查看更多>>摘要：? 2021Fluorocarbons have commonly been used for refrigerants, coolants, fire-suppressants, propellants, semiconductors, fluoropolymers, and other applications since the early 20th century. However, starting in the late 1980s these chemicals have been highly regulated due to environmental concerns over ozone depletion potential (ODP) and global warming potential (GWP). Porous materials such as zeolites, activated carbons, and metal-organic frameworks (MOFs) are among the current sorbents being studied to reduce emissions of greenhouse gases (GHGs) including fluorocarbons and carbon dioxide. Recent legislation now requires the reduction of hydrofluorocarbon refrigerants over the next two decades to reduce global warming which makes environmental remediation a relevant issue. An extensive literature search has been conducted for fluorocarbon sorption in porous materials to better understand current and prior separation technologies that can reduce climate change. This review article discusses applications for which fluorocarbon sorption is reported and encompasses both academic and patent literature from the late 1940s to present. Pure gas sorption of straight-chain paraffinic and olefinic fluorocarbons as well as zeotropic, azeotropic, and isomeric mixture separations is reviewed. Additional topics including molecular interactions, reactivity, and molecular modeling are discussed in detail.
查看更多>>摘要：? 2021 Elsevier Inc.The preparation of hollow zeolite with a large cavity structure to improve the accessibility to the active sites of catalyst is of great significance. A thin-walled Ti-rich hollow Titanium silicalite-1 (TS-1) Nanobox was synthesized by dissolution-recrystallization using Silicalite-1 (S-1) as the parent zeolite and (NH4)2SO4 as the dual-function crystallization-mediating agent. The wall thickness of the zeolite is about 30 nm, the hollow percentage (the ratio of the cavity area in the middle of the zeolite to the overall area of the zeolite) can reach 0.57, and the Si/Ti ratio is 39.63. The formation mechanism of hollow TS-1 was studied. As the parent zeolite, S-1 is easier to dissolve than TS-1, making it easier for the hollow zeolite to get a complete cavity. When the molar ratio of (NH4)2SO4/TEOS reaches 0.25, the dissolution rate matches the crystallization rate best, and a perfect hollow structure is obtained. The pH of the initial gel is the key factor for the hollow structure. The catalytic activity and stability were tested by 1-hexene epoxidation. The conversion of 1-hexene using HTS-1#S0.25 as the catalyst is much higher than that using hollow TS-1 prepared by the conventional method as the catalyst. HTS-1#S0.25 remains a high oxidation activity and high selectivity after five recycle experiments. In addition, the type of anion also has a great influence on the reactivity. This method can provide a new idea for the preparation of hollow TS-1.
查看更多>>摘要：? 2021 Elsevier Inc.Nanoporous Pt–Co alloys show promising application in chemical catalysis because of low Pt loading, enhanced stability, and high catalytic activity. In this paper, we investigate the tensile mechanical properties of structurally disordered nanoporous Pt–Co alloys via molecular dynamics simulations, emphasizing on the influence of Co atomic concentration. The results demonstrate that alloying could significantly improve the mechanical properties of nanoporous metals (NPMs) and the enhancement of disordered structures is slightly attenuated compared to ordered structures. Similar to conventional NPMs, the dominated plastic deformation of nanoporous Pt–Co alloys is the axial yielding of ligaments. It is found that the Young's modulus and strength of structurally disordered nanoporous Pt–Co alloys are the strongest when the Co atomic concentration is about 24% (at%), indicating an optimum atomic concentration to produce the strongest mechanical properties. The critical value is fairly approximate to the Co concentration in the structurally ordered NP-Pt3Co. In addition to further understanding the mechanical behavior of nanoporous alloys, the study provides a promising strategy for structural design and performance optimization in the application of industrial fields.
查看更多>>摘要：? 2021 Elsevier Inc.X-Ray Fluorescence analysis based on excitation with 109Cd source and registration of characteristic X-rays with Si(Li) detector was used to record the kinetics of desorption of Kr and Xe from carbonaceous samples of 1–100 mg after their treatment with the inert gases at temperatures from 20 to 700 °C. Activated coals with a known pore distribution were used to demonstrate that the Kr desorption half-life is inversely proportional to the square of the pore diameter in the range from 0.7 nm to 50 nm. Although the absorption of Xe was 2–10 times higher in the same pores than the absorption of Kr, the desorption of Xe was about 2.83 times slower than the desorption of Kr. The later fact speaks in favor of using Kr and Ar as a marker for evaluating porous structures rather than Xe.
查看更多>>摘要：? 2021 Elsevier Inc.Methotrexate is one of the commonly used drugs in rheumatology; however, its therapeutic effect has many side effects, so its measurement is crucial. Therefore, a versatile modified electrode based on carbon nano-onion (CNO) and iron oxide nanoparticles functionalized with MCM-41-NH2 was prepared to measure this drug in biological samples. Characterization of the synthesized CNO, functionalized iron oxide nanoparticles, and modified glassy carbon electrodes and their electrochemical performance were studied by infrared spectroscopy, scanning electron microscopy, and X-ray diffraction, electrochemical impedance spectroscopy, and voltammetry techniques. The improvement of the methotrexate oxidation current by modified electrode originated from the increased electrode surface area (0.07 cm2). The detection limit and concentration range of methotrexate measurement were 3 nM, and 0.01–50 μM, respectively. The prepared sensor showed good stability and selectivity for methotrexate measurement in the real samples.
查看更多>>摘要：? 2021 Elsevier Inc.Metal-organic frameworks (MOFs) are potential adsorbents for ammonia capture. However, exploration of high-performing MOFs for ammonia adsorption from humid air is still challenging due to the competitive adsorption between ammonia and water molecules. In this work, high-throughput computational screening of 2932 CoRE MOFs for ammonia capture from humid air was carried out by grand canonical Monte Carlo (GCMC) simulations. It was found that the affinities or Henry's constant of MOFs towards ammonia and water molecules play a more important role in determining the ammonia capture performance than their structural properties. Hydrophobic MOFs exhibited higher ammonia selectivity, while hydrophilic MOFs possessed higher ammonia uptake regardless of the strong adsorption competition from water molecules. The coefficient describing the impacts of water adsorption on ammonia uptake (ICH2O_NH3) revealed that although water adsorption promoted the ammonia uptake in the MOFs with ICH2O_NH3 < 0, their ammonia uptake is still lower than that with ICH2O_NH3 > 0 due to their ultra-low affinity towards ammonia. Moreover, analysis of top performers from screening demonstrated that the competitive adsorption between ammonia and water can be identified by their similar density and potential energy distributions of adsorbed ammonia and water molecules.
查看更多>>摘要：? 2021 Elsevier Inc.Compact and tubular TS-2 zeolite membrane is successfully fabricated on the mullite support by secondary hydrothermal synthesis. The mullite supports are fully covered by the aggregated walnut-shaped TS-2 zeolite crystals, which are the aggregates of fine and rod-shaped crystals and have high BET surface area, total pore capacity and mesoporous volume by advance isothermal characterization. The incorporation of the Ti atoms in framework positions of the MEL zeolite lattice and mainly form tetrahedrally coordinated titanium. Besides, influence of the crystallization temperature and time on the growth and catalytic performance are investigated in this work. The as-synthesized TS-2 zeolite membrane has a good catalytic performance for phenol hydroxylation by hydrogen peroxide. When the reaction temperature and molar ratio of phenol/hydrogen peroxide are 50 °C and 2, the flux, phenol conversion and dihydroxybenzene selectivity of TS-2 zeoite membrane are 6.43 kg m?2 h?1, 32.23% and 99.88%, respectively.
查看更多>>摘要：? 2021 The AuthorsIn the present work, a biosynthesis route for the preparation of hierarchical pompon-like SAPO-34 was developed. Commercially available bacterial cellulose aerogel was used as template. SiO2 loaded bacterial cellulose aerogel was used as silica source and a simple hydrothermal treatment was used for crystallization. XRD, FT-IR, SEM, TEM, N2 adsorption-desorption and TG techniques were employed to characterize the obtained samples. The hierarchical pompon-like SAPO-34 showed a spherical morphology that was comprised of nanosheets with a thickness less than 30 nm. The specific surface area of the hierarchical pompon-like SAPO-34 was 498 m2/g that was higher than the trigonal SAPO-34 crystals of 465 m2/g. The ultrasonic treatment experiment indicated a high stability of the pompon-like structure. In addition, the hierarchical pompon-like SAPO-34 exhibited a CO2 adsorption capacity of 2.26 mmol/g at 100 kPa and 298K and the corresponding CO2/CH4 ideal separation factor was 5.7, which was higher than that of trigonal SAPO-34 crystals. The saturated adsorption capacity and b-value were estimated using single site Langmuir, Toth and Sips adsorption isotherm models and the observed results were constant. Compared with trigonal SAPO-34, hierarchical pompon-like SAPO-34 displayed a higher saturated adsorption capacity, but a lower b-value.
查看更多>>摘要：? 2021 Elsevier Inc.A novel method capable of efficiently predicting the methane adsorption uptakes by metal-organic frameworks (MOFs) is proposed, which is built on the crystal graph convolutional neural network algorithm. Our method considers certain key physical features of MOFs along with information on secondary building units. Because the general force field fails to reproduce methane–MOF interactions involving the open metal site (OMS) adequately, the new force field parameters for methane are refined specifically for the OMS MOFs using a generic algorithm, which is particularly useful in constructing a more accurate dataset via the high-throughput grand canonical Monte Carlo. Extensive analyses demonstrate that the Pearson correlation coefficient and mean average error can reach as high as 0.973 and 9.98 cm3/cm3 for the newly developed algorithm, respectively. Furthermore, this model acquires information from the adsorption volume as embedding representations. This allows for the application of transfer learning by fine-tuning a pretrained graph network for the different properties. Finally, we predicted the methane adsorption volumes by all the MOFs in a 137953 hypothetical database at 298 K and 65 bar within hours. It is believed that this new method could be a useful tool in the early stages of high-throughput virtual screening of novel porous materials for gas adsorption or separation.
查看更多>>摘要：? 2021Pyocyanin is an important virulence factor in the resistance of Pseudomonas aeruginosa to antibiotics. This study evaluated the potential of three clay minerals (smectite, sepiolite, and palygorskite) in binding and degrading pyocyanin. A combination of adsorption experiments, in-situ variable-temperature x-ray diffraction (VTXRD), energy dispersive x-ray spectrometry (EDS), and UV spectroscopy were employed to investigate the (1) adsorption affinity (K) and capacity (Qmax) of clay minerals for pyocyanin, (2) binding sites for adsorption on clay minerals and (3) the degradation/transformation of pyocyanin on clay surfaces. Adsorption experiments were performed at pH3, 4.9, and 7 at which pyocyanin occurred as ～100% protonated, ～50% protonated and zwitterionic, and ～100% zwitterionic species, respectively. Overall, the estimated Qmax was 0.23-0.53 mol/kg for sepiolite, 0.21-0.43 mol/kg for palygorskite, and 0.43-0.68 mol/kg for montmorillonite. The Qmax and K were pH dependent: pH3 < pH7 for sepiolite, pH3 > pH7 for palygorskite, and pH3≈pH4.9>pH7 for montmorillonite. Pyocyanin was mainly adsorbed in the tunnels of sepiolite, external surface of palygorskite, and the interlayer of montmorillonite. The clays did not degrade pyocyanin, instead the structure was slightly transformed on the surfaces of sepiolite and montmorillonite. These results demonstrated the potentials of clay minerals in disarming P. aeruginosa through adsorbing the virulence factor pyocyanin.
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