Microporous and Mesoporous Materials最新文献

Sn–Al-Beta zeolites with less silanol defects were synthesized in fluoride media. The effects of the amount of organic template (tetraethylammonium hydroxide, TEAOH), mineralizer (NH₄F), Al and Sn on the synthesis, acidity and catalytic performance were systematically studied. The synthesized Sn–Al-Beta zeolites were characterized by XRD, SEM, ²⁷Al MAS NMR, UV–vis DRS and FT-IR spectroscopy of hydroxy region and pyridine adsorption. The optimum values of n_TEAOH/n_Si and n_F-/n_Si were same (0.3) for synthesizing Sn–Al-Beta with high crystallinity at 140 °C for 7 d. Moreover, decreasing n_F-/n_Si facilitated the incorporation of Al into the framework. The crystallization rate of Sn–Al-Beta is similar with that of Sn-Beta. Sn was promoted to enter the framework with the increase of Al content, while elevating Sn content has no effect on the incorporation of Al into the framework. The catalytic performance of Sn–Al-Beta was investigated for conversion of glucose to 5-hydroxymethylfurfural in water-containing solvent. Sn–Al-Beta synthesized in fluoride media is more stable than the post-synthesized sample.

The 24-membered ring -SYT type extra-large pore zeolite, denoted as DESO-SYSU-3, has been synthesized by employing N,N′-diethylsophoridine and trimethylsulfanium in a mixed-template system, where the N,N′-diethylsophoridine and trimethylsulfanium played different roles in the crystallization process. A single usage of N,N′-diethylsophoridine led to the formation of an unknown phase (donated as SYSU-5). These results reveal that the utilization of alkaloid-derived organic structure-directing agents (OSDAs) is an efficient synthetic strategy to produce specific extra-large pore zeolites and related structures. Compared to the prototype SYSU-3, the addition of TMSF into the system not only improved the silicon content in the framework of DESO-SYSU-3 but also facilitated the generation of carbon dots (CDs) confined in extra-large pore structure. The structure and the proposed formation mechanism of CDs were investigated based on HRTEM, XPS, FI-IR, UV–Vis, Raman and photoluminescence spectrum. The CDs@zeolite composite exhibited intriguing optical properties of both fluorescence and room temperature phosphorescence, respectively. This work extends extra-large pore zeolite as the matrix for the development of CDs@zeolite composites with tunable optical properties.

To solve the easy deactivation of zeolite catalyst in methanol to propylene (MTP) reaction, hierarchical ZSM-11 zeolite composed of loosely aggregating ultra-small nanocrystals (∼10 nm) were prepared using vinyltrimethoxysilane-methyl methacrylate (VTMS-MMA) copolymer latex as a “bond blocker”. The structure and texture properties of the as-synthesized zeolite were systematically characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ adsorption desorption, NH₃-TPD, and thermogravimetric analysis (TG). The results showed that as compared with the parent ZSM-11-0 without adding the latex, the hierarchically porous ZSM-11-x (1 ≤ x ≤ 3) zeolite synthesized with VTMS-MMA copolymer latex had a higher surface area, mesopore volume, and moderate acidity. Due to the nanocrystallization of the primary grain in the polycrystalline aggregates, the micropores channels in the as-synthesized ZSM-11-x (1 ≤ x ≤ 3) were effectively shortened and abundant intercrystalline mesopores resulted from loosely aggregating of the ultrasmall primary crystals were therefore introduced, which offered the optimized ZSM-11-1 catalysts with a longer catalyst life (46 h) and a higher propylene yield (∼40.5 %) in MTP.

Nitrofurazone (NFZ), a nitroimidazole antibiotic, can cause serious toxicity when overused, its quantification is crucial for human health. Herein, crab shell waste is converted into porous biochar at a high temperature, which can be employed for the establishment of an electrochemical sensor for the quantitative detection of NFZ. The morphological and structural properties of the crab shell carbon at different temperatures were characterized by SEM, XRD, FT-IR and N₂ adsorption-desorption analyses. The crab shell carbon prepared at 500 °C (C-CS-500) and 700 °C (C-CS-700) is calcite-based and contains micro-fibrillar similar to chitin structure, while the crab shell carbon prepared at 900 °C (C-CS-900) is lime-based and lacks the similar structure. And the synergistic influence of calcite-based composition and micro-fibrillar structure of crab shell carbon offered strong electron-transport properties and a large electrode active at a higher carbonized temperature. The electrochemical signals demonstrated that the crab shell carbon prepared at 700 °C provided enhanced sensing capability for rapid NFZ detection with a wide linear range of 0.40–80 μM, a high sensitivity of 0.55 μA μM⁻¹ and a low detection limit of 0.11 μM (S/N = 3), as compared to the crab shell carbon prepared at 500 °C and 900 °C. In addition, the sensor can also be utilized to quantify nitrofurazone in the real drug (compound cod liver oil ointment) with satisfactory recovery.

We present a study on incorporating spiropyran photoactive molecules into the UiO-66-NH₂ scaffold. Initially, we modified spiropyran molecules by introducing functional groups to facilitate covalent bonding with the MOF structure. Spiropyran molecules with carboxylic groups demonstrated the ability to coordinate zirconium in defect pores of the MOF. Alternatively, the aldehyde group showed potential for forming C–N bonds with amino groups of BDC-NH₂ linkers. To validate the formation of C–N bonds within the MOF scaffold, we synthesized a complex salt of spiropyran and individual BDC-NH₂ linkers. DFT calculations support our conclusions. We observed that upon introducing the photoactive moiety, the UiO-66-NH₂ framework exhibited photoresponse, as demonstrated by FTIR experiments. Based on experimental data and computational results, we hypothesize that both incorporation mechanisms are viable in the functionalization process. However, steric hindrances may impede the incorporation of spiropyran into the pores, leading to surface modification instead. The elucidated mechanisms hold promise for the development of photoresponsive MOF-based smart materials.

Carbon monoxide adsorption on alkali-metal exchanged chabazites (M-CHA, where M = Li, Na, K) was investigated across various Si/Al ratios. The study reveals significant insights into the adsorption behavior, including the persistence of cationic preferences with decreasing Si/Al ratios and the existence of multiple-center interactions involving alkali-metal cations and CO. Results show that for high-silica M-CHA zeolites, CO adsorption is effectively described by single and dual adsorption site models, with cation preferences varying by type. In low-silica zeolites, cation positions are primarily influenced by the aluminum distribution and Coulombic interactions. However, the propensity for single-site cation positions (Si/Al→∞) is preserved to a certain degree. The most noticeable example is the small difference between SIII’ occupancies (cations in 8-membered ring windows) in Na-CHA-2 and K-CHA-2 (0.80 vs. 0.85) that strongly influences the rate of diffusion of CO in the M-CHA-2 samples. While FT-IR spectra of high-silica zeolites can be accurately described using cation site stabilities, interaction energies, and CO stretching frequencies, predicting spectra of low-silica chabazites requires a statistical approach and/or molecular dynamics simulations at the DFT level. The findings demonstrate that the dynamical behavior of adsorbates changes dramatically between different alkali metal-exchanged chabazites, highlighting the complex nature of CO adsorption at multiple Lewis acid sites.

Crystallizing zeolites with isotropic properties is critical to the chemical industry but can be extremely challenging as small deviations in the synthesis conditions can have extreme effects on the final products. Easily implemented in-situ monitoring systems could make a real difference, but very few experimental methodologies cater to the specific needs of applications relying on harsh, hyper-alkaline conditions involving multiphasic systems such as Hydrated Silicate Ionic Liquids. Differential impedance spectroscopy (DIS) promises to enable such studies. It remains highly accurate despite possible electrode degradation or scaling. This study showcases how in-situ differential impedance measurements not only enable reliable detection of crystallization of even minimal amounts of zeolite product but also illustrates how the unique combination of in situ DIS and in situ, ²⁷Al NMR provides insight into complex, incongruent zeolite crystallization processes.

Several variants of ETS-4 were synthesized through single-cation and binary-cation exchange, with a particular emphasis on Sr/Ba-ETS-4. The impact of binary-cation exchange on the structural characteristics was investigated using various analytical techniques, including XRD, FESEM, EDX, ICP-MS, TGA, and FT-IR analysis. The effect of mixed Sr and Ba exchange within ETS-4 on the adsorption, separation, and kinetic behavior of nitrogen and methane gases was explored utilizing the volumetric method at 30 °C and up to 100 kPa. Additionally, the investigation extended to examining the influence on diffusion coefficients employing the macropore-micropore kinetic model. ICP-MS results revealed a competitive advantage of barium in the exchange process among incoming cations. Notably, significant discrepancies in the adsorption capacity for nitrogen and methane gases were observed between the Sr-ETS-4 and Ba-ETS-4 samples. Experimental isotherm data suggested that the Sips model offered the most suitable fit, unlike the Langmuir or Freundlich models. Among the Sr/Ba-ETS-4 adsorbents investigated, the adsorbent with the highest barium content in the framework exhibited superior nitrogen adsorption capacity (0.33 mmol/g) and the lowest methane adsorption capacity (0.07 mmol/g), leading to high nitrogen over methane equilibrium selectivity (3.12) and kinetic selectivity (167.6).

The conversion of CO₂ into methanol has emerged as a promising strategy for addressing climate change and optimizing the utilization of carbon resources. Conventional synthesis methods for Cu-based catalysts, such as co-precipitation, necessitate the consumption of substantial amounts of solvent and meticulous control over preparation conditions, while also being susceptible to deactivation by water during hydrogenation. Therefore, it is crucial to develop a catalyst that can be readily synthesized and exhibits outstanding performance and durability. In this study, we present an ultrafast (only 20 min), solid-phase grinding approach to fabricate CuO-ZnO@Cu-MOR catalysts for CO₂ hydrogenation to methanol. The resulting catalysts were comprehensively characterized using XRD, XPS, H₂-TPR, NH₃-TPD, SEM, HRTEM, and In-situ-FTIR techniques. Notably, the CuO-ZnO@Cu-MOR catalysts with a distinctive capsule-like structure displayed a high catalytic performance for CO₂ hydrogenation. The byproducts of methane and water produced by the CO₂ hydrogenation process were able to be further converted to methanol through Cu-MOR, leading to a significant enhancement of the methanol selectivity (95.6 %) and CO₂ conversion (22.8 %). Moreover, a long-term test lasting 300 h demonstrated constant catalytic performances and superior durability.

Despite of several decades lasting extensive research of bioactive and bioresorbable glasses the systematic parametrization and determination of the key factors affecting porosity and thermomechanical characteristics still remains challenging. Here, we present silica-phosphate glasses, with the composition 70SiO₂–20P₂O₅–(10-x)CaO–xTiO₂ (mol%; x = 0, 2.5, 5, and 7.5), prepared by sol-gel method and reinforced by titanium dioxide via titanium isopropoxide (TTIP) incorporation which demonstrated tunable variation of porosity from micro-to macro-region and superb mechanical integrity during the calcination process. The presence of 7.5 mol% TiO₂ promotes dimensional stability up to 1000 °C as investigated by thermomechanical analysis. The XRD showed the dominant presence of silicon phosphate [Si(P₂O₇)], titanium phosphate [Ti(P₂O₇)] and calcium phosphates [β-Ca(P₂O₆) and γ- Ca₂(P₂O₇)]. The effect of TiO₂ doping on the multiscale morphology and porosity was investigated by means of SEM, MIP, μCT, N₂ adsorption and USAXS/SAXS. Increasing TiO₂ content leads to the formation of open porosity up to 70 vol% and drives the formation of a refined interconnected macroporosity of 2–30 μm. In contrast, mesoporosity with a dominance of 3–6 nm pores decreases in all samples with increasing TiO₂ content. USAXS/SAXS revealed an increase in primary particle size with increasing TiO₂ content which is in good agreement with the nitrogen physisorption analysis showing that microporosity decreases with increasing TiO2 content.