell performance as compared with pure SPI membranes. These excellent properties could be attributed to the formation of the continuous microstructure and well-connected proton transport channels due to the strong hydrogen bonding interaction and the mesoporous structure in the hybrid membranes.

Hybrid Mesoporous Silicas and Microporous POSS-Based Frameworks Incorporating Evaporation-Induced Self-Assembly.

We fabricated a series of mesoporous silicas and mesoporous organosilicates with hierarchical porosity through evaporation-induced self-assembly using Pluronic F127 as a template in this study. We could tailor the mesophase of each mesoporous silica sample by varying the weight ratio of its two silica sources: tetraethyl orthosilicate (TEOS) and triethoxysilane hydrosilylated octavinyl polyhedral oligomeric silsesquioxane (OV-POSS-SILY). The mesophases ranged from an ordered body-centered cubic (bcc) structure (TEOS alone) to ordered face-centered cubic (fcc) structure (10 and 20 wt.% of OV-POSS-SILY) and finally to disordered spherical pores (≥30 wt.% of OV-POSS-SILY). We used small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) to study the transformations of these mesophases, while N2 isotherm sorption curves revealed the porosities of these mesoporous silicate samples. Moreover, 29Si CP/MAS solid state nuclear magnetic resonance spectroscopy allowed us to analyze the compositions of the POSS-containing silicate frameworks. Such functional mesoporous silica samples incorporating microporous POSS building units have potential applications in various systems, including optical and electronic devices.

Pore size evaluation of mesoporous organosilicate films by non-destructive X-ray reflectivity methods

200-nm-thick organosilicate films deposited by mixture of tetraethyl orthosilicate (TEOS) and methyltrimethoxysilane (MTMS) dissolving in different cetrimonium bromide (CTAB)/ethanol ratios were characterized in terms of pore size determination and its distribution. Under the toluene ambient, the pores would adsorb the gas hence elevating the whole film density. The X-ray reflectivity (XRR) equipped with mass flow control was utilized to detect the film density increasing. By fitting with Gaussian function and conversing with Kelvin’s equation, the pore size was increased from 6.2 to 10.8 Å as the CTAB/ethanol ratio increasing to 0.075. It was attributed to the ethanol and CTAB enhanced the TEOS hollow droplets stability and dissolvability. As the CTAB/ethanol ratio is further increased, the pore size is reversely decreased, owing to the formation of solid microspheres. The non-destructive XRR measurement can evaluate the sub-nano pore sizes and its size distribution, which would fascinate the development and characterization of back-end of line process.

Proton-conducting composite membranes based on polybenzimidazole and sulfonated mesoporous organosilicate

Sulfonated mesoporous organosilicate (s-MPOs) was synthesized by the one-step sol–gel method as a novel inorganic additive derived for use in the fuel cell. TEM observations revealed that the s-MPOs has well-ordered structure and many SO3H groups on the inner surface of the mesopores. The s-MPOs was added to the proton-conductive polymer matrix, polybenzimidazole (PBI) in the presence of H3PO4, and the proton conductivities were measured at 60–100 °C under controlled humidity. The PBI composites filled with only 1 wt% of s-MPOs gave proton conductivity more than 10-times higher than the original PBI/H3PO4 membrane. The s-MPOs possessing many SO3H groups were able to form effective proton conductive pathways via its periodic structure and to improve the conductivity. The greatest conductivity was estimated to be 0.21 S cm−1 at 80 °C and 98 %RH in case of a PBI/s-MPOs20 (incl. approx. 20 mol% of the SO3H units in MPS) composite.

Amorphous TiO2coated into periodic mesoporous organosilicate channels as a new binary photocatalyst for regeneration of carbonyl compounds from oximes under sunlight irradiation

A new binary photocatalyst was easily prepared based on incorporation of amorphous titania into the periodic mesoporous organosilicate framework bearing photoresponsive isocyanurate species. The catalyst was found to be highly active in photocatalytic deoximation reaction under sunlight irradiation.

Molecular-level characterization of the structure and the surface chemistry of periodic mesoporous organosilicates using DNP-surface enhanced NMR spectroscopy

We present the molecular level characterization of a phenylpyridine-based periodic mesoporous organosilicate and its post-functionalized organometallic derivatives through the fast acquisition of high quality natural isotopic abundance 1D (13)C, (15)N, and (29)Si and 2D (1)H-(13)C and (1)H-(29)Si solid-state NMR spectra enhanced with dynamic nuclear polarization.

Poly(ethylene- co-vinyl alcohol)/sulfonated mesoporous organosilicate composites as proton-conductive membranes

Highly ordered mesoporous silica (MPS) and sulfonated mesoporous organosilicate (s-MPOs) were synthesized as novel inorganic additives derived for use in PEM-FCs, and were added to the non-protonic polymer matrix, poly(ethylene- co-vinyl alcohol) (EVOH). The proton conductivities of EVOH composites were measured at 50–100 °C under controlled high humidity values. The EVOH27 (ethylene content: 27 mol%) composite membranes filled with s-MPOs gave a proton conductivity more than 50-times higher than composites filled with simple treated MPS (t-MPS). The s-MPOs having many SO 3H groups was able to form effective proton conductive passages via its periodic structure and so improve conductivity in the polymer. We also investigated the temperature dependence of the conductivity for EVOH composites with ethylene content of 27 and 44 mol%. The EVOH44/s-MPOs composites had better conductivity than EVOH27 at higher temperatures. The greatest value was estimated to be 1.67 × 10 −3 S cm −1 without extra acid additives, at 80 °C and more than 96%RH.

Porphyrin-Embedded Silicate Materials for Detection of Hydrocarbon Solvents

The development of porphyrin-embedded mesoporous organosilicate materials for application to the detection of volatile hydrocarbon solvents is described. Design of the receptor and optical indicator construct begins with parallel selection of the porphyrin indicator and design of the mesoporous sorbent. For the porphyrin indicator, high binding affinity and strong changes in spectrophotometric character upon target interaction are desired. The sorbent should provide high target binding capacity and rapid binding kinetics. A number of porphyrin/metalloporphyrin variants and organosilicate sorbents were evaluated to determine the characteristics of their interaction with the targets, benzene, toluene, and hexane. The selected porphyrin candidates were covalently immobilized within a benzene-bridged sorbent. This construct was applied to the detection of targets using both fluorescence- and reflectance-based protocols. The use of red, green, and blue (RGB) color values from the constructs in a highly simplified detection scheme is described.

Functional and Functionalized Silicate Materials

ABSTRACTMesoporous organosilicate materials combine tunable binding characteristics, high surface area, and low materials density with an ordered pore network. Surface modifications provide the potential for incorporation of a variety of functional groups. We have taken advantage of these characteristics for the development of a range of materials to be utilized in various applications. In one approach, porphyrins are incorporated into the materials to provide unique catalytic properties. In these materials, the organosilicate scaffold stabilizes the porphyrin catalyst and facilitates interaction of the catalyst and target. Catalysis can be stimulated through exposure to light or application of an electrical current. The selectivity of the materials can be influenced through choice of organic bridging groups in the organosilicate structure and through selection of the porphyrin component. In addition, a type of molecular imprinting can be applied to provide sites on the pore walls that enhance adsorption selectivity for the target. These materials are directed at the development of self-decontaminating surfaces and coatings. Similar materials characteristics have been utilized in the development of solidphase extraction materials for use in the pre-concentration of nitroenergetic targets from ground and surface water samples. These materials are being incorporated into systems for in situ water quality monitoring. Mesoporous organosilicates can also be applied to the encapsulation of proteins and nucleic acids, stabilizing them for wider application of technologies utilizing these reagents. Modifications to the pore surfaces, in this case, are used to incorporate stabilizing agents such as sugars and proteins which should extend shelf-life and reduce storage restrictions.

Handed over

Chirality is directly transmitted from a monomer to a two-dimensional, ordered, mesoporous organosilicate material during its synthesis