Scalable Synthesis of Uniform Mesoporous Aluminosilicate Microspheres with Controllable Size and Morphology and High Hydrothermal Stability for Efficient Acid Catalysis

Preparation of Al-doped mesoporous silica spheres (Al-MSSs) for the improvement of mechanical properties and aging resistance of dental resin composites

OBJECTIVE

The purpose of this study was to synthesize Al-doped mesoporous silica spheres (Al-MSSs) and evaluate the effect of them as functional fillers on the mechanical properties and aging resistance of dental resin composites.

METHODS

Al-MSSs were prepared by a two-step method. The effect of Al-MSSs on the performance of the composites was evaluated using neat resin matrix, commercial composites 3M Z350XT and samples containing mesoporous silica spheres (MSSs) and nonporous silica spheres (NSSs) as control. The neat resin matrix consisted of resin monomer (Bisphenol A glycerolate dimethacrylate/triethylene glycol dimethacrylate, 49.5/49.5, wt%) and photoinitiator (camphor quinone/Ethyl-4-dimethylaminobenzoate, 0.2/0.8, wt%). The mechanical properties (flexural strength, flexural modulus, compressive strength and microhardness) of them were evaluated by a universal testing machine and microhardness tester. The mechanical stabilities of the prepared composites in wet environment were evaluated by immersing them in deionized water at 37 °C. In addition, we evaluated the effect of Al-MSSs on other properties of the dental resin composites such as polymerization shrinkage, degree of conversion, curing depth, contact angle, water sorption and solubility according to ISO 4049: 2019.

RESULTS

The synthesized Al-MSSs possessed good dispersibility with an average particle size of about 505 ± 16 nm. The mechanical properties of resin composites gradually increased with the increase of the loading amounts of inorganic fillers. The reinforcing effect of Al-MSSs was similar to that of MSSs and better than that of the NSSs groups at the same filler loading. After aging in deionized water at 37 °C for 30 days, the mechanical properties of all resin composites decreased. However, the decrease percentage of the composites filled with Al-MSSs was significantly lower than the other groups, indicating that the stability of the dental composites in wet environments was significantly improved by the Al-MSSs fillers. Furthermore, Al-MSSs had no obvious influence on the biocompatibility and other properties of dental resins.

SIGNIFICANCE

The prepared Al-MSSs could effectively improve the mechanical properties and aging resistance without sacrificing other physic-chemical properties of dental resin composites.

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.

Deep Cracking of Bulky Hydrocarbons into Light Products via Tandem Catalysis over Uniform Interconnected ZSM-5@AlSBA-15 Composites

Deep cracking of bulky hydrocarbons on zeolite-containing catalysts into light products with high activity, desired selectivity, and long-term stability is demanded but challenging. Herein, the efficient deep cracking of 1,3,5-triisopropylbenzene (TIPB) on intimate ZSM-5@AlSBA-15 composites via tandem catalysis is demonstrated. The rapid aerosol-confined assembly enables the synthesis of the composites composed of a continuous AlSBA-15 matrix decorated with isolated ZSM-5 nanoparticles. The two components at various ZSM-5/AlSBA-15 mass ratios are uniformly mixed with chemically bonded pore walls, interconnected pores, and eliminated external surfaces of nanosized ZSM-5. The typical composite with a ZSM-5/AlSBA-15 mass ratio of 0.25 shows superior performance in TIPB cracking with outstanding activity (≈100% conversion) and deep cracking selectivity (mass of propylene + benzene > 60%) maintained for a long time (> 6 h) under a high TIPB flux (2 mL h-1), far better (several to tens of times higher) than the single-component and physically mixed catalysts and superior to literature results. The high performance is attributed to the cooperative tandem catalytic process, that is, selective and timely pre-cracking of TIPB to isopropylbenzene (IPB) in AlSBA-15 and subsequently timely diffusion and deep cracking of IPB in nanosized ZSM-5.

Comparative study on Al-SBA-15 prepared by spray drying and traditional methods for bulky hydrocarbon cracking: Properties, performance and influencing factors

Mesoporous aluminosilicates Al-SBA-15 with large pore sizes and suitable acid properties are promising substitutes to zeolites for catalytic cracking of bulky hydrocarbons without molecular diffusion limitation. The conventional processes to synthesize Al-SBA-15 are time-consuming and often suffer from low "framework" Al contents. Herein, Al-SBA-15 microspheres are synthesized using the rapid and scalable microfluidic jet spray drying technique. They possess uniform particle sizes (45-60 μm), variable surface morphologies, high surface areas (264-340 m2/g), uniform mesopores (3.8-4.9 nm) and rich acid sites (126-812 μmol/g) and high acid strength. Their physicochemical properties are compared with the counterparts synthesized using traditional hydrothermal and evaporation-induced self-assembly methods. The spray drying technique results in a higher incorporation of aluminum (Al) atoms into the silica "framework" compared to the other two methods. The catalytic cracking efficiencies of 1,3,5-triisopropylbenzene (TIPB) on the Al-SBA-15 materials synthesized using the three different methods and nanosized ZSM-5 are compared. The optimal spray-dried Al-SBA-15 exhibits the best performance with 100 % TIPB conversion, excellent selectivity (about 75 %) towards the formation of deeply cracked products (benzene and propylene) and high stability. The catalytic performances of the spray-dried Al-SBA-15 with varying Si/Al ratios are also compared. The reasons for the different performances of the different materials are discussed, where the mesopores, high acid density and strength are observed to play the most critical role. This work might provide a basis for the synthesis of mesoporous rich metal-substituted silica materials for different catalytic applications.

Synthesis of Well-Ordered Mesoporous Aluminosilicates with High Aluminum Contents: The Challenge and the Promise

SBA-15 has recently emerged as a potential material for the catalytic conversion of large molecules. Usually, SBA-15 has a low content of aluminum due to the conventional acidic synthesis medium. Although a few approaches have been adopted to prepare Al-SBA-15 with a high alumina content, it is still challenging to prepare well-ordered Al-SBA-15 with a high alumina content. Here, we demonstrate a facile synthesis process in neutral mediums for the grafting of Al into the framework of SBA-15. This approach relies mainly on the dissociation of Si-O-Si bonds and the polymerization of Si-O-Si/Al bonds promoted by sodium persulfate (SPS) in neutral mediums. In this way, well-ordered Al-SBA-15 with a high aluminum content and enhanced acidity was obtained. Results of X-ray fluorescence spectroscopy (XRF) showed an n(SiO₂)/n(Al₂O₃) ratio of 13.7, much lower than that of the conventional sample (21.7) obtained in acidic medium. The characterization results indicated the presence of a well-ordered Al-containing mesophase with high hydrothermal stability. Notably, the Al content and the acidity of Al-SBA-15 can be tuned by changing the SPS amount.

Obtaining of Mesoporous Aluminosilicates with High Hydrothermal Stability by Composite Organic Templates: Utility and Mechanism

We have reported the synthesis of mesoporous aluminosilicates (MAs) with high hydrothermal stability via assembly of basic characteristic structure units of typical microporous zeolite Y. In spite of this, high consumption of organic template and H₂O remains a major obstacle to its industrial application. Herein, a facile and effective strategy called "composite templates" was employed to decrease significantly the amount of P123 and H₂O. In this method, composite micelles of P123/poly(vinyl alcohol) (PVA) could be more easily dispersed in the solution due to the lowering of water's surface tension caused by the free hydroxyl groups of PVA. Moreover, the improved assembly ability of composite micelles in high concentration solution leads to the synthesis of hydrothermally stable MAs with 45% decrease of organic template P123 and 81% that of water amount. It was found that by the introduction of composite templates, the textural properties such as the surface area of materials, volume of pore, size of pore, and thickness were enlarged simultaneously. Meanwhile, this article presented an understanding into the assembly of composite micelles in the process of synthesis of MAs.

Synthesis of Sulfonated Porous Organic Polymers with a Hydrophobic Core for Efficient Acidic Catalysis in Organic Transformations

Synthesis of sulfonated porous polymers with improved hydrophobicity and stability is of extreme importance in both academic research and industrial applications. However, there is often a trade-off between acidity and surface hydrophobicity of sulfonated polymers. In this study, we report a strategy for the synthesis of sulfonated porous organic polymers (S-PT) with improved hydrophobicity via free radical polymerization method by using a rigid and large multidentate monomer, 1,3,5-tri(4-vinylphenyl)-benzene, having a hydrophobic core. The results of vapor adsorption measurement show that S-PT has more hydrophobic properties than sulfonated poly(divinylbenzene) (S-PD), attributed to the hydrophobic core of its multidentate monomer. Furthermore, the optimization of sulfonation time established a balance between surface acidity and hydrophobicity. Under optimized conditions, S-PT afforded up to 113 mmol g^-1  h^-1 TOF in the esterification of oleic acid with methanol, more active than commercial Amberlyst-15 with TOF of 15 mmol g^-1  h^-1 and Nafion NR50 with TOF of 7 mmol g^-1  h^-1 . We believe that the findings of this study will provide useful insights to advance the design and synthesis of solid acid catalysts for organic transformations.

Growth kinetic control over MgFe2O4 to tune Fe occupancy and metal–support interactions for optimum catalytic performance

For the first time, the growth behavior with size-dependent Fe occupancies at different sites of MgFe₂O₄ was examined. Hybrid catalysts of Pt/MgFe₂O₄ with a support size of 20.6 nm exhibited an optimal performance of CO oxidation.