Microporous and Mesoporous Materials最新文献

In this study, a novel silicon hydroxyl groups decorated long carbon chain grafted carbon fiber was synthesized, and a facile fabrication method was developed to produce reactive carbon fiber-silica aerogel composite with chemical crosslinking structure. Scanning electron microscopy images showed that silica aerogel matrix is wrapped on the surface of reactive carbon fibers. The reactive carbon fibers facilitated obstacle in shrinkage, and aerogel composites exhibited microporous behavior with average diameter of about 1.8 nm. Fourier-transform infrared and X-ray photoelectron spectroscopy confirmed the strong interfacial interaction between reactive carbon fibers and silica matrix. The modification mechanism of silicon hydroxyl groups decorated long carbon chain grafted carbon fiber, and the chemical crosslinking in aerogel composite were proposed. The reactive carbon fiber-silica aerogel composites synthesized in this work had been proved to have low density, excellent mechanical property, good tailoring performance, improved thermal stability, low thermal conductivity, high flame retardancy, high thermal insulation property, and superhydrophilicity. Hence, this work provided a theoretical basis for improving the performance and expanding the application of silica aerogel.

The facile synthesis of composite material, combining magnetic CoO with ZIF-67 (CoO@ZIF-67), has been successfully developed. This innovative approach involves the growth of a crystalline (ZIF-67) derived from stable and abundant CoO, resulting in the formation of the composite magnetic CoO@ZIF-67. The synthesis method, based on a solid-state thermal approach (SST), is straightforward and efficient, conducted in a single step and under solvent-free conditions, leading to the homogeneously composite formation of CoO@ZIF-67. Importantly, the composite magnetic CoO@ZIF-67 material has demonstrated remarkable catalytic performance as a heterogeneous catalyst in various reactions while requiring a lower catalyst loading under comparable conditions to those needed for pure ZIF-67. A significant advantage of this newly developed composite catalyst, CoO@ZIF-67, is its ease of separation and recyclability. The recovery catalyst can be achieved through the use of an external magnet, making it a standout feature of the green and environmentally friendly synthetic procedure used in its production.

Naphtha cracking is the most common process for producing light olefins such as ethylene, propylene, and butene. This process consumes enormous amounts of energy, so decreasing the energy consumption and operating temperature is an urgent issue. To decrease the reaction temperature for naphtha cracking, we focused on the metal-assisted cracking reaction, in which paraffin is first dehydrogenated into the corresponding olefin on a metal catalyst, and the produced olefin is then decomposed into light olefins. To effectively realize metal-assisted cracking, we considered metal-encapsulated zeolite catalysts to be useful. In metal-encapsulated zeolite catalysts, the dehydrogenation reaction proceeds inside the zeolite particles, and the dehydrogenated intermediates can access the solid-acid sites frequently. In this study, Rh nanoparticle encapsulated ZSM-5 catalysts (Rh@ZSM-5) were employed for the metal-assisted cracking of n-hexane. Rh@ZSM-5 exhibited significantly high activity for n-hexane cracking below 450 °C owing to the metal encapsulation structure and close proximity between the metal and solid-acid sites. Furthermore, the effects of reaction conditions, reaction temperature, amounts of metal and solid-acid sites, and contact time on metal-assisted n-hexane cracking over the Rh@ZSM-5 catalysts were investigated. The highest light-olefin yield of 38.6 carbon mol% was achieved by the conversion of n-hexane over Rh@ZSM-5 using 0.3 wt% Rh loading, an Si/Al ratio of 100, temperature of 450 °C, reaction time of 0.5 h, and W/F of 2 h.

Thymol is synthesized from m-cresol alkylation reaction with 2-propanol. A few commercial zeolites have been tested in this reaction, but the influence of acidity and porosity of a zeolite on the m-cresol conversion and thymol yield is scarcely studied. Isomorphously-substituted Al-, Ga-, Fe-, B-, and In-UTL with different heteroelements and thus different ratio between strong and weak sites give insight into the effect of acidity. Isoreticular zeolites Al-UTL, Al-IPC-7, and Al-IPC-2 with different pore sizes reveal the effect of porosity. In this study, m-cresol conversion was far from comparable over Al-UTL or Ga-UTL (X = 18–19 %) and Fe-UTL, B-UTL, or In-UTL (X = 2–3 %) having different concentration of strong Brønsted acid sites. Thymol yield was also higher over Al- and Ga-UTL (Y = 11–13 %) than over Fe-, B-, and In-UTL (Y = 1–2 %). The easier accessibility to the strong Brønsted acid sites in Al-UTL, provided by bigger pore sizes, resulted in higher m-cresol conversion and thymol yield compared to Al-IPC-7 (X = 15 % and Y = 8 %) and Al-IPC-2 (X = 6 % and Y = 2 %). In addition, the stronger Brønsted acidity and large and extra-large porosity in Al-UTL and Ga-UTL facilitated the rearrangement of isopropyl-3-methylphenyl ether - the product of the O-alkylation pathway - to thymol. Thus, Al-UTL and Ga-UTL (along with Al-FAU reference material) confirmed the optimum structural properties for a high selectivity to thymol.

This work reports using the solvent-free method for the first time in the literature using the surfactant Vorasurf504 (V504) to produce mesoporous carbons (MC). In addition to V504, resorcinol was used as a carbon source, and terephthalaldehyde as a cross-linking agent. Three materials were produced with different proportions of resorcinol: V504, 1:1 (R1V), 1:2 (R2V), and 1:3 (R3V). V504 enabled the production of large mesoporous carbon, mainly for the materials with higher proportions of surfactant. The average pore diameters of the materials varied between 5 and 29 nm, and the mesopore volumes were on the order of 0.922 cm³ g⁻¹. The three produced materials were applied to remove emerging contaminants (EC) with different structural dimensions: paracetamol (PA), atrazine (AT), tenofovir (TF), and ceftriaxone (CF). During the contact test, R2V and R3V showed removals above 90 % for all EC. However, due to its limited mesoporosity, the R1V material had its removal capacity reduced for contaminants of larger structural dimensions. Through kinetic and isotherm studies for systems involving paracetamol and ceftriaxone, it was proven that, in fact, not only the specific surface area but also the pore size and pore volume influence adsorption. As a result of this study, large mesoporous carbon could be produced using a surfactant that has not previously been investigated for the solvent-free method. Furthermore, the materials produced can be used as effective adsorbents for emerging contaminants of various structural dimensions.

DAPI (4′,6-diamidino-2-phenylindole, di-hydrochloride) is a photoactive dye used as a fluorescent marker for nucleic acids, due to its high affinity for the major groove in the DNA double helix. By following a Mayan-inspired recipe (namely grinding, heating and washing in H₂O), the DAPI molecule was fastened to the microporous framework of palygorskite – a clay mineral used to produce the famed Maya Blue pigment, whose fibrous crystals are carved by surface grooves similar in size to those of DNA – in order to obtain a newly designed fluorescent material. This hybrid composite was investigated with a multi-analytical approach, which includes FE-SEM-EDS, BET-specific surface area (SSA)/micropore volume measurements, thermogravimetry, UV–vis, fluorescence and FT-IR spectroscopies. Supramolecular interactions form between the clay and the dye already after grinding, apparently involving a two-step binding process. Evidence is found of an incipient, electrostatic interaction between cationic DAPI and the negatively charged surface of the palygorskite fibrils, which then evolves in H-bonding interaction between the dye amine groups and the zeolitic and/or structural water in the clay surface grooves. Heating and washing in H₂O seemingly deteriorate the composite morphology and stability, jeopardizing – rather than strengthening – the previously formed host/guest interactions. This hybrid composite, with remarkable stability and appreciable quantum yield, is potentially fit to be used as a low-cost, fluorescent material for applications such as spectrum manipulation technologies, sensors, optical devices, imaging and design-targeted drug-delivery systems.

Porous carbon is commonly used in the effective removal of antibiotics from water. The geometry of nanopores plays a vital role in determining the adsorption properties of porous carbon. Aiming to reveal the adsorption mechanism and the dependence on the porous geometry, the mass transfer and adsorption performance of tetracycline (TC) in various shaped carbon nanopores was observed in this study by molecular dynamics (MD) simulation. The results show that the molecular diffusion of water and TC in nanopores is confined than that in bulk solution. The mass transfer in cylindrical through pores (THC) is more efficient than that in blind pores. The accumulated presence probability of TCs within the nanopore of THC is over twice as high as in the blind nanopores. THC exhibits the best adsorption rate and capacity in this study, and the adsorption ability of the blind nannopores follows the order BHC-Cy (cylindrical blind pore) > BHC-Co (conical blind pore) > BHC-Sp (spherical blind pore). Both the cylindrical and bottom surface in BHC-Cy are effective adsorption sites, while the adsorption is seldom found in the bottoms of BHC-Co and BHC-Sp. Surface diffusion of adsorbed TC molecules along the carbon surface was investigated. The sphere-shaped blind pore was found unfavorable for the adsorption of TC from water.

A simple, cost-effective, and environmentally friendly strategy was proposed for synthesis of three types of zeolitic imidazolate frameworks (Co, Co/Zn, and Zn based/containing) with cuboid particle morphology. The structure of (Co, Co/Zn, Zn)-ZIFs was studied by scanning electron microscopy, x-ray diffraction, and low-temperature nitrogen adsorption-desorption. To obtain information about the possibility of potential liquid-phase application of the cuboid (Co, Co/Zn, Zn)-ZIFs, hydrolytic stability testing was carried out at ambient conditions. According to the results of flame atomic absorption spectroscopy of supernatant solutions and x-ray diffraction analysis of solid samples, the negligibly small cleavage of Co–N and especially Zn–N bonds takes place during the first day of experiment with no discernible influence on the structure integrity of the studied ZIF mateials. Long-term water exposure of Co-containing ZIF materials results in transition of metal cations into the solution and noticeable transformation of crystalline structure. The effectiveness of the synthesized (Co, Co/Zn, Zn)-ZIFs in sorption of methyl orange from aqueous solutions was studied in dependence on duration of contact and equilibrium concentration of azo dye. Obtained results were analyzed by kinetic (Lagergren and Ho-McKay) and equilibrium (Langmuir, Freundlich, and Dubinin–Radushkevich) adsorption models. It was found that the kinetics of methyl orange sorption by synthesized ZIF sorbents is best described with the Ho-McKay model. The equilibrium sorption on Co-ZIF and Zn-ZIF with cuboid particle morphology proceeds in accordance with the Langmuir model, whereas interaction with heterometallic Co/Zn-ZIF agrees with the Freundlich one. The mean free adsorption energy for sorption of azo dye by ZIF materials increases in the order Zn-ZIF < Co/Zn-ZIF < Co-ZIF. The x-ray diffraction studies of (Co, Co/Zn, Zn)-ZIF materials after methyl orange sorption proved the complete transformation of mixed ZIF-L/ZIF-67 phase of cuboid Co-ZIF to rhombic dodecahedral ZIF-67.

A new bioactive material was proposed by encapsulating thymol molecules and Zn²⁺ cations within the post-modified intracrystalline voids of hierarchical zeolite X crystals. To enhance the accessibility of thymol molecules within zeolite X crystals, commercial zeolite samples underwent post-synthesis treatment involving consecutive aqueous KCl, NH₄Cl, and Na₂H₂EDTA solutions. The gas adsorption method utilized the encapsulation of both Zn²⁺ cation and thymol molecules into the resulting hierarchical zeolite X framework, which demonstrated improved antimicrobial activity. While sole thymol-encapsulated zeolite X exhibited no antimicrobial activity against S. aureus, Zn²⁺ encapsulated zeolite X (ZnX), thymol encapsulated post-treated zeolite X (HX-thy), and both Zn²⁺ and thymol encapsulated post-treated zeolite X (ZnHX-thy) displayed zone of inhibition values of 18.7 mm, 25.0 mm, and 37.5 mm, respectively. Adding Zn²⁺ and creating a hierarchical pore system in the zeolite X framework altered the release profiles. The Higuchi kinetic release model has the highest R² value to describe the process of thymol release from X-thy, whereas the Elovich release model has the best fitting profile of thymol release kinetics from ZnX-thy, HX-thy, and ZnHX-thy. Results indicate that thymol and Zn²⁺ containing hierarchical porous materials could be beneficial tools for obtaining enhanced antibacterial activity and stability with reduced degradation and volatility of thymol with extended protection against microbial attack due to the controlled release. These findings highlight an innovative approach to designing sustainable and green materials, utilizing modified porous networks that encapsulate natural antibacterial compounds with environmentally benign metal ions.

To increase the yield of light olefins during the catalytic pyrolysis of alkanes, a novel hierarchical Fe-incorporated ZSM-5 molecular sieve (FeM-Z5) was synthesized using an Fe-based metal-organic framework (Fe-MOF) as a mesoporogen and iron source through the dry gel conversion (DGC) method. In contrast to the conventional method of incorporating Fe species into ZSM-5 via impregnation, the DGC method incorporates Fe species into the framework of ZSM-5, decreasing the amount of Brønsted (B) acid sites and thereby inhibiting the side reactions of hydrogen transfer during the catalytic pyrolysis of alkanes. Compared with the FeN-Z5 catalyst prepared by the DGC method with Fe(NO₃)₃ as an iron source, FeM-Z5 had a larger amount of strong B acid sites and more mesopores with a size range of 10–40 nm originating from the decomposition of Fe-MOF; these aspects improved n-pentane pyrolysis and ethylene and propylene diffusion. As a result, the optimal FeM-Z5 catalyst exhibited the highest yield of ethylene and propylene (33.4 wt%) and the lowest deactivation rate (0.07 %/h) among the prepared catalysts during the catalytic pyrolysis of n-pentane.