Microporous and Mesoporous Materials最新文献

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.

The existence of newly identified water contaminants, such as endocrine-disrupting substances (EDCs), in polluted water sources represents substantial environmental and health concerns. Over novel mixed-linker porous calcium-based metal-organic frameworks (Ca-MIX), the simultaneous adsorptive removal of 17-ethynylestradiol (EE2), perfluorooctanoic acid (PFOA), and bisphenol A (BPA) from aqueous solutions has been studied in terms of adsorption kinetics, adsorption isotherms, and water chemistry effects. The adsorption isotherm and kinetics fit the Langmuir model well and followed pseudo-second-order kinetics. Generally, all three compounds adsorb over Ca-MIX depending on the chemical properties of both the adsorbate–adsorbent and water matrix chemistry. Electrostatic and hydrophobic interactions may explain the adsorption mechanism between EDCs and Ca-MIX. The order from the best to worst removal efficiency was EE2 > PFOA > BPA when Ca-MIX was used as the adsorbent. In conclusion, it can be suggested that this material could be used as an adsorbent capable of removing harmful emerging contaminants in water at trace exposure levels.

In the refining industry, Y-type faujasite (FAU) plays an irreplaceable role, being widely used to convert crude oil into more valuable products such as gasoline. However, the demand for fuels and chemicals stimulates the search for alternatives, showing the applications of FAU beyond producing value-added chemicals from petroleum-based derivatives. These alternative applications are further enhanced from active sites that emerge in zeolites when iron is incorporated by a sonochemical treatment. Given that ultrasonic irradiation promotes mass transfer, uniform coverage of active sites is expected to produce more efficient catalysts. Likewise, Fe-zeolites catalyze a wide range of reactions in mild conditions, linked to the research of bio-refinery, biomimicry and environmental remediation. This work explores the potential of a Fe-Y zeolite prepared by a sono-assisted ion exchange method in different applications: biomass conversion (lactose hydrolysis), enzyme mimetic materials (partial oxidation of benzene to phenol) and transformation of renewable energy (photodegradation of nitrobenzene and rhodamine B). The modification of FAU was performed at different sonication times 5, 15, 30 and 120 min and characterized by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), N₂ adsorption-desorption isotherms, magnetic and non-magnetic thermogravimetric analysis (MTGA and TGA), zeta potential (ζ), Fourier-transformed Infrared (ATR-FTIR), and ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS). Finding that the modification of zeolite Y with Fe species enhances its activity for the tested applications, owing their catalytic activity primarily to α-Fe (II) sites. Presenting the sono-assisted ion exchange method as an alternative for introducing Fe species and enhancing the catalytic activity of zeolites.

Novel three-dimensional hierarchical flower-like calcium sulfate microspheres (CSMs) were successfully prepared with the assistance of polyethylene glycol, trisodium citrate, and polyacrylic acid. The CSMs were monodispersed as flower-like microspheres constructed from interspersed nanosheets. Their average diameter and Brunauer–Emmett–Teller specific surface area were 15 μm and 16.09 m²/g, respectively. The prepared CSMs were employed as adsorbents in cadmium (Cd(II)) removal from wastewater and their Cd(II) adsorption performances were analyzed. The adsorption kinetic data were best fitted to the pseudo-first-order kinetic model and the experimental isotherm data were precisely fitted to the Freundlich isothermal model. The maximum adsorption capacity of the CSMs could reach up to 18.13 mg/g at 293 K under neutral conditions, affirming the potential utility of the CSMs in Cd(II) removal from wastewater.

This study aims to explore the process of pure CHA zeolite production by a hydrothermal magadiite transformation method, with the chemical formulation of 36 NaOH: 40 SiO₂: Al₂O₃: 400H₂O, running for 7 h at 80 °C with 12 wt% seeds. Considering various synthesis factors such as NaOH/SiO₂, temperature, and seeds dosage etc., XRD, SEM, FT-IR, Solid-state MAS NMR and ESI-MS were applied to investigated to discuss the transformation behavior and mechanism in both solid and liquid phase. The results indicated that the changes of secondary building units had a formation sequence progresses from 6 R s to D6Rs, and oligomers in liquid phases would take part in the formation of CHA framework. In conclusion, the study demonstrates a novel pathway for the highly efficient and green synthesis of CHA zeolite via seed-assisted hydrothermal conversion of magadiite.

Converting lignin waste into carbon hybrid catalysts for water electrolysis engenders a beneficial scenario for both the valorization of waste carbon resources and the reduction of hydrogen production costs, which remains a grand challenge. Hence, we report a novel lignin-derived carbon hybrid electrocatalyst as a low-cost and highly efficient bifunctional electrocatalyst for overall water splitting, prepared by a feasible strategy involving NaCl-assisted pyrolysis and subsequent oxidation-phosphorization. Notably, this strategy can not only regulate the composition of CoP/CoO_x nano-heterostructures but also improve the structural properties of porous carbon matrix. Profiting from superwettable surface, ultrafine Co-based heterojunctions and large active area, the optimal CoP/CoO_x-HPC catalyst exhibits exceptional bifunctional catalytic activity in 1 M KOH electrolyte, requiring only small overpotentials of 396 and 522 mV for HER and OER, respectively, to achieve a large current density of 400 mA cm⁻². Meanwhile, the assembled alkali-electrolyzer using CoP/CoO_x-HPC as both cathode and anode needs a relatively low voltage of 2.31 V at 400 mA cm⁻², significantly outperforming the commercial couple of Pt/C || RuO₂. This work can be of value in the design of the low-cost and highly active lignin-derived electrocatalysts and also serve as guidance for the high-value utilization of lignin or even other biomass wastes.

Evaluation of potential adsorbents to tackle eutrophication caused by low concentrations of phosphate and ammonium are rarely reported in the literature. Besides, the dynamics/mechanisms for removal of these pollutants at low concentration are yet to be explored. In this study we used five different adsorbents, including La-modified zeolite (LMZ), MgFe-modified biochar (MgFe-BC), phoslock, activated alumina (AA), and diatomaceous earth (DE) to evaluate the removal of these pollutants. Among the selected adsorbents in this study, LMZ and AA both exhibited effective and simultaneous adsorption for phosphate and ammonium and the maximum adsorption capacities were 2.47 mg/g and 3.07 mg/g, respectively. The presence of ${\text{SO}}_4^{2-}$ and ${\text{CO}}_3^{2-}$ negatively impacted phosphate adsorption, while ${\text{Fe}}^{3+}$ and $K^{+}$ ions inhibited ammonium adsorption. LMZ adsorption kinetics was over 3 times faster than other adsorbents within 60 min reaction time. Kinetics studies and isotherms revealed that the removal of phosphate and ammonium was primarily driven by chemical interactions and monolayer adsorption and were better fitted by Langmuir isotherm than the Freundlich isotherm and kinetic study was effectively described by Pseudo-second-order kinetic model. FTIR and XPS analysis revealed that the key mechanisms for phosphate adsorption were electrostatic attraction and inner sphere complexation through ligand exchange, whereas ammonium adsorption was mainly governed by ion exchange. Desorption study revealed that LMZ material was stable after three desorption cycles. This study offers vital knowledge on the nature of adsorption and interactions of potential mesoporous adsorbents with eutrophication-causing pollutants in lakes and rivers and proposes effective remedial mean.

Two hierarchical Y and ZSM5 zeolites were prepared with a surfactant-mediated desilication method. Both the conventional and hierarchical forms were used to prepare NiCu-zeolites via the ion-exchange method. All samples were characterised using different techniques. For the hierarchical materials, N₂ physisorption and TEM analyses confirmed the appearance of mesoporosity. Transition metal-containing zeolites were used as novel electrocatalysts for the glycerol electrochemical oxidation reaction (GEOR) in the form of modified electrodes. Cyclic voltammetry was used to investigate the surface properties of the modified electrodes and their activity toward GEOR at different pH provided by different supporting electrolyte solutions, indicating alkaline conditions as the most promising ones. The hierarchical forms showed a remarkable higher activity compared to the conventional ones, together with appreciable yields towards partially oxidized products of industrial interest. Noteworthy, a stable current higher than 10 mA was generated, which is interesting to produce H₂ by coupling GEOR and hydrogen evolution reaction.