Microporous and Mesoporous Materials最新文献

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.

The present study investigates the structural stability and adsorption behavior of ultrahigh CO₂-loaded pure-silica zeolites chabazite (CHA) and ITQ-12 (ITW) under high pressure conditions. To analyze these properties, we have utilized in situ synchrotron-based X-ray powder diffraction techniques. Lattice indexation provides information of the filling process and, through Rietveld refinements and Fourier recycling methods, we have been able to (i) determine the location and amount of guest carbon dioxide molecules within the cavities of pure-SiO₂ CHA zeolite and (ii) tentatively determine that within the channels of the porous pure-SiO₂ ITW framework. The filling of the zeolite pores with CO₂ molecules was found to have a positive impact on the structural stability of both CHA and ITW under compression, which do not undergo pressure-induced amorphization up to 12.2 GPa and 15.9 GPa, respectively. Interestingly, low compressibility takes place in CHA zeolite below 4 GPa during CO₂ loading and a second-order phase transition occurs in CO₂-filled ITW zeolite at 2.1 GPa. These results highlight the influence of CO₂ adsorption on the compressibility behavior of these zeolites. Overall, our study provides detailed insights into the structural behavior of CO₂-loaded CHA and ITW under high pressure and allows comparison with other pure silica zeolites described in the literature.

UVM-7 is a bimodal mesoporous silica material that can be prepared in a short time with microwave assisted synthesis (MAS). It is prepared following the atrane route, that allows the synthesis of mixed silicas including other elements with homogeneous distribution. We report herein the preparation of Ti-UVM-7 with using the atrane route in combination with MAS with solid-state generators. The synthesis has been optimized and scaled-up in batch. Also, the flow synthesis has been developed. These materials have not been prepared before using solid-state generators, nor microwave-assisted flow chemistry. The materials have been characterized by XRD, N₂ adsorption-desorption, TEM, EDX, Raman, and Z potential. The materials can be prepared in less than 10 min with a Si/Ti ratio of up to 3.8, and a homogeneous Ti distribution within the UVM-7 silica structure. Scaled-up synthesis produces 33 g of Ti-UVM-7 in 10 min and 12 g h⁻¹ in batch and flow synthesis respectively. The optical properties and sun protection factor of the resulting materials were studied. The band gap decreases as titanium concentration increases, reaching 4.1 eV for the highest concentration. Life Cycle Assessment confirms a strong reduction in the impact derived from the scale-up with similar values of approximately 10 points in the single score for the preparation of 1 kg of Ti-UVM-7.