Functionalized SBA-15 Materials Research Articles

Advancing Adsorption and Separation with Modified SBA-15: A Comprehensive Review and Future Perspectives.

Mesoporous silica SBA-15 has emerged as a promising adsorbent and separation material due to its unique structural and physicochemical properties. To further enhance its performance, various surface modification strategies, including metal oxide and noble metal incorporation for improved catalytic activity and stability, organic functionalization with amino and thiol groups for enhanced adsorption capacity and selectivity, and inorganic-organic composite modification for synergistic effects, have been extensively explored. This review provides a comprehensive overview of the recent advances in the surface modification of SBA-15 for adsorption and separation applications. The synthesis methods, structural properties, and advantages of SBA-15 are discussed, followed by a detailed analysis of the different modification strategies and their structure-performance relationships. The adsorption and separation performance of functionalized SBA-15 materials in the removal of organic pollutants, heavy metal ions, gases, and biomolecules, as well as in chromatographic and solid-liquid separation, is critically evaluated. Despite the significant progress, challenges and opportunities for future research are identified, including the development of low-cost and sustainable synthesis routes, rational design of SBA-15-based materials with tailored properties, and integration into practical applications. This review aims to guide future research efforts in developing advanced SBA-15-based materials for sustainable environmental and industrial applications, with an emphasis on green and scalable modification strategies.

SBA-15 mesoporous particles with adsorbed cresol red dye and functionalized with 3-aminopropyl groups: Materials properties and dye release studies

Research in the field of sensing has focused on tailoring the responsiveness of materials through the variation in materials properties achieved via functionalization of the mesoporous matrix. pH indicator dyes capable of protonation/deprotonation reactions are known to display different forms, resulting in changes in colour. This research focused on the preparation of mesoporous substrates SBA-15 with integrated pH indicator dye o-cresolsulphonephtalein (cresol red) grafted with (3-aminopropy)trimethoxysilane (gaining functionalized-SBA-15 material) in order to gain a colour change response following release of the dye. UV-Vis reflectance and absorbance spectra were used to evaluate forms of cresol red. The textural properties, including specific surface area, pore size distribution and pore volume were evaluated using nitrogen sorption, and XRD analysis was conducted to evaluate crystallinity of the material and pore ordering. The presence of 3-aminopropyl groups was determined by thermal decomposition using TGA–DSC/MS. The functionalized SBA-15 materials loaded with cresol red mostly retained ordering of the pores and showed a slight reduction in surface area. Functionalization changed the surface properties of the material. In the non-functionalized SBA-15, cresol red was present in both double (H2L) and single (HL−) protonated forms, whereas in the functionalized SBA-15 the deprotonated L2−form prevailed. Through desorption experiments cresol red was successfully desorbed from selected sample to different media. The change of colour caused by alterations in the form of the dye once released from the mesoporous silica material into the medium was confirmed. The form of cresol red released was determined by the pH of the medium.

Adsorption behavior of cationic dye on mesoporous silica SBA-15 carried by calcium alginate beads: Experimental and molecular dynamics study

This paper describes the fabrication of composites beads based on functionalized SBA-15 materials encapsulated in calcium alginate (ALG) which are employed for removing methylene blue (MB). The prepared composites beads were characterized by various techniques such as XRD, FTIR, SEM, zeta potential measurements and TGA. As results, the SBA-15 material was well immobilized in the alginate matrix. The best adsorbent beads were determined by evaluating the kinetics of MB adsorption from aqueous solutions. It has also been established that the hydrogel beads with a pure SBA-15 have a negative surface and therefore a greater capacity for adsorption of cationic dye compared to the adsorbents beads containing amine-functionalized SBA-15. The combination of two matrices (Pure SBA-15 and alginate) containing negatively charged surfaces generates excellent properties through the removal of the MB dye. The maximum adsorption capacity of the ALG-SBA-15 composite was 333.33 mg.g−1. The adsorption well followed the pseudo-second-order kinetics and Langmuir isotherm, and was spontaneous endothermic process. The adsorption of MB dye on the ALG-SBA-15 beads could be easily realized through electrostatic interactions and hydrogen bonding. Furthermore, molecular dynamic (MD) simulations were performed on pure SBA-15 structure models with different pore diameters to get a glimpse on the dynamic behavior of MB molecules upon adsorption on the mesoporous material.

Solvent-Free Environmentally Benign Approach for the Selective Olefin Epoxidation Catalyzed by Mn(III)-Immobilized Mesoporous Nanoarchitectonics.

Immobilization of transition metal complexes at the surface of 2D-hexagonal functionalized SBA-15 material is one of the promising strategies in designing an efficient catalytic system for the olefin epoxidation reaction. Here we have immobilized Mn(III) on the Schiff-base anchore 2D-hexagonally ordered functionalised mesoporous SBA-15 material. Powder X-ray diffraction (PXRD), N₂-sorption and high resolution transmission electron microscopic (HRTEM) studies of the resulting SBA-15-SB-Mn material suggested 2D-hexagonally ordered porous nanostructure and X-ray photoelectron spectroscopy (XPS) analysis suggested the presence of surface bound Mn(III) species in this nanomaterial. This mesoporous material showed excellent performance in the selective catalytic oxidation of various alkenes to the corresponding epoxides in the presence of tert-butyl hydroperoxide (TBHP, 70% aqueous solution) as oxidant under solvent-free mild reaction conditions together with high recycling efficiency.

RETRACTED: Photoactive CeO2/SBA-15 functionalized materials as efficient systems for mono-dehydration of sugar alcohols

Abstract Photocatalytic mono-dehydration of D-sorbitol and D-mannitol was conducted using photoactive cerium dioxide functionalized SBA-15 materials. Synthesized photocatalysts exhibited excellent activities for mono-dehydration products in water. The presence of cyanuric chloride and poly(vinyl alcohol) as additional ligand enhanced catalyst activity and durability.

Cytotoxicity study and influence of SBA-15 surface polarity and pH on adsorption and release properties of anticancer agent pemetrexed.

Mesoporous material SBA-15 was functionalized with different polar and nonpolar groups: 3-aminopropyl, (SBA-15-NH2), 3-isocyanatopropyl (SBA-15-NCO), 3-mercaptopropyl (SBA-15-SH), methyl (SBA-15-CH3) and phenyl (SBA-15-Ph). The resulting surface grafted materials were investigated as matrices for controlled drug delivery. Anticancer agent, pemetrexed (disodium pemetrexed heptahydrate) was selected as a model drug and loaded in the unmodified and functionalized SBA-15 materials. Materials were characterized by elemental analysis, infrared spectroscopy, transmission electron microscopy, nitrogen adsorption/desorption analysis, small angle X-ray scattering, powder X-ray diffraction, solid state NMR spectroscopy and thermogravimetry. It was shown that surface modification has an impact on both encapsulated drug amount and release properties. Release experiments were performed into two media with different pH: simulated body fluid (pH = 7.4) and simulated gastric fluid (pH = 2). In general, the effect of pH was reflected by the lower release of pemetrexed under acidic conditions (pH = 2) compared to slightly alkaline saline environment (pH = 7.4). The release rate of pemetrexed from propylamine-, propylisocyanate- and phenyl-modified SBA-15 was found to be effectively controlled by intermolecular interactions as compared to that from pure SBA-15, SBA-15-SH, and SBA-15-CH3, that evidenced a steady and similar release. The highest release was observed for methyl-functionalized material whose hydrophobic surface accelerates the pemetrexed release. The data obtained from release studies were fitted using various kinetic models to determine the pemetrexed release mechanism and its release rate. The best correlations were found for Korsmeyer-Peppas and Higuchi models. Moreover, the theoretical three-parameter model for drug release kinetic was applied to calculate the strength of drug-support interactions. The in vitro cell study was performed on SKBR3 cancer cells and obtained results demonstrated that the modification of the mesoporous silica material by grafted polar/nonpolar groups may significantly affect the compatibility of this material with cells, drug release from this material and subsequent biological activity of PEM.

Efficient Production of Medium-Chain Structured Phospholipids over Mesoporous Organosulfonic Acid-Functionalized SBA-15 Catalysts

It is highly desirable that efficient recoverable heterogeneous catalysts should be developed to replace the costly biocatalysts used in producing structured phospholipids (SPLs) with medium-chain fatty acids (MCFAs). Thus, mesoporous propyl and phenyl sulfonic acid-functionalized SBA-15 materials synthesized via surface modification methods were investigated for the soybean lecithin interesterification with methyl caprate or caprylate. The physicochemical properties of the synthesized solid acids were deeply studied by small-angle X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared and pyridine adsorption, etc. to build the possible structure–performance relationships. The results revealed that amounts of organosulfonic acid groups were successfully grafted onto the SBA-15 support, and most of the surface acid sites contained in the as-prepared organic–inorganic hybrid samples were assigned as strong Brӧnsted acid sites. Notably, the functionalized SBA-15 materials exhibited promising catalytic behaviors in producing MCFA-enriched SPLs under mild conditions (40 °C, 6 h) when compared with commercial Amberlyst-15 and typical phospholipases or lipases, mostly due to their high surface area, ordered structure and adequate Brӧnsted acid sites. Besides, the as-prepared materials could be easily recycled five times without obvious deactivation. This work might shed light on alternative catalysts for SPL production instead of the costly enzymes.

Chiral Cr(III)-salen complex embedded over sulfonic acid functionalized mesoporous SBA-15 material as an efficient catalyst for the asymmetric Henry reaction

Designing novel catalytic system for efficient synthesis of enantiomerically pure β-hydroxy nitroalkanes is a challenging area of research. Herein, we have designed a chiral heterogeneous catalyst through the successful loading of chiral Cr(III)-salen complex over sulfonic acid functionalized SBA-15 material. The catalyst has been thoroughly characterized by powder XRD, N2 adsorption/desorption, XPS, HR-TEM, CHN, AAS analyses and FT-IR spectroscopy. The reactivity of the catalyst has been examined in the enantioselective Henry reaction, where different substituted aromatic, heteroaromatic as well as aliphatic aldehydes produced corresponding β-hydroxy nitroalkanes with excellent product yields (up to 90%) and enantioselectivities (up to 91%). Moreover, this protocol has also been employed as the key-step to prepare enantiomerically pure drug (R)-(-)-isoproterenol from 3,4-dimethoxybenzaldehyde.

Ag nanoparticle-decorated, ordered mesoporous silica as an efficient electrocatalyst for alkaline water oxidation reaction.

In recent years, several novel strategies for speeding up the slow kinetics of the water oxidation reaction have attracted considerable attention for generation of O2. This is particularly important from the environmental perspective. Here we report a SBA-15 type, 2D-hexagonal functionalized mesoporous organosilica material as support for small Ag nanoparticles (NPs) by grafting the silica surface with 3-aminopropyltriethoxysilane, followed by chemical impregnation of Ag NPs at its surface, to obtain a AgNPs@SBA-NH2 material. The AgNPs@SBA-NH2 has been thoroughly characterized using several instrumental tools, such as powder X-ray diffraction, ultra-high resolution transition electron microscopy, N2 sorption, FT-IR spectroscopy, thermogravimetric and differential thermal analysis and X-ray photoelectron spectroscopy. High Brunauer-Emmett-Teller (BET) surface area and fine dispersion of Ag NPs throughout the surface of the amine-functionalized mesoporous material could enhance the rate of oxygen evolution reaction (OER) activity for AgNPs@SBA-NH2 in the electrochemical water splitting reaction.

Interaction between adsorbed molecules and tailor made large chelating ligands grafted on SBA-15 studied by means of thermoporometry

Modified mesoporous silicas were examined as adsorbents for efficient removal of model pollutants from wastewaters. Functionalized SBA-15 materials for capture of cationic pollutants such as metal cations and anionic dyes were obtained using post-synthesis grafting method. Large organic ligands containing acetyloacetone, 2-aminopyridine, 2-aminothiazole and 2-aminobenzothiazole groups were incorporated into the adsorbents' structure. The adsorption capacities reached levels of 38.6, 43.1, 64.3, 68.6 and 88.9 mg g−1 for Cu2+, Rose Bengal, Congo Red, Levafix Amber CA gran and Methyl Orange, respectively. Moreover, the adsorption efficiency depended on a type of the model molecule and a type of the surface chelating group. The pores' size and the pores' volume of the hybrid materials before and after adsorption was determined in hydrated state using thermoporometry. For the first time, by means of this methodology, it was possible to propose a model of interactions between the adsorbed molecules and the grafted organosilanes. Adsorption of organic dyes resulted in most cases in formation of J-aggregates.

Adsorption of Th(IV) and U(VI) on functionalized SBA-15 mesoporous silica materials using fixed bed column method; breakthrough curves prediction and modeling

ABSTRACTRemoval–separation of Th(IV)/U(VI) by Schiff base functionalized SBA-15 materials SBA/SA and SBA/EnSA using fixed bed column method was investigated. The effects of flow rate and bed height were studied and the experimental breakthrough curves were obtained. The analysis of experimental data showed that the breakthrough time and exhaustion time, metal uptake capacity and total metal removal increased with reducing the flow rate, and with increasing the bed height. Thomas and Yan models were applied to the experimental data for evaluating the dynamic behavior and the characteristic parameters of the column for the process design.

Intraparticle Diffusional versus Site Effects on Reaction Pathways in Liquid-Phase Cross Aldol Reactions.

Chemo- and regioselectivity in a heterogeneously catalyzed cross aldol reaction were directed by tuning the nature of the sites, textural properties, and reaction conditions. Catalysts included sulfonic acid-functionalized resins or SBA-15 with varying particle size or pore diameter, H-BEA zeolites, and Sn-BEA zeotype; conditions were 25 °C to 170 °C in organic media. Benzaldehyde and 2-butanone yielded branched (reaction at -CH2 - of butanone) and linear (reaction at -CH3 ) addition and condensation products; and fission of the branched aldol led to β-methyl styrene and acetic acid. Strong acids promoted the dehydration step, and regioselectivity originated from preferred formation of the branched aldol. Both, resins and functionalized SBA-15 materials yielded predominantly the branched condensation product, unless particle morphology or temperature moved the reaction into the diffusion-limited regime, in which case more fission products were formed, corresponding to Wheeler Type II selectivity. For H-form zeolites, fission of the branched aldol competed with dehydration of the linear aldol, possibly because weaker acidity or steric restrictions prevented dehydration of the branched aldol.

Functionalized SBA-15 material with grafted [sbnd]CO2H group as an efficient heterogeneous acid catalyst for the fixation of CO2 on epoxides under atmospheric pressure

Carboxylic acid functionalized SBA-15 material AFS-1 has been synthesized through post synthetic route and the mesophase of the material has been characterized by powder X-ray diffraction, transmission electron microscopy and N2 adsorption/desorption studies. Post-synthesis functionalization resulted high loading of carboxylic acid groups at the surface of highly ordered mesoporous silica. The material showed excellent catalytic activity for the production of cyclic carbonates from a wide range of epoxides in the presence of carbon dioxide (CO2) at atmospheric pressure and room temperature. The catalyst can be reused five times without significant loss of its catalytic activity.

Covalent grafting of cobalt carbonyl cluster on functionalized mesoporous SBA- 15 molecular sieve and its applications towards hydroformylation of 1-octene

Cobalt carbonyl cluster was anchored through a facile route on the surface of organo-functionalized SBA-15 molecular sieve by post-synthetic approach. The successful grafting of organofunctional ligand and cobalt carbonyl cluster was evident thorough 29Si-MAS NMR, 13C-MAS NMR and FT-IR studies. The resultant cobalt clusters anchored functionalized SBA-15 material (SBA-15-RCo) showed promising catalytic activity on hydroformylation of 1-octene (97% conversion) with excellent selective towards hydroformylated products (90%).

Production of Structured Lipids Containing Medium-Chain Fatty Acids by Soybean Oil Acidolysis Using SBA-15-pr-NH2–HPW Catalyst in a Heterogeneous Manner

The Keggin-type H3PW12O40 (HPW) was successfully anchored onto the surface of amino-functionalized SBA-15 silica by means of protonating of amino-functionalized silica with the phosphotungstic acid. The as-prepared heterogeneous catalysts were fully characterized at the current research by using small-angle XRD, FT-IR, TEM, SEM, solid-state NMR, and nitrogen porosimetry measurement. The characterization results showed that the functionalized SBA-15 materials still retained the ordered mesoporous structure of SBA-15 silica with high surface area, and meanwhile the primary Keggin structure of heteropolyanions could be also remained intact upon the immobilization of the HPW. By using this solid catalyst, the acidolysis of soybean oil with caprylic or capric acid was carried out in a batch reactor to produce structured lipids containing medium-chain fatty acids. The influence of reaction parameters, such as the substrate ratio, reaction temperature, catalyst loading, and reaction time, on the acidolysis react...

Influence of structural, textural and surface properties of mesostructured silica and aluminosilicate carriers on aminoglycoside uptake and in vitro delivery

This work assessed the influence of structural, textural and surface features of mesostructured silica and aluminosilicate carriers on aminoglycosides encapsulation and in vitro release. A series of pure and functionalized mesostructured silica, as well as aluminosilicates, which belong to MCM-41, MCM-48 and SBA-15 classes, and two aminoglycosides with related structure, amikacin and kanamycin as biologically-active molecules were employed in order to prepare drug delivery systems. No significant toxicity of studied mesoporous carriers on MEF cells after 72h of continuous exposure to 100μg/mL nanoparticles was noticed. The mesostructured supports and amikacin- and kanamycin-based hybrid samples were characterized by small- and wide-angle XRD, FT-IR spectroscopy, thermogravimetric analysis, and N2 sorption isotherms. The uptake values for all amikacin-based hybrids are higher than those for kanamycin counterparts. Moreover, the first antibiotic can be loaded on functionalized (with 3-aminopropyl or methyl groups) SBA-15-type materials, unlike the last drug. Amikacin loaded into the mesopores of AlSBA-15 and SBA-15 vehicles exhibited a slower delivery rate than from MCM-48 and functionalized SBA-15 materials. Different than amikacin-based hybrids, kanamycin loaded on aluminosilicates (AlMCM-41 and AlSBA-15) caused faster delivery, the highest value of drug cumulative release at 24h being obtained for AlMCM-41 support.

New insights in the deactivation of sulfonic modified SBA-15 catalysts for biodiesel production from low-grade oleaginous feedstock

Arenesulfonic-acid functionalized SBA-15 materials have been used in the production of biodiesel from low grade oleaginous feedstock. These materials display an outstanding catalytic activity, being able to promote the transformation of crude palm oil with methanol into fatty acid methyl esters with high yield (85%) under mild reaction conditions. However, high sensitivity of the catalyst against poisoning by different substances has also been detected. Thus, alkaline metal cations, such as sodium or potassium exert a negative influence on the catalytic activity of these materials, being necessary amounts around 500ppm of sodium in the reaction media to decrease the catalytic activity of these materials to a half of its initial value in just two reaction runs. The deactivation of arenesulfonic acid functionalized SBA-15 materials seems to occur in this case by ion exchange of the acid protons at the sulfonic groups. Organic unsaponifiable compounds like lecithin or retinol also induce a negative influence in the catalytic activity of these sulfonic acid-based materials, though not so intense as in the case of alkaline metals. The deactivating mechanism associated to the influence of the organic compounds seems to be linked to the adsorption of such substances onto the catalytic acid sites as well as on the silica surface. The accumulation of lecithin in the surface of catalyst, observed by means of thermogravimetric analysis, suggest the creation of a strong interaction, probably by ion pair, between this compound and the sulfonic acid group.

Microscale scavenging of pentachlorophenol in water using amine and tripolyphosphate-grafted SBA-15 silica: Batch and modeling studies

Mesoporous silica SBA-15 meets most criteria for selection of water treatment adsorbents such as high specific surface area, large pore-size, chemical inertness, repertory of surface functional groups, good thermal stability, selectivity, regenerability, and low cost of manufacture. However, its use for water treatment is still largely unexplored. SBA-15 and its functionalized derivatives of aminopropyltriethoxysilane (SA) and tripolyphosphate (ST) were synthesized, characterized, and used to investigate pentachlorophenol (PCP) removal from aqueous solutions. Functionalization improved SBA-15 capacity for PCP removal from solution in accordance with the trend SBA-15 < ST < SA. Sorption rate experiments data fit the Lagergren pseudo-second order kinetics model. Intra-particle diffusion indicated that the sorption is controlled by two mechanisms: intra-particle and equilibrium diffusion. Adsorptive pore-filling and electrostatic interactions were implicated in the removal of PCP from solution. Electrostatic interaction led to ≥75% increase in sorption upon functionalization. The equilibrium sorption data of the PCP on these mesoporous materials fits the Freundlich isotherm. Desorption hysteresis was low for the pristine SBA-15, but the functionalized SBA-15 materials showed higher hysteresis. The results imply that functionalized SBA-15 sorbents are promising materials for microscale scavenging of PCP in solution.

Investigation of ammonium ion removal from aqueous solutions using arene- and propylsulfonic Acid functionalized mesoporous silica adsorbents.

To counter environmental threats to the water resources polluted by NH, which is common in wastewaters and agricultural runoff, adsorption using mesoporous functional materials represents a promising alternative to existing treatment methods. In this study, adsorption of NH ions from aqueous solutions was investigated on arene- and propylsulfonic acid functionalized SBA-15 mesoporous silica materials. The adsorbents were synthesized via co-condensation and post-synthesis grafting procedures. Adsorbents were characterized by means of X-ray diffraction, N physisorption, titration, and elemental analyses. The effects of pH, NH initial concentration, temperature, adsorbent loading, organosilane molar ratio, and presence of competitive species on the performance of the adsorbent materials were examined. All the adsorbents having an organosilane/silica molar ratio of 1:5 displayed maximum adsorption capacity around approximately 25 mg g NH at the lowest temperature investigated, 5°C. This capacity decreased with increasing temperature. For a given initial NH concentration, the removal efficiency () increased with increasing adsorbent loading. For instance, increased from 24 to 59% when the adsorbent loading was increased from 2 to 10 g L at 25°C. The adsorption isotherms were well described by a Langmuir model equation. Adsorption capacity improved with increasing organosilane/silica molar ratio, reaching 42 mg g NH with a ratio of 2:5 at 25°C. Arene- and propylsulfonic acid functionalized SBA-15 materials synthesized via co-condensation and post-synthesis grafting proved to be effective high-capacity adsorbents for the removal of NH ions from aqueous solutions.

Preparation of Low Calorie Structured Lipids Catalyzed by 1,5,7-Triazabicyclo[4.4.0]dec-5-ene(TBD)-functionalized Mesoporous SBA-15 Silica in a Heterogeneous Manner

1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD, a strong bicyclic guanidine base) functionalized SBA-15 material has been found to be an efficient solid catalyst for the interesterification between tributyrin and methyl stearate in a solvent-free system for the production of low-calorie structured lipid (LCSL). The solid base catalyst was characterized by using small-angle X-ray scattering, Fourier transform infrared spectra, thermo gravimetric analysis, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption, and elemental analysis techniques. The obtained LCSL was analyzed by reverse-phase high-performance liquid chromatography for triacylglycerol composition. The influence of various reaction parameters, such as the substrate ratio, reaction temperature, and reaction time, on the interesterification reaction was investigated systematically. More than 90% LCSL was obtained at 80 °C within 1 h when the methyl stearate/tributyrin molar ratio of 2:1 was employed. The obtained solid catalyst could be recovered easily and reused for several recycles with a negligible loss of activity. By using the solid base catalyst, an eco-friendly more benign process for the interesterification reaction in a heterogeneous manner was developed.