Channels Of Mesoporous SBA-15 Research Articles

Copper nanoparticles decorated N-doped mesoporous carbon with bimodal pores for selective gas separation and energy storage applications

• Mesoporous N & Cu doped carbon materials with enhanced physico-chemical features. • Materials display redox, conducting, basic, adsorption and porous characteristics. • N/Cu doped carons show ordered structure with a bimodal pores size distribution. • High gas adsorption capacity and selectivity in a mixture of CO 2 /H 2 and CO 2 /CH 4. • High values for supercapacitance with good cyclic ability and capacitance retention. We demonstrate a synthesis of copper nanoparticles decorated over nitrogen-doped mesoporous carbon with different N and Cu contents which exhibit conducting, redox, basic, adsorption, and excellent textural properties. These materials are prepared through a nanotemplating approach by simultaneously encapsulating sucrose, guanidine hydrochloride, and Cu(NO 3 ) 2 into the porous channels of mesoporous SBA-15 at a low carbonization temperature of 600 °C. The prepared materials exhibit an ordered mesoporous carbon framework with bimodal pores, decorated with nitrogen and Cu functionalities on the surface of the pores and in the wall structure. The presence of nitrogen functionalities in the porous carbon matrix not only helps to reduce the Cu ions but also stabilizes the nanoparticles and offers redox sites, which are beneficial for adsorption and electrochemical applications. The optimized sample exhibits the highest adsorption capacity of different gases such as CO 2 – 22.5 mmol/g at 273 K, H 2 −13.5 mmol/g at 77 K at 30 bar and CH 4 − 5 mmol/g at 298 K and 50 bar. We also demonstrate that the prepared material shows a high selectivity of adsorption towards CO 2 in a mixture of CO 2 /H 2 and CO 2 /CH 4 and it also registers a high supercapacitance of 209 F g −1 at a current density of 1 A g −1 with excellent cyclic stability.

Effects of spatially confined nickel nanoparticles in surface-pretreated hydrophobic SBA-15 for dry reforming of CH4 with CO2

The efficient methods to preserve original smaller nickel nanoparticles (NP) with its even size distribution of ∼5 nm on a highly ordered mesoporous SBA-15 (NP/SBA-15) were investigated for a high temperature (800 °C) dry reforming of methane with CO2 (DRM). The suppressed thermal aggregation with less coke deposition and higher catalytic activity were observed by the confined nickel nanoparticles spatially in the mesoporous SBA-15 channels. Especially, two-step surface-pretreated SBA-15 with acetic anhydride followed by successive H2O treatment showed a higher dispersion of organics-stabilized nickel nanoparticles, which were preferentially deposited in the ordered mesoporous inner SBA-15 channels with its insignificant aggregation. On the optimal NP(10)/SBA-15 with 10 wt%Ni possessing the characteristics of the hydrophobic SBA-15 inner surfaces, as-prepared nickel nanoparticles were selectively and homogeneously distributed in the inner mesoporous SBA-15 channels with its small depositions on the outer SBA-15 surfaces. The spatial confinement effects were realized due to the less mobility of the smaller nickel nanoparticles by keeping its original particle sizes even after a long-term DRM reaction at 800 °C for 120 h. The phenomena were responsible for an enhanced catalytic stability by suppressing a severe sintering of nanoparticles and less coke formation even under a harsh DRM reaction condition.

Dual Stimuli-Responsive Copper Nanoparticles Decorated SBA-15: A Highly Efficient Catalyst for the Oxidation of Alcohols in Water

In the present work, a temperature and pH-responsive hybrid catalytic system using copolymer-capped mesoporous silica particles with metal nanoparticles is proposed. The poly(2-(dimethylamino)ethyl methacrylate)(DMAEMA)-co-N-tert-butyl acrylamide) (TBA)) shell on mesoporous silica SBA-15 was obtained through free radical polymerization. Then, copper nanoparticles (CuNPs) decorated SBA-15/copolymer hybrid materials were synthesized using the NaBH4 reduction method. SBA-15 was functionalized with trimethoxylsilylpropyl methacrylate (TMSPM) and named TSBA. It was found that the CuNPs were uniformly dispersed in the mesoporous channels of SBA-15, and the hybrid catalyst exhibited excellent catalytic performance for the selective oxidation of different substituted benzyl alcohols in water using H2O2 as an oxidant at room temperature. The dual (temperature and pH-) responsive behaviors of the CuNPs/p(DMAEMA-co-TBA)/TSBA catalyst were investigated using the dynamic light scattering technique. The conversion of catalytic products and selectivity were calculated using gas chromatographic techniques, whereas the molecular structure of the products was identified using 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The catalyst showed excellent catalytic activity toward the oxidation of alcohol to aldehyde in an aqueous medium below the lower critical solution temperature (LCST) and pKa values (7–7.5) of the copolymer. The main advantages of the hybrid catalyst, as compared to the existing catalysts, are outstanding alcohol conversion (up to 99%) for a short reaction time (1 h), small amount of the catalyst (5 mg), and good recyclability equal to at least five times.

Comparison in thermal stability and catalytic performance of H4PMo11VO40 heteropolyacid supported on mesoporous and macroporous silica materials

Ordered mesoporous silica, SBA-15 and MCM-41, and three-dimensionally ordered macroporous SiO2 were used as the supports of H4PMo11VO40 heteropolyacid for methacrolein oxidation. The dispersion and structural evolutions of the heteropolyacid along with thermal treatment were investigated. It was found that the heteropolyacid entered the one-dimensional mesoporous channels of SBA-15 and MCM-41, and the crystallization and growth were limited, leading to high dispersion of the heteropolyacid. However, the thermal stability was decreased under high dispersion. The migration of the heteropolyacid was observed to the end of the one-dimensional channels of SBA-15 and the outer surface of MCM-41 with calcination, accompanied by the decomposition of the heteropolyacid and the formation of MoO3. In comparison, the crystallization and growth of heteropolyacid were not limited in the open macropores of three-dimensionally ordered macroporous SiO2. Dispersed particles on the surface of the macropores with size of about 5 nm exhibited a higher thermal stability. The decomposition of the heteropolyacid in the SBA-15 and MCM-41 supported catalysts resulted in the loss of strong acid sites, causing low selectivity to methacrylic acid in methacrolein oxidation. High thermal stability with high exposure of the active sites in the three-dimensionally ordered macroporous SiO2 supported catalyst contributed to the enhancement in the catalytic performance.

Novel hybrid materials based on heteroleptic Ru(III) complexes immobilized on SBA-15 mesoporous silica as highly potent antimicrobial and cytotoxic agents

Three novel hybrid materials, SBA-15-RuValen, SBA-15-RuValpnol, and SBA-15-RuValdiamci, were obtained by immobilization of new [Ru(L)(PPh3)Cl] complexes (H2L = H2Valen, H2Valpnol, H2Valdiamci, are Schiff base proligands obtained by condensation of o-vanillin with ethylenediamine, 1,3-diamino-2-propanol, and 1,2-diaminocyclohexane, respectively) inside the mesoporous channels of SBA-15. [Ru(Valen)(PPh3)Cl]·3H2O (RuValen), [Ru(Valpnol)(PPh3)Cl]·3H2O (RuValpnol), and [Ru(Valdiamci)(PPh3)Cl]·4H2O (RuValdiamci) complexes were characterized by microanalysis (C,H,N), IR and UV–Vis spectroscopy, magnetic measurements. The structure of RuValen was also confirmed by single crystal X-ray diffraction. The hybrid materials were thoroughly characterized in terms of structure, composition, morphology, and textural properties. The results indicate the uniform distribution of Ru(III) complexes on the internal surface of SBA-15, the immobilization process having no significant influence on the structure of the support. The novel hybrid materials demonstrated high antibacterial and anti-biofilm activity against Enterococcus faecalis, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. In vitro tests regarding the cytotoxic effect on adenocarcinoma (HeLa) cells showed that all three hybrid materials decreased the cell viability in a dose-dependent manner, being very promising for medical applications.

Nitrogen-doped carbon dots encapsulated in the mesoporous channels of SBA-15 with solid-state fluorescence and excellent stability.

A simple and low-cost approach is developed, by which nitrogen-doped carbon dots (NCDs) with a negative potential are assembled inside the mesoporous channels of SBA-15 via capillary force. The unique confined microenvironment leads to a strong interaction between confined NCDs and the inner surface of SBA-15, thus effectively avoiding the aggregation of NCDs. The resultant composite (NCDs-in-SBA-15) exhibits blue fluorescence similar to the NCD aqueous solution, and shows excellent structural, thermal and photostability. Solid NCDs-in-SBA-15 still emits fluorescence even after heat treatment at 400 °C under ambient atmosphere. In addition, NCDs-in-SBA-15 possesses remarkable resistance to acid/alkali solvents. Furthermore, NCDs-in-SBA-15 shows superior selectivity and adsorption capacity to Fe3+. The facile approach and these advantageous performances could make CDs meet the requirements of fluorescent materials in the solid state and then have wider applications.

Molecular assembly and photoluminescence of lanthanide/silicon[sbnd]oxygen network/poly-vinylphenylboronic functionalized SBA-15 hybrids

Novel organic-inorganic mesoporous luminescent polymeric composite materials containing lanthanide (Eu3+, Tb3+) complexes covalently bonded to mesoporous silica have been prepared in situ, followed by the polymerization reaction of the monomer 4-vinylphenylboronic acid (VPBA) extending along the mesoporous SBA-15 channels. The obtained materials were investigated by Fourier transform infrared spectroscopy (FT-IR), Ultraviolet absorption spectra (UV), X-ray diffraction (SAXRD), N2 adsorption/desorption isotherms, Transmission electron microscopy (TEM), thermogravimetry (TG), and luminescence spectroscopy in detail. These characterizations have proved that composite materials possess high surface area, uniform mesoporous structure, good crystallization and relatively excellent luminescence properties. The terminal ligand phen was used to investigate the difference of photo physical and luminescent properties between binary and ternary composite materials. Furthermore, the results have revealed that the composite material Eu(PVPBA-S15)3phen showed more efficient intramolecular energy transfer between the europium ion and the ligands, and more excellent characteristic emission of the europium ion under UV irradiation with higher 5D0 luminescence quantum efficiency than the composite materials Eu(PVPBA-S15)3 without phen. The excellent luminescence properties and ordered mesoporous structures could give rise to many potential applications in optical and electronic areas.

Confinement of iPP crystallites within mesoporous SBA-15 channels in extruded iPP-SBA-15 nanocomposites studied by Small Angle X-ray scattering

The main objective of this research is the study of different nanocomposites based on isotactic polypropylene (iPP) and mesoporous SBA-15 silica prepared by melt extrusion, analyzing the possible effect of this filler on the polymorphic behavior of iPP and the eventual observation of confinement effects. Thus, simultaneous Small Angle X-ray Scattering/Wide Angle X-ray Diffraction (SAXS/WAXD) synchrotron experiments at variable temperature have been performed on several iPP nanocomposites with different contents of SBA-15 mesoporous particles. Real-time variable-temperature SAXS measurements turned out a very useful tool to analyze the confinement of iPP crystallites within SBA-15 channels, and also to determine the most probable long spacing of chains located outside the SBA-15 nanospaces. Importance of these structural features is assessed by changes in the mechanical response of the final materials, finding that the presence of mesoporous particles leads to a reinforcing effect and contribute to improve the final dimensional stability.

Glucose-Assisted Preparation of a Nickel–Molybdenum Carbide Bimetallic Catalyst for Chemoselective Hydrogenation of Nitroaromatics and Hydrodeoxygenation of m-Cresol

Developing a safe, facile, clean, low-cost, and scalable new method to replace the conventional methane reductive carburization process for preparing carbon-nanotube, coverage-free, highly dispersed, metal carbide based bimetallic catalysts without a sacrificial metal loading is of great significance but remains a challenge. In this work, we develop a facile and robust strategy for successfully preparing a highly dispersed supported nickel–molybdenum carbide (NiMo2C) bimetallic catalyst on mesoporous silica [NiMo2C/SBA-15(Glu.)], in which the renewable glucose is employed to serve as an assisting agent for high metal dispersion within the mesoporous channels of SBA-15 in the impregnation process and as a carbon source to replace flammable methane for metal carbide formation through a reductive carburization process. From diverse characterization results, the as-prepared NiMo2C/SBA-15(Glu.) catalyst demonstrates a much higher metal dispersion (ca. 4.1 nm in this work vs ca. 80 nm aggregates by the conventi...

Saponin-loaded SBA-15: release properties and cytotoxicity to Panc-I cancer cells

In this study, first time a nanoformulation, saponin-loaded SBA-15 has been developed for an improved and continuous release. The SBA-15 nanopowder was synthesized by a hydrothermal process. Saponin was introduced into the mesoporous channels of SBA-15 and its concentration in SBA-15 was measured by UV–visible spectrophotometry. The pristine SBA-15 and saponin-loaded SBA-15 were characterized by small-angle XRD, FESEM, HRTEM, TGA, FTIR. N2 adsorption–desorption isotherms were used to measure the specific surface area and pore channel structure parameters of pristine and loaded SBA-15. Saponin release was studied in phosphate buffered saline (pH 7.4), which revealed that the release rate could be effectively controlled. The controlled drug release is highly desired for cancer treatment. The cytotoxicity of pristine and loaded SBA-15 was analyzed on Panc-I cancer cells. Both the pristine SBA-15 and saponin-loaded SBA-15 nanoparticles showed specific toxicity on the cancer cells. The preliminary results showed that saponin-loaded SBA-15 could be an effective therapeutic agent for Panc-I cancer cells.

Nickel Particles Selectively Confined in the Mesoporous Channels of SBA-15 Yielding a Very Stable Catalyst for DRM Reaction

A series of four Ni catalysts supported on SBA-15 and on a high SiO2 surface area have been prepared by modified impregnation (ImU) and deposition-precipitation (DP) methods. The catalysts have been extensively characterized, including in situ XAS (bulk sensitive) and XPS (surface sensitive) techniques, and their catalytic activities evaluated in the dry reforming reaction of methane (DRM). The combined use of XPS and XAS has allowed us to determine the location of nickel particles on each catalyst after reduction at high temperature (750 °C). Both Ni/SiO2-DP and Ni/SBA-15-DP catalysts yield well-dispersed and homogeneous metallic phases mainly located in the mesoporosity of both supports. On the contrary, the Ni/SiO2-ImU and Ni/SBA-15-ImU catalysts present a bimodal distribution of the reduced nickel phase, with nickel metallic particles located out and into the mesoporous structure of SiO2 or the SBA-15 channels. The Ni/SBA-15-DP catalyst was found the most stable and performing system, with a very low level of carbon deposition, about an order of magnitude lower than the equivalent ImU catalyst. This outstanding performance comes from the confinement of small and homogeneous nickel particles in the mesoporous channels of SBA-15, which, in strong interaction with the support, are resistant to sintering and coke deposition during the demanding reaction conditions of DRM.

Performance of 1,8-Diazabicyclo[5.4.0]undec-7-ene-Modified SBA-15 for Selective Adsorption of CO2

In this work, SBA-15-(DBU-X) was prepared by dipping 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) into the mesoporous channels of SBA-15 in an attempt to improve the CO2 adsorption. The synthesized SBA-15-(DBU-X) was characterized with scanning electron microscopy, thermogravimetric analysis, Brunauer–Emmett–Teller adsorption analysis, and other methods. Then the CO2 adsorption/desorption properties were investigated using a self-designed fixed-bed adsorption system. The results indicated that DBU could be loaded on the SBA-15 mesoporous molecular sieves effectively and that SBA-15-(DBU-X) had good adsorption capacity toward CO2. SBA-15-(DBU-X) had good thermal stability at temperatures below 140 °C. At room temperature, with increasing loading of DBU and total flow rate of simulated flue gas, the adsorption of CO2 on SBA-15-(DBU-X) had an increasing trend followed by a decrease. When the volume fraction ratio of CO2 and H2O was 1:1 in the simulated flue gas, SBA-15-(DBU-X) had an optimum capacity of CO2 adso...

Highly dispersed nickel within mesochannels of SBA-15 for CO methanation with enhanced activity and excellent thermostability

In this work, several nickel-based SBA-15 catalysts were prepared by surfactant-assisted impregnation method and applied in CO methanation reaction. The characterization results showed that Ni species were uniformly distributed in the ordered mesoporous channels of SBA-15 by adding proper surfactants. The morphologies of the unroasted catalysts and spent catalysts after 100h stability test were also investigated. The surfactant can hinder the migration of metal ions during drying and inhibit the aggregation of NiO during calcination, which ultimately improve the nickel dispersion. Consequently, the Ni/SBA-15 catalysts prepared with surfactant-assisted impregnation method exhibited superior activity and excellent thermostability owing to the moderate interaction between nickel and support, high nickel surface area and the confinement of support. The 10%Ni/S15(3) catalyst achieved the best activity with 100% CO conversion and about 99.9% CH4 yield at 350°C, 0.3MPa and 15,000mL/g/h.

Fabricating hydrophobic nanoparticles within mesoporous channel of silica for efficient TSNA removal

Based on the synthesis of super hydrophobic silicic xerogel (SG) from methyltrimethoxysilane (MTMS) and dimethyldimethoxysilane (DMDMS), siliceous hydrophobic nanoparticles were fabricated within the mesoporous channels of SBA-15, in order to enhance the efficiency of adsorbing tobacco specific N-nitrosamines (TSNA) in aqueous solution. The concentration of precursor solution was adjusted to master the distribution of hydrophobic particles and the mean hydrophobicity of resulting composite, 150% increasing the capacity of SBA-15 in liquid adsorption of TSNA.

The selective hydrogenation of rosin to hydroabietic content using Pd/SBA-15 as catalysts

Well-dispersed Pd particles supported on ordered mesoporous SBA-15 were synthesized by the incipient wetness impregnation of SBA-15 with PdCl2 as precursor. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption–desorption isotherms, inductively couple plasma atomic emission spectrometry (ICP-AES), and there was revealed an excellent dispersion of Pd nanoparticles in the mesoporous SBA-15 channels. Furthermore, Pd/SBA-15 mesoporous material was used as catalyst for hydrogenation of rosin and exhibited a highly catalytic activity and reusability at least after five recycles.

Oxidation of styrene to benzaldehyde with hydrogen peroxide in the presence of catalysts obtained by the immobilization of H3PW12O40 on SBA-15 mesoporous material

Mesoporous SBA-15 functionalized catalysts with controllable H3PW12O40 loadings were prepared using a one-step co-condensation method and used for the oxidation of styrene to benzaldehyde with hydrogen peroxide as the oxidant. These catalysts were well characterized by Fourier transform infrared spectroscopy, Raman scattering spectroscopy, low angle X-ray diffraction, wide angle X-ray diffraction, scanning electronic microscopy, transmission electron microscopy and N2 adsorption–desorption. The results showed that H3PW12O40 was successfully incorporated into the mesoporous channels of SBA-15, which increased the specific surface area of the active components. These catalysts were applied to catalyze styrene oxidation in the presence of cheap and green hydrogen peroxide, and the key reaction parameters including H3PW12O40 loading, reaction temperature, solvent, H2O2 amount, and reaction time on the catalytic performance were investigated. The heterogeneous H3PW12O40-catalyzed styrene oxidations showed the oxidation product was benzaldehyde as the only product. This route showed green and simple property.

Fine CuO anisotropic nanoparticles supported on mesoporous SBA-15 for selective hydrogenation of nitroaromatics

SBA-15 modified with APTMS (3-aminopropyl trimethoxysilane) having pore diameter (∼8nm) has been synthesized and impregnated with 1–10wt.% Cu using Cu(NO3)2 as a metal source followed by calcination at 350°C. As-prepared CuO/ap-SBA-15 powder showed changes in the color from white for bare SBA-15 to light green due to formation of anisotropic CuO nanoparticles that exhibited a characteristic plasmon absorption band at 359 and 747nm. TEM studies showed a change in the morphology of CuO NPs as a function of increased Cu loading. Moreover, well dispersed CuO nanospheres (∼5–6nm) and nanorods (aspect ratio ∼11–20nm) having monoclinic crystal phase were observed within the mesoporous channels of SBA-15. Elemental mapping studies confirmed uniform distribution of CuO nanoparticles on the surface of SBA-15. An increase in surface area was also observed from 694m2g−1 for SBA-15 to 762m2g−1 for 10wt.% Cu loading probably due to the deposition of excess of CuO nanoparticles on the outer siliceous surface. The catalytic activity also increased with Cu loading and 10wt.% CuO/ap-SBA-15 catalyst displayed the highest catalytic activity for the reduction of m-chloronitrobenzene and m-nitrotoluene with 83% and 100% selectivity for m-chloroaniline and m-aminotoluene respectively.

Epoxidation of olefins with oxygen/isobutyraldehyde over transition-metal-substituted phosphomolybdic acid on SBA-15

A series of polyoxometalate-based heterogeneous catalysts were prepared by immobilized transition metal mono-substituted phosphomolybdic acids (PMo11M, M=Fe, Co or Cu) or unsubstituted phosphomolybdic acid (PMo12) on amino-functionalized SBA-15. A variety of characterization results demonstrated that the PMo11M units are uniformly dispersed on the surface or in the channels of mesoporous SBA-15. The catalytic properties of these hybrid materials (denoted as PMo11M/SBA or PMo12/SBA) were investigated in the epoxidation of olefins with molecular oxygen as oxidant and isobutyraldehyde as co-reagent. It has been found that PMo11Co/SBA and PMo11Cu/SBA are catalytically active for the epoxidation of cyclooctene with acetonitrile as solvent, while PMo11Fe/SBA and PMo12/SBA are nearly inactive under the same reaction conditions. Moreover, the relatively active PMo11Co/SBA catalyst could also efficiently convert cyclohexene and 1-octene to the corresponding epoxides, and its catalytic activity was solvent dependent. Using suitable solvent like acetonitrile could efficiently inhibit the deactivation of the catalyst, thus bringing excellent stability and recyclability for the PMo11Co/SBA catalyst.

Synthesis and Heterogenization of Siloxane Functionalized Cobalt Complex: Potential Catalyst for Oxidation of Alcohols

Cobalticinium complex containing siloxane moiety on ligand center was first time synthesized, characterized and heterogenized on the surface of SBA-15 molecular sieves. FT-IR and 29Si-MAS-NMR spectrum evidence the successful grafting of the cobalt complex on the surface of SBA-15. N2 sorption isotherm of cobalticinium complex grafted sample showed the decrease in surface area, pore volume, further confirms the presence of complex inside the channel of mesoporous SBA-15. The heterogenized complex exhibited promising activity for oxidation of alcohols with good selectivity of ketone. Further the catalytic activity remains intact after two recycles. Cobalticinium complex possessing siloxane functionality was prepared first time and heterogenized on SBA-15 surface. The resultant materials showed as promising recyclable heterogeneous catalyst for oxidation of alcohols.

The role of oxide location in HMF etherification with ethanol over sulfated ZrO2 supported on SBA-15

The etherification of 5-hydroxymethyl-2-furfural (HMF) over ZrO2 and sulfated ZrO2-SBA-15 was chosen as a case study to analyze (i) the quantitative relationship between the concentration of Lewis and Brønsted acid sites and the catalytic behavior in the above reaction, which is also of industrial relevance for the production of biodiesel additives, and (ii) how the location of zirconia nanoparticles inside or outside the mesoporous channels of SBA-15 could significantly influence the specific reactivity in this reaction, both before and after sulfation. Depending on the loading of zirconia (about 10 or 35wt%), the characterization data by different techniques (TEM, XRD, BET, Dr-UV–vis, and XPS) agree in indicating that zirconia is located predominantly outside the mesoporous channels as small zirconia nanoparticles for the lower loading, and predominantly inside the mesoporous channels for the higher loading. The concentration of medium–strong Lewis and Brønsted acid sites were determined by pyridine chemisorption monitored by IR spectroscopy. While the concentration of Brønsted acid sites (formed after sulfation) is linearly dependent on the amount of zirconia in SBA-15, a marked deviation is observed for Lewis acid sites. The same conclusion was derived from analysis of the dependence of the catalytic activity in Lewis- or Brønsted-acid-site-promoted reactions. The analysis of these results indicated that the characteristics of the zirconia nanoparticles deposited outside or inside the mesoporous silica channels differ in terms of acid features and in turn of catalytic reactivity.