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Microporous and Mesoporous Materials

Microporous and Mesoporous Materials

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Controlled synthesis of NbO-type metal-organic framework nano/microcrystals with superior capacity and selectivity for dye adsorption from aqueous solution
Zhao-Peng Qi; Yan-Shang Kang; Fan Guo; Wei-Yin Sun;
Abstracts:NbO-type MOF nano/microcrystals were facilely achieved by tuning the volume ratio of DMF and H2O mixed solvent under solvothermal conditions. It was found that NOTT-102 rhombohedral sample obtained with DMF:H2O volume ratio of 15:5 has the largest BET surface area (3006 m2 g−1), compared to the samples with the DMF:H2O volume ratio of 12:8 (2263 m2 g−1) and 20:0 (1962 m2 g−1) as well as the bulk NOTT-102, namely [Cu2(QPTC)] (H4QPTC = [1,1':4′,1″:4″,1‴-quaterphenyl]-3,3‴,5,5‴-tetracarboxylic acid), crystals (2942 m2 g−1). Furthermore, dye adsorption results indicate that NOTT-102 rhombohedral sample exhibits superior adsorption capacity (850 mg g−1) and adsorption selectivity for methylene blue (MB) in contrast to methyl orange, rhodamine B, and acid chrome blue K dyes, which may be one of the promising candidates for potential application in removal of organic dyes from aqueous solution.
Nanostructured carbons modified with nickel as potential novel reversible hydrogen storage materials: Effects of nickel particle size
P.M. Carraro; A.A. García Blanco; G. Lener; D. Barrera; S. Amaya-Roncancio; C. Chanquía; H. Troiani; M.I. Oliva; G.A. Eimer;
Abstracts:In this study, ordered mesoporous carbons CMK-3 were prepared by a nanocasting method using SBA-15 silica as template and sucrose as carbon source. The pure CMK-3 was modified with nickel by wet impregnation method and the effects on hydrogen storage capacity were studied at different pressures and temperatures. The structural, textural and chemical properties were evaluated in order to investigate their correlation with hydrogen adsorption properties. Also, computational methods (DFT) contributed to the understanding of hydrogen storage interactions in the Ni/C samples.
Obtaining high crystalline ball milled H-Y zeolite particles with carbon nanostructures as a damping material
Botagoz Zhuman; Saepurahman; Shaheen Fatima Anis; Raed Hashaikeh;
Abstracts:Nanosized zeolites have attracted interest for many applications including catalysis due to their higher surface area and hence more accessible active sites compared to the microsize zeolite particles. Ball milling is considered as a fast and an efficient technique to reduce the particle size down to nanometer range. However, it is usually accompanied by the formation of large undesired flakes and slabs with a loss of crystallinity and surface area. This study attempts to utilize carbon nanostructures (CNS) as a damping material to overcome the reported drawbacks. The idea of using CNS as a damping material is novel as this is the first study which reports the usage of CNS as damping material that prevents the zeolite micro particles from severe loss in crystallinity compared to the same process without CNS addition. Utilization of CNS gives two-fold advantages pertaining to its flexibility and superior mechanical properties and secondly the ease by which it can be removed off through oxidation after ball milling. Different parameters such as the ball milling solvent and post treatment conditions were varied and studied to observe the changes in final ball milled particle properties, such as morphology, crystallinity index, surface area and particle size distribution. Optimum ball milling and post treatment conditions registered a final zeolite surface area of 1522 m2/g compared to the initial 850 m2/g for micron sized particles. Moreover, x-ray diffraction and high resolution transmission electron microscopy (HR-TEM) images revealed highly crystalline zeolite nano particles with a crystallinity index of 38% which is more than 30% higher than previously reported study of ball milled zeolite particles without any damping material.
Visible light absorption of surface-modified Al2O3 powders: A comparative DFT and experimental study
Vesna Ðorđević; Dušan N. Sredojević; Jasmina Dostanić; Davor Lončarević; S. Phillip Ahrenkiel; Nenad Švrakić; Edward Brothers; Milivoj Belić; Jovan M. Nedeljković;
Abstracts:Surface modification of Al2O3 powders, prepared using reproducible sol-gel synthetic route with small colorless organic molecules, induces charge transfer complex formation and the appearance of absorption in the visible spectral region. Comprehensive microstructural characterization involving transmission electron microscopy, X-ray diffraction analysis, and nitrogen adsorption–desorption isotherms, revealed that γ-crystalline alumina powders consist of mesoporous particles in the size range from 0.1 to 0.3 μm, with specific surface area of 54.8 m2/g, and pore radius between 3 and 4 nm. The attachment of catecholate-type of ligands (catechol, caffeic acid, gallic acid, dopamine and 2,3-dihydroxy naphthalene), salicylate-type of ligands (salicylic acid and 5-amino salicylic acid), and ascorbic acid, to the surface such γ-Al2O3 particles leads to the formation of colored powders and activates their absorption in visible-light spectral region. To the best of our knowledge, similar transformation of an insulator (Al2O3), with the band gap energy of 8.7 eV, into a semiconductor-like hybrid material with tunable optical properties has not been reported in the literature before. The density functional theory (DFT) calculations with periodic boundary conditions were performed in order to estimate the energy gaps of various inorganic/organic hybrids. The calculated values compare well with the experimental data. The good agreement between the calculated and experimentally determined band gaps was found, thus demonstrating predictive ability of the theory when proper model is used.
One-pot synthesis of SiO2‒CeO2 nanoparticle composites with enhanced heat tolerance
Hien Thi Thu Nguyen; Masataka Ohtani; Kazuya Kobiro;
Abstracts:We propose a novel method for the fabrication of CeO2 nanoparticles (NPs) with enhanced heat tolerance. SiO2 was mixed with CeO2 at the nano-level to yield SiO2‒CeO2 NP composites by a solvothermal reaction of precursor solutions consisting of Si(OEt)4, Ce(NO3)3·6H2O, and N,N,N′,N′-tetramethylethylenediamine in methanol. SiO2 content in the SiO2‒CeO2 NP composites was freely controllable by adjusting the Si(OEt)4 mol fraction in range of 0–0.5 in the precursor solutions. With an increase of SiO2 content in the SiO2‒CeO2 NP composites, the primary particle sizes of the CeO2 NPs decreased, and the specific surface areas of the SiO2‒CeO2 NP composites increased remarkably. For SiO2‒CeO2 NP composites obtained from a precursor solution consisting of 1:1 Si(OEt)4 and Ce(NO3)3·6H2O, the specific surface area was over 300 m2/g. Excellent heat tolerance was achieved through the retention of small size of CeO2 crystallites, as well as the large specific surface areas of the SiO2‒CeO2 NP assemblies, even after calcination at 850 °C for 3 h or at 700 °C for 72 h in air.
Carbide-derived carbon obtained via bromination of titanium carbide: Comparative analysis with chlorination and hydrogen storage studies
Sławomir Dyjak; Wojciech Kiciński; Małgorzata Norek; Michał Dyjak; Stanisław Cudziło;
Abstracts:Carbide-derived carbons (CDCs) are synthesized from TiC micropowder via gas phase bromination at the temperature range of 350–1150 °C. The resultant carbon materials demonstrate high specific surface areas and micropore volumes of up to 1745 m2 g−1 and 0.64 cm3 g−1 respectively. Successful bromination of TiC in a wide temperature range permitted the first in-depth comparative study of CDCs produced by Br2 and Cl2 thermochemical extraction. Although minor, some structural differences between TiC-CDCs obtained via bromination and chlorination reactions are observed. It is concluded that it is not the size of halogen and evolving titanium halide molecules but the reactivity of the halogen that affects the microporosity of TiC-CDCs. The structural similarity of materials obtained via Br2 and Cl2 extraction proves that the extractive step does not determine the final structure of CDCs. Cryogenic high-pressure hydrogen storage studies show that the maximum excess hydrogen uptake of TiC-CDCs strongly correlates to the volume of micropores below 1.75 nm in size.
Natural rubber as a template for making hollow silica spheres and their use as antibacterial agents
Wanwisa Kerdlap; Chayut Thongpitak; Sutthinee Keawmaungkom; Chompunuch Warakulwit; Supaporn Klangprapan; Kiattawee Choowongkomon; Yusuf Chisti; Nanthiya Hansupalak;
Abstracts:A method is reported for synthesizing hollow silica spheres (HSS) using skimmed natural rubber (NR) latex as template. Tetraethyl orthosilicate (TEOS) and (3-aminopropyl) triethoxysilane (APTES) were used as the silica source and the co-structure directing agent, respectively. Effects of the TEOS/APTES mole ratio, the synthesis pH, and the total silica content relative to rubber, on HSS formation were observed through transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Skimmed NR latex proved to be a suitable natural template because the rubber particles in it were generally spherical and the ammonia (NH3) conventionally added to the latex as a preservative served as the catalyst for the synthesis of silica. The suitable pH range for forming the hollow structures was 7–10, so long as the TEOS/APTES mole ratio was satisfactory and the total silica available was sufficient. The optimal conditions for forming HSS with robust shells were a TEOS/APTES mole ratio of 1:1, pH 10, and a total silica content of 200 phr. The silver-loaded HSS had excellent antibacterial activity against Escherichia coli.
The synergistic catalytic effect between graphene oxide and three-dimensional ordered mesoporous Co3O4 nanoparticles for low-temperature CO oxidation
Yinshuang Zhao; Fang Dong; Weiliang Han; Haijun Zhao; Zhicheng Tang;
Abstracts:Three-dimensional ordered mesoporous (3D) Co3O4 as a transition metal oxide is widely used in CO catalytic oxidation, and graphene oxide has the abundant oxygen-containing groups and oxygen vacancies which are beneficial to promote the activity of Co3O4-based catalyst. In this paper, the 3D Co3O4/GO catalysts are applied to CO catalytic oxidation reaction and we studied in detail the synergistic effect between 3D Co3O4 and GO. Three dimensionally ordered mesoporous Co3O4/GO (3D Co3O4/GO) catalysts are prepared by solvothermal method. The addition of graphene oxide obviously increased the specific surface area and promoted the dispersion of active metal. The oxygen-containing groups on the surface of graphene oxide increase the reactive sites simultaneously. The synergistic effect of graphene oxide and Co3O4 made the 3D Co3O4/GO catalyst showed excellent catalytic activity. Moreover, the influence of solvent (water, ethanol, ethylene glycol) was studied. The results showed that the change of the solvent did not affect the structure of the metal oxide, but affected the chemical state of the metal and the concentration of oxygen-containing functional groups on the surface of catalyst.
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