Microporous and Mesoporous Materials最新文献

For chlorinated volatile organic compounds (CVOCs), it is critical to design and fabricate applicable noble metal catalysts to exhibit superior catalytic performance in catalytic oxidation under both dry air and 5.0 vol% H₂O conditions. In pursuit of this goal, a facile strategy was developed to prepare a series of Pt-supported catalysts for the elimination of o-dichlorobenzene (o-DCB). Among these catalysts, Pt/CeAlZrO_x possessed excellent activity (T₉₀ = 285 °C) and Pt/LaAlO_x showed outstanding selectivity within/without 5.0 vol% H₂O, attributed to the strong interaction of multi-components, abundance of adsorbed oxygen, prominent redox properties, and suitable acidity. According to the analysis results of density functional theory (DFT), the introduction of Pt can significantly improve the adsorption and activation of o-DCB molecules on the catalysts. Specifically, the action of Marse-van Krevelen (MvK) combining with Langmuir-Hinshelwood (L-H) mechanism was proposed. In general, this work provides promising candidates and valuable insights into the comprehensive improvement of o-DCB catalytic degradation for industrial application.

Pervaporation (PV) is considered a promising energy-efficient process for recovering ethanol from fermentation liquids. In this study, ethanol separation characteristics were elucidated using mixed-matrix pervaporation membranes composed of hydrophobic polymers (PDMS) and high-silica ZSM-5 (HSZ). The selectivity and flux of ethanol/water were both improved when HSZ content in PDMS matrices was increased — at 50 wt% HSZ content the selectivity reached 15 and the flux of ethanol was improved to 0.05 kg/m²/hr. A new method was demonstrated to quantify the local thickness of the PDMS matrices by cross-sectional SEM binarization and inscribed circle analysis. PDMS matrices became more uniform with an increase in the HSZ content. The uniform presence of the PDMS matrices can be interpreted as more uniform dispersion of HSZ particles. An increase in total length of PDMS-HSZ interface resulted in improved ethanol permeability. NMR analysis showed that the molecular mobility of PDMS was restricted. Those results suggest an increase in the physical interaction between PDMS and HSZ. This study demonstrated a new analytical method for understanding the local thickness of the PDMS matrices and the interfacial state of mixed-matrix pervaporation membranes.

L-type zeolite with Co²⁺ and Cu²⁺ ions in 3d-transition-metal ions were prepared via ion exchange. The suspension containing these zeolite was used for slip-casting under a 12 T magnetic field applied perpendicular to the substrate surface, resulting in an orientation parallel to the c-axis for Co-L and an orientation vertical to the c-axis for Cu-L. The orientation behavior was strongly affected by the magnetocrystalline anisotropy of the L-type zeolite introduced by Co²⁺ and Cu²⁺ ions. X-ray absorption fine structure and diffuse-reflectance measurements indicated that the introduced Co²⁺ and Cu²⁺ ions formed six-coordinated hydration complexes in the zeolite structure. These hydrated complexes have a distorted octahedral structure. The results suggest that the stable direction of the magnetic moment of the hydration complex at site B of L-type zeolite depends on the strain direction. The Co²⁺ and Cu²⁺ hydration complexes have different strain directions, and the difference in orientation is speculated to be due to the different stable directions of the magnetic moment within the zeolite.

Mesoporous carbon nanospheres have attracted significant attention in the microwave absorption (MA) field due to the broad benefits provided by their mesoporous structure. This study presents a facile hard template strategy to construct distinctive 3D N/O co-doped mesoporous carbon nanospheres (NOCS). The high surface area, abundant mesopores, and high nitrogen (N) doping levels, with proper defects on the surface provide multiple sites to absorb electromagnetic waves (EMW). Mesoporous carbon nanospheres achieve significant reflection loss (RL) of −48.19 dB and extensive effective absorption bandwidth (EAB) up to 5.52 GHz. Moreover, computer simulation technology (CST) demonstrated that all simulated Radar cross-section (RCS) values were below 20 dB m². Thus, this work holds significant promise for effective microwave absorbers using mesoporous carbon nanospheres.

Mechanical stability is a crucial property for the industrial implementation of heterogeneous catalysts and adsorbents. Both particle size and shape need to be investigated for each application where, typically, a compromise between mass transfer and pressure drop needs to be understood. In this study, we investigate the mechanical stability of a fragile mesostructured cellular foam material, formed of 3D aluminosilicate struts and porous cages, that are connected through windows. Successful pelletization was found at ca. 20 MPa, where the structural and textural properties are either unaltered or minimally modified. This condition is satisfactory for the final application of the pelletized material, though a lower-limit pressure could still be optimized. The use of higher pelletization pressures was observed to increase disorder in the systems. The structure contracts, the cage's size decreases markedly leading to more disordered wormhole-like pores. The decrease in cage/pore size seems to compensate for the structural densification, resulting in relatively constant BET areas. The pore volume's decrease is in agreement with the smaller cage sizes and densification. The damage and the mechanism causing this damage differ from that observed in conventional mesoporous materials. Besides the successful pelletization conditions and identification of damage mechanism, it is also noteworthy to highlight that values for BET area can be misleading when assessing mechanical stability; at high pressures, the BET areas remain fairly constant despite significant changes in pore size and structure are observed.

In this work, the KIT-6 silica support functionalized with different contents of sulfonic groups (10 and 15 % S/Si) was employed to prepare mesoporous acid catalysts. Catalysts with modified properties were obtained introducing the functional groups by co-condensation or grafting methods.

The catalytic activity was studied in the glicerolysis of soybean derived fatty acids, for the obtention of mono-, di- and triglycerides using a batch reactor. Vacuum was applied to eliminate water from the system and shift the equilibrium to the products. The effect of the catalytic formulation was studied modifying the synthesis method and the sulfonic content. Additionally, a comprehensive study was conducted regarding the distribution of products and by-products. The effect of reaction temperature, molar ratio of reactants (free fatty acids: glycerol) and catalyst concentration on conversion and selectivity was analyzed.

The solids were studied by numerous characterization techniques. It was found that the KIT-6 catalysts functionalized with sulfonic groups synthesized by grafting retained the original structure of KIT-6, as opposed to those modified by co-condensation. However, all the catalysts provided adequate catalytic activities in glycerolysis with relatively high conversions of 90 % in 3 h of reaction, indicating that these materials have potential for a more environmentally friendly process. In addition to the reversible esterification, secondary reactions occurred that decrease the selectivity to the desired products, which could be attributed to the presence of insaturations in the carbonaceous chain of the fatty acids used. Additionally, the recyclability of the catalysts was evaluated; demonstrating sustained catalytic activity for up to three cycles.

We developed a three-step synthesis strategy to obtain Sn-incorporated MFI-type zeolite nanosponge (Sn-MFI-ns) assembled by ultrathin (∼2.5 nm) zeolite frameworks possessing uniform-sized (∼4 nm) mesopores: 1) synthesis of MFI-type borosilicate nanosponge using a zeolite structure-directing-surfactant, 2) deboronation of the borosilicate using HNO₃, and 3) gas-phase incorporation of Sn into the boron-vacant sites via silanol groups using (CH₃)₂SnCl₂ as a precursor. The Sn-MFI-ns shows high crystallinity, consequently high thermal stability, and highly porous structure. The Sn content can be systematically controlled by the amount of the precursor, with Si/Sn ratios ranging from 30 to 200. The Sn species is highly dispersed over entire range of the zeolite surfaces, acting as Lewis acid sites. Due to the highly mesoporous structure, the Sn-MFI-ns has a significant number of Lewis acid sites on the external surfaces and mesopore walls, which are easily accessible to bulky molecules, compared to solely microporous zeolite (Sn-bulk-MFI). Consequently, the Sn-MFI-ns exhibits much higher catalytic activity than the Sn-bulk-MFI with high product selectivity in Baeyer-Villiger oxidation of 2-adamantanone, a molecule larger than the micropore apertures of MFI-type zeolite. The activity of Sn-MFI-ns is comparable to Sn-MCM-41 exposing almost all Sn to mesopore walls, advantageous to the bulky molecules’ reaction.

The successful one-pot synthesis of MCM-41/MFI composite is mainly concentrated on the trivalent heteroatom of Al³⁺ and Fe³⁺, however there are almost no reports about the one-pot synthesis of Ti-MCM-41/MFI composite. In this work, we reported the one-pot synthesis of Ti-MCM-41/MFI composite with a temperature-gradient hydrothermal strategy using hexadecyl trimethylammonium bromide CTAB and silicalite-1 seed as structure directing agents as well as ammonia solution as alkali source, and its application as heterogeneous catalyst in the cyclohexene epoxidation reactions. The impact of Si/Ti molar ratio and ammonia dosage as well as CTAB amount on the formation and property of Ti-MCM-41/MFI composite were systematically investigated. In addition, a possible partial transformation mechanism of Ti-MCM-41/MFI composite sample was proposed. The synthesized Ti-HMZ-50-N3.77-Se0.05 sample with ordered mesoporous structure and high content of framework titanium active centers revealed the eminent cyclohexene epoxidation performance, achieving a 32.51 % of cyclohexene conversion and a 61.27 % selectivity of cyclohexene oxide within 5 h of reaction.

Secondary caries develops between the dental filling and the tooth surface because the filling materials lack antibacterial properties. In our study, we successfully created Ag-mesoporous bioactive glass (MBG) with antibacterial properties using a one-pot synthesis method and modified its surface with bisphenol A-glycidyl methacrylate (Bis-GMA). We tested the antibacterial and remineralizing abilities of the resin matrix. The 10 wt% Bis-GMA-Ag-MBG composite resin showed excellent remineralizing and antibacterial abilities, and the presence of Ag nanoparticles did not affect these properties during the photocuring process. Cell viability experiments confirmed that the 10 wt% Bis-GMA-Ag-MBG composite resin is biocompatible. This study emphasizes the potential of Bis-GMA-Ag-MBG (10 wt%) as a new dental composite resin with bioactive, remineralizing, and antibacterial properties, addressing the critical need for durable and preventive dental materials against secondary caries.

To be used at scale, adsorbents must be shaped into macroscopic objects, e.g. pellets, granules, and monoliths. Shaping may involve various processing steps and additives that collectively contribute to the final equilibrium and kinetic sorption properties of the adsorbent. Understanding the fundamental links between these processing steps and the resulting sorption performance is needed to rationalise the design of shaped adsorbents. Our study aims to advance the state of knowledge in this area. By focusing on ZIF-8, a prototypical metal organic framework (MOF), and CO₂, a common small gas adsorbate, we compared a commercial binderless ZIF-8 extrudate and two purpose-made ZIF-8 pellets shaped with a blend of binders. We used analytical, spectroscopic, and imaging techniques to characterise the samples’ chemical, textural, and morphological properties. In addition, we collected equilibrium and kinetic CO₂ adsorption data at 283, 293, and 303 K and up to 1 bar. The binderless ZIF-8 extrudate exhibited a homogeneous structure with BET area, micro- and meso-porosity only slightly reduced compared to ZIF-8 powder. The ZIF-8 pellets also maintained the overall BET area of the ZIF-8 powder, but displayed enhanced macroporosity and skeletal density as well as reduced microporosity – features that likely result from the pressure-induced strains of pelletisation. The extrudates are much less mechanically robust than the pellets. All samples displayed CO₂ adsorption capacity in line with the CO₂ uptake of their respective components. The CO₂ kinetics measurements reveal clear distinctions between binderless ZIF-8 extrudate and ZIF-8 pellets, the latter indicating a behaviour associated with the additional presence of macropores. Our study presents quantifiable evidence for the effect of adsorbent shaping on gas adsorption equilibria and kinetics, providing a valuable resource for preliminary process design.