Microporous and Mesoporous Materials最新文献

Boron-doped ordered mesoporous carbons (B-OMCs) were synthesized using different solvent types and compositions to study the effect of the solvent medium on the physical properties and oxygen reduction activities of the resultant structures. Materials were synthesized by a one-pot self-assembly method, using resorcinol and formaldehyde as carbon source, boric acid as boron source and triblock copolymer Pluronic F127 as the structure directing agent. Different solvents, namely ethanol, n-propanol, isopropanol and acetone were used as solvent media along with water as the cosolvent. Among different solvents, ethanol and n-propanol gave better-ordered structures and also had higher surface areas. At this stage, the highest boron doping percentage was obtained as 1.38 % with n-propanol. In the second stage, B-OMCs were synthesized with n-propanol in different water/n-propanol (W/N) molar ratios varying between 2.5 and 4.75. The orderliness was observed to be better in samples with low W/N ratios of 2.5 and 3.25 and the morphologies shifted from 2D to 3D interconnected type with the increase of water content. The average pore sizes of samples varied between 7.9 and 9.7 nm. On the other hand, the highest surface area (729 m²/g) and the highest boron doping percentage (1.53 %) were obtained with the W/N ratio of 4. XPS analysis showed that 23 % (w/w) of doped boron in this sample was in substitutional state while the remaining boron was found in mixed B–C and B–O states. Cyclic voltammetry measurements for the samples with W/N ratios of 2.5, 3.25 and 4 showed significant oxygen reduction activities at −0.28 and −0.29 V. Results showed that the properties of solvent play an effective role in the orderliness, pore structure and surface composition of B-OMCs, which in turn affect their electrochemical properties. Among different types of solvents, n-propanol can be used as an alternative to ethanol with the W/N ratio of 4 giving the highest surface area and boron doping percentage.

This scientific article investigates the adsorption of Ketoprofen using a novel zeolite template carbon (ZTC) characterized by X-ray diffraction (XRD) as a type 2 zeolite with a high surface area confirming its ZTC nature. The material exhibits excellent thermal stability, and scanning electron microscopy (SEM) reveals a well-defined and homogeneous structure. Kinetic studies indicate that the pseudo-first-order (PFO) model best describes adsorption, demonstrating rapid adsorption with high removal efficiency. Isotherm results reveal a theoretical maximum adsorption capacity of 280 mg g⁻¹ at 298 K, which is spontaneous, favorable, and exothermic. The ZTC can be efficiently utilized for up to 5 adsorption cycles, demonstrating its stability. Moreover, practical application in treating real effluents from a river water source showed a removal efficiency exceeding 84 % for the contaminants. The findings suggest the promising potential of ZTC in environmental remediation processes and advanced wastewater treatment.

Conventionally, mesoporous silica nanoparticles are prepared by catalysing silicon alkoxides using acids or bases and are highly important in storage, delivery, and catalysis. Here, for the first time, we demonstrate that a transition metal ion (such as Ni(II), Co(II), and Mn(II)) also catalyses the hydrolysis and condensation reactions of silicon alkoxides in aqueous media without any additional acid or base to synthesize mesostructured and micro/mesostructured silica nanoparticles. An aqueous solution of a transition metal salt (specifically, nitrate salts of Ni(II), Co(II), or Mn(II), or chloride and sulphate salts of Ni(II)), 10-Lauryl ether (C₁₂H₂₅(OCH₂CH₂)₁₀OH, C₁₂E₁₀) and cetyltrimethylammonium bromide (C₁₆H₃₃N(CH₃)₃Br, CTAB), and tetramethyl orthosilicate (TMOS) undergoes a precipitation reaction at room temperature, yielding ultra-small ordered mesostructured silica nanoparticles. These nanoparticles are subsequently calcined to produce mesoporous silica (meso-SiO₂) with a high surface area (680–871 m²/g), large pore-volume (2.2–3.71 cm³/g), and small pore-size (1.2–3.0 nm). Moreover, the counter anions of the salts play an important role in the assembly process to obtain nanoparticles with an additional well-defined secondary pore (7.5–33.4 nm or larger). Coordinated water of the metal ion and methoxy group of the silica source react to produce a complex in which two hydroxy sides are in close vicinity to speed up the condensation reaction. We propose a hydrolysis and condensation reaction mechanism for TMOS to highlight the role of the metal ion as a catalyst.

Silica material, particularly, fibrous nano-silica (FNS) is one of the potential scaffolds for hydrogen storage, however, low hydrogen adsorption limits its application. To improve its adsorption capacities, the incorporation of active metal, particularly magnesium (Mg), was prepared. FNS with well-developed pore structures and a good surface area were synthesized. Various amounts of Mg (1–5 wt%) were infiltrated into the FNS. To study the effect of metal loading, the adsorbents were characterized by their chemical structure, crystal phase, morphology/elemental composition, and textural properties. Subsequently, hydrogen adsorption studies were conducted where different reaction conditions, including metal loading, catalyst loading, and temperature were studied. Furthermore, kinetic and thermodynamic studies were conducted based on the Langmuir and Van't Hoff models. The results of the characterizations show that the Mg metal was well dispersed into the porous FNS with no significant changes in the original structure. The optimum adsorption of 1.90 wt% was achieved at 1.0 wt% Mg loading, 0.1 g catalyst loading, and 423 K temperature. Kinetic studies demonstrated that the adsorption process fits the pseudo-second-order reaction. The 1%Mg/FNS adsorbents showed good reusability where 5 runs were conducted with <5 % loss in activity. Therefore, this result indicated that infiltration of Mg into the silica is one of the most active approaches in improving the hydrogen adsorption capacities of FNS.

The conversion of renewable compounds to versatile platform molecules over environmentally friendly heterogeneous catalysts is a major challenge. Zeolites stand as active, selective, and reusable solid catalysts for various acid-catalyzed reactions involved in the one-pot cascade transformation of polysaccharides to 5-hydroxymethylfurfural (HMF), a platform molecule opening the way to various valuable chemicals. However, the acidity-performance relationships of zeolite catalysts in HMF synthesis have not been fully elucidated. Here, we have addressed the effect of acid site nature in zeolite catalysts for sucrose-to-HMF transformation by comparing the performance of conventional Al-substituted IWW zeolite with that of Sn-, Zr-, and Ge-containing zeolite catalysts of the same structure. Ge-associated acid sites were found to exhibit superior HMF selectivity compared to Sn, Zr, and Al acid centers, while experiencing evolution into Brønsted acid centers during the catalytic run. The conversion of sucrose over germanosilicate zeolites enhances with increasing catalyst pore diameter or decreasing crystal size. Specifically, the extra-large pore Ge-UTL catalyst, featuring intersecting 14- and 12-ring pores (crystal size 10 × 20 × <1 μm), and large-pore Ge-IWW with 12-, 10- and 8-ring pores (crystal sizes of 1 μm) showed a yield of targeted HMF comparable to or even exceeding the values previously reported for homogeneous or heterogeneous catalysis (54 % after 3 h at 120 °C). Ge-IWW catalyst demonstrated reusability across a minimum of 3 catalytic runs, while in situ structural transformation precluded stable performance of Ge-UTL catalyst in the repetitive catalytic cycles. The results of this study highlight zeolites with uncharacteristic chemical compositions as active, selective, and reusable catalysts for highly demanding applications in biomass valorization.

The synthesis of zeolite ETS-10 is strongly influenced by factors such as pH, the amount of the structure-directing agent, hydrothermal temperature and duration, which collectively affect the material’s morphology and structure. This study thoroughly investigates the effects of these parameters on the synthesis of ETS-10 zeolite using TiCl₃ and a waterglass solution. Characterization of the materials was performed through X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), and nitrogen isotherm adsorption-desorption at 77 K (BET-BJH) techniques. The findings indicate that pH and the structure-directing agent significantly influenced the phase composition, while hydrothermal temperature predominantly determined the crystallization rate of ETS-10. Optimal synthesis conditions were established at an initial pH of 11, employing 0.3 g of the structure-directing agent and conducting hydrothermal crystallization at 230 °C for 24 h. Under these conditions, the ETS-10 zeolite produced exhibited a high surface area of 300.1 m²/g, making it effective in removing Pb²⁺ ions from solution. In particular, when tested under optimal conditions (pH 5) for 600 min, Pb (II) adsorption by ETS-10 reached a maximum uptake capacity of 956.19 mg/g, as determined by the Langmuir isotherm model. This capacity surpasses that of as-synthesized ETS-10 prepared from alternative Ti sources and other materials used in previous studies on Pb(II) adsorption.

1-Octene, a linear α-olefin, can be used as a comonomer for producing plastics, oils, waxes, and surfactants. High-purity 1-octene can be obtained by removing paraffin byproducts using energy-intensive distillation. Adsorptive separation using porous material–based adsorbents is a promising alternative to distillation. Most reported adsorbents are zeolites, which preferentially adsorb 1-octene rather than n-octane owing to their polar framework. However, the existing studies are insufficient for investigating apolar adsorbents that adsorb more amounts of n-octane than 1-octene. Herein, the adsorption properties of the apolar adsorbents, zeolitic imidazolate frameworks-8 (ZIF-8) and ZIF-67, obtained from a n-octane/1-octene liquid binary mixture were systematically investigated by conducting batch adsorption experiments for the n-octane volume fraction of 10 %–90 %. Results show that ZIF-8 and ZIF-67 are promising adsorbents for the selective adsorption of n-octane owing to the preferential adsorption of n-octane in the micropores of the ZIFs at the high concentration of n-octane. Configurational-bias grand canonical Monte Carlo simulations confirm that the host–adsorbate energy between ZIF-8 and n-octane is higher than that between ZIF-8 and 1-octene, whereas the host–adsorbate energy between ZIF-67 and n-octane is similar to that between ZIF-67 and 1-octene.

MIL-126(Fe) shows great potential for aqueous phase drug adsorption due to its permanent porosity and easy modification. Herein, we utilized the ligand installation method to introduce two ligands, 2-amino terephthalic acid (NH₂-BDC) and 2-nitro terephthalic acid (NO₂-BDC), into MIL-126(Fe) to prepare MIL-126(Fe)-NH₂ and MIL-126(Fe)-NO₂, respectively. Various analytical tools were used to confirm the successful installation of the 1, 4-phthalic acid (BDC) series of ligands, as well as the successful introduction of amino (-NH₂) and nitro (-NO₂) groups. The presence of both -NH₂ and -NO₂ groups improved the adsorption of TC by the adsorbent material, with -NH₂ groups having a stronger influence on the enhancement. The experimental results indicated that MIL-126(Fe)-NH₂ had the highest adsorption performance at the optimal pH of 7, achieving a static adsorption capacity of 326.5 mg/g, which was about twice the adsorption capacity of the original MIL-126(Fe). X-ray photoelectron spectroscopy (XPS) determined that the adsorption of TC by MIL-126(Fe)-NH₂ relies mainly on π-π interaction and Fe-N coordination bonds. Furthermore, the higher adsorption capacity of MIL-126(Fe)-NH₂ can be attributed to the O-H⋯N hydrogen bonds interaction between -NH₂ and the phenolic hydroxyl group (Ph-OH) in the TC molecule.

Alkyl levulinate is a kind of high value chemicals derived from biomass. Here, a nanosponge ZSM-5 supporting zirconium phosphate (ZrPO/NPZ) catalyst is prepared and used for catalytic transfer hydrogenation of furfural (FUR) to produce isopropyl levulinate (IPL) using isopropanol as H-donor. ZrPO specie provides Lewis acid sites together with additional Brønsted acid sites by ZSM-5 zeolite. Using the hierarchical ZSM-5 with exposed surface area as support, the dispersion of ZrPO active species increases, which facilitates the adsorption and conversion of FUR with the generation of 2-(isopropoxymethyl)furan (IPMF). The moderate Brønsted acid sites by zeolite promote the adsorption and activation of isopropanol, thus increasing the conversion rates of intermediate IPMF with formation of IPL. Furthermore, improved proportions of Brønsted/Lewis was detected with the increase of P/Zr ratios in the prepared catalysts, which is adverse for conversion of FUR. The optimized ZrPO/NPZ catalyst with P/Zr of 1 gives the best catalytic performance with IPL yield of ∼69 wt% after 3 h reaction at 200 °C (TOF of 6.98 mmol g⁻¹ h⁻¹), which provides an essential catalyst to produce IPL from FUR.

Methane dehydroaromatization (MDA) is a promising approach for direct methane transformation to aromatics and hydrogen. The benchmark catalyst Mo/H-ZSM-5 struggles to find commercial adoption because of thermodynamically-limited yields and rapid coking on Brønsted acid and molybdenum carbide species, especially on zeolite external surfaces. Here, gas-phase atomic layer deposition (ALD) overcoats H-ZSM-5 external surfaces with SiO₂ or Al₂O₃. NH₃-TPD, HRTEM, and textural properties show that these overcoats exclusively passivate zeolite external surfaces. Under MDA conditions, SiO₂ gives softer coke and increases cumulative benzene yields by 25 %, while Al₂O₃ strongly decreases yields. H₂-TPR and UV–visible and Raman spectroscopy show how the overcoats redisperse the MoO_x precatalysts, especially over multiple deactivation and isothermal oxidative regeneration cycles. Combined with ²⁷Al-MAS NMR, MoO_x redistribution and dealumination are seen as the causes of long-term deactivation over multiple regeneration cycles, and this process continues to occur regardless of the overcoat. Overall, the deposition of a small amount of silica on the outer surface of Mo/H-ZSM-5 reduces the formation of hard coke, which could be regenerated by milder methods such as hydrogen treatment.