Mesoporous Silica Material SBA-15 Research Articles

Synthesis of sustainable rice husk ash-derived nickel-decorated MCM-41 and SBA-15 mesoporous silica materials for hydrogen storage

To promote sustainability, it is essential to make use of biomass waste to create resources that can be transformed into mesoporous materials like silicates. These materials can be used as effective adsorbents for solid-state H2 storage systems. To meet the requirements of these systems, materials must be inexpensive, possess high specific surface areas, have proper pore arrangements, and exhibit reasonable H2 uptake. In this study, sustainable rice husk ash-derived MCM-41-RHA and SBA-15-RHA mesoporous silica materials were developed. These materials were engineered with different levels of Ni loading (2.5–10 wt%) and are used for H2 storage. The prepared MCM-41-RHA and SBA-15-RHA materials have a high BET-specific surface area of 1092.6 m2/g and 539.2 m2/g, respectively, with a mesopore distribution. The best results were observed for samples with a Ni loading of 5 wt%, such as MCM-41-RHA-Ni5 and SBA-15-RHA-Ni5, which demonstrated the highest H2 uptake of 3.64 wt% and 2.48 wt%, respectively, at 77 K and 1 bar. This was due to the strong interaction between the adsorbent and split over hydrogen despite the decrease in the BET-specific surface area after the incorporation of Ni. The enhanced interaction was evidenced by the increased isosteric heat of adsorption observed for MCM-41-RHA-Ni5 and SBA-15-RHA-Ni5, ranging from 21.1 to 8.1 kJ/mol, in contrast to the range of 6.9 to 4.1 kJ/mol for the pristine MCM-41-RHA and SBA-15-RHA. After five successive H2 uptake/release cycles, more than 92 % of the initial capacity was retained. This study presents a sustainable and cost-effective RHA-derived mesoporous silica material decorated with Ni- nanoparticles for solid-state H2 storage.

Probing the Morphology and Mobility of Amines in Porous Silica CO2 Sorbents by 1H T1–T2 Relaxation Correlation NMR

Molecular and oligomeric amines supported in porous oxide supports are a promising class of CO2 sorbent materials studied for CO2 removal from diverse streams such as flue gas and ambient air. Among the various amines investigated, low molecular weight, hyperbranched poly(ethyleneimine) (PEI), and tetraethylenepentamine (TEPA) are among the most extensively studied. While macroscopic structure–performance relationships relating the support structure, amine loading, and other factors affecting CO2 sorption capacities and kinetics have been developed, structural and dynamic information about the organic amine phase in the porous support is less plentiful. The structure and mobility of amines impregnated in the pores of porous supports directly impact gas sorption, as the accessibility of amine sites in the pores directly relates to amine distribution in the pores and overall pore filling as well as the dynamics of the amine chains. Here, we prepare a family of mesoporous silica SBA-15 materials containing varying loadings of oligomeric (PEI) and molecular (TEPA) amines. 1H T1–T2 relaxation correlation solid-state NMR experiments are used to characterize the structural and dynamic properties of the confined amines. Both TEPA and PEI are shown to form multiple different domains in the pores, each with distinguishable dynamic properties. TEPA and PEI form more rigid layers around the silica support walls at lower organic loading fractions, characterized by lower mobilities, followed by the formation of more mobile domains less engaged in pore wall interactions at higher loadings. TEPA shows faster mobilities than PEI because of its lower molecular weight. TEPA also appears to more easily transfer between domains within the pores, leading to generally faster CO2 uptake rates with higher sorption capacities, while PEI located closer to the pore walls remained much less mobile and is thus less engaged in CO2 capture.

Base modified organic mesoporous silicas, their characterization and application in the aldol reaction of n-butanal

Representative ordered mesoporous silica materials MCM-41 and SBA-15 were synthesized and modified with nitrogen-containing groups by grafting and co-condensation. The created catalytic centers strongly differ in basicity depending on the degree of substitution of the nitrogen atom. Furthermore, the introduced amount also depends on the structure of the modifier as shown by quantitative liquid phase 1H NMR. This allowed to calculate the turnover number in the aldol condensation of n-butanal which changed in the sequence: secondary > primary >> tertiary >> pyridinic basic centers. Corresponding reaction mechanisms considering the special structural features of the modifier are proposed.

Synergistic effect of amino-functionalized SBA-15 in Cu-catalyzed oxidative homocoupling of phenylacetylene

SBA-15 mesoporous silica materials with short mesochannels functionalized with various amino-groups, including NH2-, MeNH-, diamine-, triamine- and guanidine-groups were prepared through one-pot co-condensation of tetraethylorthosilicate (TEOS) and amino-containing trimethoxysilanes in the presence of P123 as pore-directing agent and an appropriate amount of Zr(IV) ions. The resultant materials immobilized with CuCl were examined as reusable catalysts in the oxidative homocoupling of phenylacetylene at room temperature with air as the oxidant. Efforts were made to avoid the liquid base additives. The Cu-guanidine-SBA-15 catalyst with Cu/guanidine molar ratio of 0.6 was found to satisfy this objective and gave the highest yield (up to ca. 97%) and nearly 100% selectivity of 1,4-diphenyl-1,3-butadiyne in 24 h. Moreover, the catalyst could retain around 90% yield after reuses for three times.

Adsorption and Catalytic Activity of Gold Nanoparticles in Mesoporous Silica: Effect of Pore Size and Dispersion Salinity.

The assembled state of nanoparticles (NPs) within porous matrices plays a governing role in directing their biological, electronic, and catalytic properties. However, the effects of the spatial confinement and environmental factors, such as salinity, on the NP assemblies within the pores are poorly understood. In this study, we use adsorption isotherms, spectrophotometry, and small-angle neutron scattering to develop a better understanding of the effect of spatial confinement on the assembled state and catalytic performance of gold (Au) NPs in propylamine-functionalized SBA-15 and MCM-41 mesoporous silica materials (mSiO2). We carry out a detailed investigation of the effect of pore diameter and ionic strength on the packing and spatial distribution of AuNPs within mSiO2 to get a comprehensive insight into the structure, functioning, and activity of these NPs. We demonstrate the ability of the adsorbed AuNPs to withstand aggregation under high salinity conditions. We attribute the observed preservation of the adsorbed state of AuNPs to the strong electrostatic attraction between oppositely charged pore walls and AuNPs. The preservation of the structure allows the AuNPs to retain their catalytic activity for a model reaction in high salinity aqueous solution, here, the reduction of p-nitrophenol to p-aminophenol, which otherwise is significantly diminished due to bulk aggregation of the AuNPs. This fundamental study demonstrates the critical role of confinement and dispersion salinity on the adsorption and catalytic performance of NPs.

Synthesis of SBA-Pr-NHC as a selective fluorescent sensor for the detection of Ag+ ion in aqueous media

SBA-Pr-NHC as a novel silica-based chemosensor was synthesized through the functionalization of mesoporous silica SBA-15 material with 4-hydroxy-2-oxo-2H-chromene-3-carbaldehyde, which was successfully immobilized to the surface of mesoporous silica, and its hexagonal mesoporous structure has been preserved. Photoluminescence spectroscopy was applied to study the sensing behavior of SBA-Pr-NHC, which displayed high selectivity for sensing Ag+ ion in aqueous media. After the addition of trace amounts of Ag+ ions into the aqueous solution, a significant enhancement of fluorescence emission has occurred with the detection limits of 2.4 × 10−5 M.

Preparation of SBA-15 and Zr-SBA-15 materials by direct-synthesis and pH-adjustment methods

SBA-15 mesoporous silica materials with zirconium atoms incorporated into its structure were prepared by two methods: direct-synthesis and pH-adjustment. Two nominal ratios of Zr/Si = 0 and 0.10 were evaluated. N2-physisorption, X-ray powder diffraction (XRPD) and, X-ray Photoelectron Spectroscopy (XPS) revealed that the morphology and structural order of the SBA-15 materials were greatly affected by the partial incorporation of zirconium into the SBA-15 structure as well as by the synthesis method. High-resolution transmission electron microscopy (HRTEM) of the materials prepared by pH-adjustment (SBA-15-2 and Zr-SBA-15-2 samples) revealed a more perfectly defined mesoporous structure with long-range ordering when compared with the materials obtained by direct-synthesis (SBA-15-1 and Zr-SBA-15-1 samples). The results by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Energy-Dispersion X-ray Spectroscopy (EDX) to evaluate the elemental composition of the materials indicated a better correlation using the pH-adjustment method.

Investigation of the silica pore size effect on the performance of polysulfone (PSf) mixed matrix membranes (MMMs) for gas separation

Abstract MCM-41 and SBA-15 mesoporous silica materials with different pore sizes (3.08 nm for small pore size MCM-41 (P 1), 5.89 nm for medium pore size SBA-15 (P 2), and 7.81 nm for large pore size SBA-15 (P 3)) were synthesized by the hydrothermal method and then functionalized with 3-aminopropyltrietoxysilane by postsynthesis treatments. Next, polysulfone-mesoporous silica mixed matrix membranes (MMMs) were prepared by the solution casting method. The obtained materials and MMMs were characterized by various techniques including X-ray diffraction, scanning electron microscopy, and N2 adsorption-desorption, and Brunauer-Emmett-Teller method to examine the crystallinity, morphology, and particle size, pore volume, specific surface area, and pore size distribution, respectively. Finally, the gas permeation rates of prepared MMMs were measured in 8 bar and 25 °C and the effect of pore size of modified and unmodified mesoporous silica on the gas separation performance of these MMMs were investigated. The experimental results indicate that the carbon dioxide (CO2) and methane (CH4) permeability and CO2/CH4 selectivity were increased with an enhancement in the particle pore size.

Catalytic transformation of ethanol to methane and butene over NiO NPs supported over mesoporous SBA-15

Hexagonally ordered mesoporous silica material SBA-15 with thick pore wall is an ideal catalytic support for immobilizing reactive tiny metal oxide nanoparticles (NPs) due to its large pore size, high specific surface area, excellent feasibility for the immobilization of NPs and robust nature of the mesoporous framework. [email protected] nanocomposite material has been synthesised through non-ionic surfactant assisted hydrothermal synthesis of SBA-15 followed by calcination, functionalization and impregnation. The material has been thoroughly characterized by using powder XRD, N2 sorption, XPS and NH3-TPD. [email protected] with ca. 13 % Ni(II) loading displayed specific surface area of 409 m2 g−1 and weak surface acidity. [email protected] showed good catalytic activity for conversion of ethanol to hydrocarbon fuels, specifically C1 and C4 hydrocarbons at 300 ̊C together with the production of hydrogen in almost stoichiometric amount. Further increase in the reaction temperature favoured cracking to yield methane as the major product. Supported NiO NPs acts as efficient catalytic centre for the conversion of ethanol to hydrocarbon fuels, which is an alternate to fossil fuel. Catalytic process is environment friendly and sustainable as the feedstock ethanol can be easily obtained from biomass resources.

Modulation of the Activity of Gold Clusters Immobilized on Functionalized Mesoporous Materials in the Oxidation of Cyclohexene via the Functional Group. The Case of Aminopropyl Moiety.

Gold nanoclusters and isolated gold atoms have been produced in a two-liquid phase procedure that involves a solution of gold in aqua regia and rosemary essential oil as organic layer. These gold entities have been immobilized on the ordered mesoporous silica material SBA-15 functionalized with different amounts of aminopropyl groups. The resulting materials have been characterized by XRD, N2 adsorption, chemical analysis, TGA, 29Si MAS NMR, 13C CP/MAS NMR, UV-vis spectroscopy, XPS, and STEM. The Au-containing materials retain the ordering and porosity of the pristine support. Gold content varies in the range of 0.07–0.7 wt% as a function of the specific immobilization conditions, while STEM evidences the presence of isolated gold atoms. XPS shows a shift of the Au 4f BE toward values lower than those of metallic gold. The catalytic activity in the oxidation of cyclohexene with molecular oxygen at atmospheric pressure parallels the Au content of the aminopropyl-SBA-15 supports. This activity is higher than that of analogous Au entities immobilized on SBA-15 functionalized with thiol or sulfonate groups, the activity decreasing in the order Au-NH2 > Au-SO3− > Au-SH. This behavior has been attributed to differences in the interaction strength between the functional group and the Au entities, which is optimum for the aminopropyl groups.

Microwave-synthesized high-performance mesoporous SBA-15 silica materials for CO2 capture

Microwave-assisted post-synthetic detemplating method was applied to remove successfully the occluded organic template from the mesoporous silica frameworks of as-synthesized SBA-15 within a short period of time compared to a conventional method, such as furnace calcination. The nitrogen adsorption/desorption isotherm studies showed that the resultant detemplated SBA-15 had a very high specific surface area of 1,271 m2/g, large pore size of 9.21 nm and high pore volume of 2.10 cm3/g; while the powder X-ray diffraction patterns and high-resolution TEM images of these support materials revealed the presence of highly ordered mesopores without any structural shrinkage. Both the microwave power and time during post-synthetic microwave irradiation were found to influence the morphological structure of the SBA-15 support. To evaluate the adsorption performance of the microwave-irradiated SBA-15 support, CO2 adsorption uptake was measured after functionalizing it with different loadings of polyethyleneimine (PEI) under 9.7% CO2/N2 mixture at 75oC. The maximum CO2 uptake was 3.63 mmol CO2/g (0.16 g/g), with an optimum PEI loading of 70 wt%. Because of the significant improvement in structural characteristics, the microwave-irradiated SBA-15 supports facilitated more PEI incorporation that contributed to about 15% higher CO2 uptake than that of conventional furnace calcined one. In addition, the sorbent demonstrated very good cyclic stability when tested over 25 cycles and for a total duration of 20 h in humid conditions.

Tetranuclear Zn complex covalently immobilized on sulfopropylsilylated mesoporous silica: An efficient catalyst for ring opening reaction of epoxide with amine

Tetranuclear Zn complex, [Zn4(L)2(LH)2((CH3)2SO)2]·2CH3OH·(CH3)2SO·H2O (1) [where LH3 = 3-(E)-(2-hydroxyphenylimino)methyl-4-hydroxy-5-hydroxymethylphenyl (LH3)] was prepared and characterized by single-crystal X-ray analysis. Then, it was incorporated to the sulfopropylsilylated MCM-48, MCM-41 and SBA-15 mesoporous silica materials. The prepared materials were thoroughly characterized by XRD, FT-IR, N2 adsorption/desorption analysis, NH3-TPD, TGA, SEM-EDX and ICP-OES measurements. These catalysts were successfully used for the ring opening reaction of propylene oxide with morpholine producing the corresponding β-aminoalcohols. An abrupt increase in catalytic activities was observed after anchoring of the tetranuclear Zn complex onto the inner surface of sulfopropylsilylated mesoporous materials. Among all the catalysts, the tetranuclear Zn complex incorporated MCM-48 was found to be most active in this reaction system and gave maximum 95% conversion. Catalysis by the tetranuclear Zn complex immobilized on MCM-48 was totally heterogeneous and the catalyst was recyclable up to 4 times without leaching.

Exploring the possibilities of carbon materials as catalytic supports for partial oxidation reactions

The present study evaluates the possibilities as catalytic supports for partial oxidation reactions of two activated carbons obtained from biomass waste by partial gasification with CO2 and chemical activation with H3PO4 (AC and ACP, respectively), and of one mesostructured carbon material (PMC). For comparative purposes, the results are compared with those obtained with conventional mesoporous silica material SBA-15. The porous structure and chemical composition have been evaluated by N2 and CO2 adsorption at -196 and 0 °C respectively, SEM, TEM, ICP, XRD and TPR, whereas the support properties have been evaluated as support for Cu active phases during propylene partial oxidation reaction. The results have shown that ACP is a very useful catalytic support that presents many advantages, due to its low cost and simple synthesis, that allow preparing activated carbons with high mesoporosity, favoring the distribution of Cu species, with high stability against gasification at relatively high temperatures and good catalytic activity and selectivity in acrolein production.

Mesoporous silica induces hippocampal neurons cell autophagy through AMPK/mTOR/P70S6K signaling pathway.

Mesoporous silica is a drug carrier with strong targeting, large loading capacity, and easy modification of its surface while its toxicity draws increasing attention recently. In this study, we evaluated the impact of SBA-15 nanomaterials on hippocampal neurons. We found that SBA-15 induces oxidative damage to hippocampal neurons HT22, which further activates autophagy. Treatment with the mammalian target of rapamycin (mTOR) inhibitor AZD8055, the phosphorylation level of mTOR and P70S6K reduced and increased levels of p-AMPK meaning that the adenosine-activated protein kinase (AMPK)/mTOR/P70S6K pathway is involved in SBA-15 induced autophagy of HT22. These results suggested that mesoporous silica material SBA-15 might affect central nervous cells via oxidative stress activation of the AMPK/mTOR/P70S6K pathway, which provides a theoretical basis for safe administration of such materials in patients.

A support effect on the hydrodeoxygenation reaction of anisole by ruthenium catalysts

Abstract Ordered mesoporous silica materials SBA-15, SBA-16 and MCM-41 were synthesized and used as supports for the active phase which was made of ruthenium nanoparticles. The physicochemical properties of the systems were characterized by XRD, N2 sorption and TEM. The systems were used as catalysts of hydrodeoxygenation of anisole, carried out in temperatures from the range 90–130 °C under hydrogen pressure of 6 MPa. The impact of two variables (i) temperature and (ii) type of support on the course of the reaction was checked. The main product of the reaction catalysed by MCM-41/Ru was toluene, while if the support was either SBA-15/Ru or SBA-16/Ru, the main product was methoxycyclohexane. In the reaction conditions applied, 100% of anisole conversion was achieved.

Detailed investigation on properties of novel commercial mesoporous silica materials

A detailed investigation on the main characteristics was conducted on a novel and unique group of industrially produced mesoporous silica material. Six materials from a TMPS group were selected in the respect to their pore size ranging from 1.8 nm up to 4.2 nm. Four of the selected samples were also made with silica doping making them potentially attractive for water adsorption applications with the advantage of the pore-tuning possibilities for specific use. The surface area, pore volume and pore size distribution of these materials were established by standard nitrogen adsorption at T = 77.4 K showing typical values of mesoporous silica materials such as high surface area in the range from 600 to 750 m 2 g −1 and pore volumes reaching 0.38 cm 3 g −1 in the case of the smallest TMPS-1.5A and 0.98 cm 3 g −1 in the case of the largest TMPS-4R. The wall thickness was found out regular around 1.5 ~ 2 nm with lower values attributed to bigger pore sized samples promising good structural integrity. Specific heat showed regular values through all the samples at ~ 0.85 J g −1 K −1 . Additional information on the structural characteristics and the effect on the amount of silanol group presence and the difference on regular and aluminium-doped samples were studied by means of 29 Si DD/MAS NMR. Additionally, elemental analysis by EDS was conducted as well. All the characteristics of the TMPS materials were compared to the standard mesoporous silica materials SBA-15 and MCM-41. • Bulk produced aluminium-doped mesoporous silica materials. • Variable pore size from 1.5 nm to 7 nm, typically. • High thermal stability and low pore size distribution. • Typical hexagonal structure and spherical particle cells size of 50–200 nm. • High water adsorption and hydrophilic properties of Al-doped samples.

Synthesis and characterization of mesoporous materials as a carrier and release of prednisolone in drug delivery system

The mesoporous silica SBA-15 material was synthesized as a carrier in drug delivery system (DDS). The Prepared mesoporous material SBA-15 was characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and N2 adsorption/desorption isotherm, Fourier transform infrared (FTIR) spectroscopy and Thermal Gravimetric Analysis (TGA). The drug loading efficiency (DLE) was investigated and found that the maximum drug loading efficiency was (37.2%). The drug release behavior of Prednisolone (PRD) was performed in three different media at body temperature 37 °C such as; distilled water at pH 6.8, phosphate buffer solution (PBS) at pH 6.8 and according to United State Pharmacopeia (USP38) in PBS media at pH 7.4. The results were found that maximum release could reach up to 86.29% at pH 7.4 after 24 h. Different kinetic release models such as first order, Korsmeyer-Peppas, Hixsone-Crowell, Higuchi, and Weibull were applied. The drug release data was fitted with Kosmeyer–Peppas model after 24h and follow non-Fickian diffusion for distilled water media of pH 6.8, n = 0.5387 with determination coefficient (R2) 0.9178 and follow Fickian diffusion for both PBS media of pH 6.8, n = 0.451 and pH 7.4, n = 0.465 with R2 0.9871 and 0.9826 respectively.

Silica Mesoporous Materials -an Efficient Sorbent for Wine Polyphenols Separation

Highly ordered-pore SBA-15 was synthesized by co-condensation of tetraethylorthosilicate (TEOS) and 3-aminopropyltriethoxysilane (APTES) using an amphiphilic block copolymer as structure-directing agent. The BET, EDX, TGA-DSC and SEM analysis have been used for sorbent characterization. The adsorption properties of the calcined mesoporous silica SBA-15 material appears to be a consequence of the silanol groups presence that are active sites for adsorption, were evaluated in the clarification process of two types of red wines. The purpose of this study was the investigation of the total polyphenols content (reduction), the selectivity and stabilization for some compounds (phenolic acids, epicatechin, and catechin) and the chromatic characteristics of wine. HPLC chromatograms exhibit the retention of quercetin and trans-resveratrol, catechin, epicatechin, rutin, and phenolic acids. The decrease in the polyphenolic compounds content in red wines avoids the oxidative browning process without modification of wine color. Due to their beneficial to human health thanks to antioxidative, antiinflamatory, antiviral, cardioprotective, anticarcinogenic and antimutagenic properties the polyphenolic extract might prove interesting as pharmaconutrients or as dietary sources.

Hydrodeoxygenation of Bio-Derived Phenol to Cyclohexane Fuel Catalyzed by Bifunctional Mesoporous Organic-Inorganic Hybrids.

In this work, mesoporous silica materials SBA-15 functionalized with propyl/ phenyl-sulfonic acid group were synthesized and loaded with Pt to form bifunctional catalysts. SAXRD, WAXRD, N2 adsorption-desorption, TEM techniques were used to characterize the above bifunctional catalysts. These bifunctional catalysts were applied to the reaction of hydrodeoxygenation (HDO) of bio-derived phenol (PhOH) to produce cyclohexane fuel and showed very good catalytic performances. There were strong synergies between the metal sites and the acid sites on the bifunctional catalysts. This reaction of phenol HDO provides a model system for the catalytic upgrading of biomass-derived fuel.

Efficient Synthesis and Antimicrobial Evaluation of Pyrazolopyranopyrimidines in the Presence of SBA-Pr-SO3H as a Nanoporous Acid Catalyst.

A simple, efficient, and environmentally friendly method has been developed for the synthesis of a series of tricyclic fused pyrazolopyranopyrimidines via a one-pot three-component reaction of barbituric acids, aromatic aldehydes, and 3-methyl-5-pyrazolone in the presence of SBA-Pr-SO3H. SBA-15 mesoporous silica material functionalized with propyl sulfonic acid groups was used as a heterogeneous Brønsted acid catalyst with hexagonal structure, high surface area, thick walls, and large uniform pores. All reactions were performed under reflux conditions in water in the presence of a catalytic amount of SBA-Pr-SO3H. High yields, mild reaction conditions, short reaction times, and simple work-up procedures are some advantages of this method. The antimicrobial activities of the synthesized compounds were also evaluated and some products exhibited significant antibacterial activities at low concentrations.