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  First | 1 2 3 4 5 6 7 | Last

Microporous and Mesoporous Materials    [5 followers]  Follow    
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 1387-1811
     Published by Elsevier Homepage  [2556 journals]   [SJR: 1.306]   [H-I: 93]
  • Effect of steaming on acidity and catalytic performance of H-ZSM-5 and
           P/H-ZSM-5 as naphtha to olefin catalysts
    • Abstract: Publication date: April 2014
      Source:Microporous and Mesoporous Materials, Volume 188
      Author(s): Kohei Kubo , Hajime Iida , Seitaro Namba , Akira Igarashi
      The effect of steaming on the acidity and catalytic performance of H-ZSM-5 zeolites with various Si/Al atomic ratios and P/H-ZSM-5 as naphtha cracking catalysts to produce light olefin were investigated. The acid amount of H-ZSM-5(Si/Al atomic ratio=51) was monotonously decreased with the steaming time at 873K. However, the catalytic activity of H-ZSM-5(51) for heptane cracking was enhanced by the steaming for short times (∼0.5h). The activation energy for H-ZSM-5(51) steamed for 0.5h was lower than that for the parent H-ZSM-5(51). Moreover, the catalytic activity of H-ZSM-5(51) for cracking of cumene, from which the Brønsted acidity can be evaluated, was enhanced by the steaming for a short time of 0.5h. From these results, the stronger Brønsted acid sites might be generated by the steaming for short times, resulting in the enhancement in the catalytic activity for cracking of heptane. The catalytic activity of H-ZSM-5(51) for cracking of heptane considerably decreased after the steaming for long times. On the other hand, only a little decrease in the rate constant for cracking of heptane over H-ZSM-5(200) by the steaming for long times was observed. These findings suggest that the high silica H-ZSM-5 as H-ZSM-5(200) may have a high percentage of aluminum atoms which is highly resistant to the dealumination by the steaming. The catalytic activity for cracking of heptane over P/H-ZSM-5(51) was also enhanced by the steaming for a short time. The P/H-ZSM-5(51) steamed for 10h exhibited a much higher activity than the H-ZSM-5(51) steamed for 10h. These results indicate that the phosphorus impregnation greatly suppresses the dealumination of H-ZSM-5.
      Graphical abstract image

      PubDate: 2014-01-23T10:20:32Z
       
  • Methane storage in zeolite-like carbon materials
    • Abstract: Publication date: April 2014
      Source:Microporous and Mesoporous Materials, Volume 188
      Author(s): Myrsini K. Antoniou , Evmorfia K. Diamanti , Apostolos Enotiadis , Alfonso Policicchio , Konstantinos Dimos , Federica Ciuchi , Enrico Maccallini , Dimitrios Gournis , Raffaele G. Agostino
      High specific surface area zeolite-like carbon materials (CZ) were synthesized by combining the hard template method with the Chemical Vapor Deposition (CVD), using zeolite beta as solid template and acetylene as carbon precursor, at different reaction temperatures (1023, 1073 and 1123K). CZ materials were characterized by X-ray diffraction, Scanning Electron Microscopy and nitrogen adsorption–desorption measurements. The nanoporous CZ materials possess surface areas up to 1130m2/g and total pore volumes up to 0.75mL/g while XRD data and SEM images show the successful replication of the structure and morphology of the zeolite particles into the final carbon materials. Methane storage properties at different temperatures (287, 298 and 313K) have been investigated by Sievert’s-type apparatus up to 3.5MPa. The CZ materials exhibit a high and reversible methane storage capacity, with measured gravimetric uptake up to 8.0wt% at 298K and 3.5MPa, a much higher value compared to the pristine zeolite beta which shows gravimetric methane adsorption capacity up to 1.5wt% at the same conditions. The analysis of the obtained isotherm curves by Tόth model shows the same grade of homogeneity on sample porosity for all probed samples while the evaluation of the adsorption enthalpy at low pressures reveals a similar binding energy between the methane molecules and the samples’ surfaces despite of their different long range order.
      Graphical abstract image

      PubDate: 2014-01-23T10:20:32Z
       
  • Double-doped zeolites for corrosion protection of aluminium alloys
    • Abstract: Publication date: April 2014
      Source:Microporous and Mesoporous Materials, Volume 188
      Author(s): Emmanuel L. Ferrer , Analiza P. Rollon , Herman D. Mendoza , Ugo Lafont , Santiago J. Garcia
      This work has introduced a new doping concept to develop self-healing anticorrosive coatings by synergistic and controlled release of corrosion inhibitors. NaY zeolites were double doped in a two-step process with cerium and diethyldithiocarbamate (DEDTC) as these are known efficient corrosion inhibitors for AA2024-T3. The corrosion efficiency and mechanisms were evaluated by a combination of optical, analytical and electrochemical techniques. It was observed that the inhibitors deposit on the metallic surface with preference for intermetallic particles. Current density measurements of the samples revealed that the double doped NaY zeolite was able to provide both immediate and sustained corrosion protection for the alloy substrate. Moreover, impedance analysis of hybrid sol–gel coatings with 10% wt. of the most relevant doped zeolites revealed distinctive release events from the coatings containing the doped zeolites. The results confirm the potential of this double doping concept which can be extrapolated to other carriers and inhibitors for an effective environmentally friendly active corrosion protection. It is believed that the double doping concept can be extrapolated to fields other than corrosion protection.
      Graphical abstract image

      PubDate: 2014-01-23T10:20:32Z
       
  • Synthesis of mesostructured stishovite from FDU-12/carbon composite
    • Abstract: Publication date: 15 March 2014
      Source:Microporous and Mesoporous Materials, Volume 187
      Author(s): V. Stagno , M. Mandal , W. Yang , C. Ji , Y. Fei , H.-K. Mao , K. Landskron
      Nanocasting at high pressure has been recently proposed as a novel strategy for the synthesis of periodic mesoporous materials with crystalline walls. In this study we present results on the synthesis of mesostructured stishovite from mesostructured FDU-12/carbon composite precursor using the multi-anvil press. Results from quenched experiments performed at a pressure of 14GPa indicate that a minimum temperature of 500°C is needed to crystallize stishovite from the amorphous silica precursor with a preserved mesostructure. Transmission electron microscopy combined with small angle X-ray scattering measurements confirmed the mesostructure of synthetic stishovite having carbon-filled pores with a diameter of ∼19nm similar to the pore size of the FDU-12 precursor. Calcination of the stishovite/carbon composite at 450°C in air at ambient condition leads to amorphization of the stishovite. Our results show that mesostructure materials can be synthesized at very high pressures without loss or critical modification of the mesostructure.
      Graphical abstract image Highlights

      PubDate: 2014-01-23T10:20:32Z
       
  • [M]-CAL-2: MeAPSO-34-like molecular sieves using a lamellar
           aluminophosphate as precursor
    • Abstract: Publication date: 15 March 2014
      Source:Microporous and Mesoporous Materials, Volume 187
      Author(s): Mathias Strauss , Gesley Alex Veloso Martins , Gloria Berlier , Salvatore Coluccia , Leonardo Marchese , Heloise O. Pastore
      [M]-CAL-2 (M=Mn, Co and Fe) are metallosilicoaluminophosphates ([M]-APSO) with chabazite-related structure, which are part of the CAL molecular sieves family. They were prepared with a recently developed synthesis based on the use of layered AlPO precursor. The used procedure allowed to obtain high loadings of metal ions and to control the morphology of the crystals. The materials were characterized by structural techniques such as X-ray diffraction, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), thermogravimetry (TGA), and spectroscopic techniques such as UV–Vis and Fourier transformed Infrared (FTIR) with particular attention to the study of their redox functionalities. The results show that [M]-CAL-2 crystals presented rhombohedra morphology and the particles sizes are dependent of the metal concentration in the precursor gel, in addition these particles have a lamellar memory originated from the layered AlPO precursor. The FTIR, UV–Vis and elemental results supported the presence of transition metal ions on the framework of the synthesized materials and allowed to envisage the dependency of the metal and silicon concentrations on a Lowenstein-like ruled substitution mechanism. Finally, the reversible redox behavior of the materials was studied by in situ UV–Vis-NIR spectroscopy. This aspect together with the already shown acidity of CAL samples allowed confirming the acid and redox bifunctionality of the obtained molecular sieves, which can thus be proposed for catalytic applications.
      Graphical abstract image Highlights

      PubDate: 2014-01-23T10:20:32Z
       
  • CO2 adsorption on APTES functionalized mesocellular foams obtained from
           mesoporous silicas
    • Abstract: Publication date: 15 March 2014
      Source:Microporous and Mesoporous Materials, Volume 187
      Author(s): E. Vilarrasa-García , J.A. Cecilia , S.M.L. Santos , C.L. Cavalcante Jr. , J. Jiménez-Jiménez , D.C.S. Azevedo , E. Rodríguez-Castellón
      The CO2 adsorption capacity of different APTES-grafted mesoporous silicas of SBA-15 type has been investigated and the influence of support textural properties and the role of the presence of silanol groups on the adsorption capacity are analyzed. Four adsorbents based on SBA-15 were prepared using tetraethyl orthosilicate (TEOS) as silicon source, with and without the addition of trimethyl-benzene (TMB) and n-heptane as swelling agents, and adding in some cases ammonium fluoride as a solubility enhancer. 3-(triethoxysilyl)propylamine (APTES) was then used as grafting agent by reaction with free silanol groups on the silica surface so as to provide pending amino groups for CO2 capture. The adsorption behavior for all supports was adequately described by a Freundlich model, whereas for the APTES-grafted silica, a dual-site Langmuir model was applied, which allowed us to quantify and qualify two different adsorption sites. The addition of n-heptane as swelling agent led to pore sizes beyond 10nm and improved significantly the grafting efficiency, leading to higher CO2 uptakes as compared to the starting supports. At 1bar and 25°C and anhydrous conditions, CO2 uptakes of 2.4mmolg−1 or 0.64mol CO2 per molN were achieved (which reveals a significant contribution of physisorption). This sample could be successfully regenerated at 100°C, maintaining a constant capacity for 3 adsorption–desorption cycles. At 0.15bar and 60°C, anhydrous conditions, CO2 uptake reaches 1.5mmolg−1. This value may be theoretically doubled in the presence of humidity, and there is room for further improvement if supports with the same pore size (13nm) and higher surface areas (e.g. 1000m2/g) are successfully synthesized.
      Graphical abstract image Highlights CO2 adsorption/desorption isotherms on HTT34 for the first (squares), second (triangles) and third (circles) adsorption/desorption cycles at 25°C. Desorption branches are highlighted by empty symbols.

      PubDate: 2014-01-23T10:20:32Z
       
  • Hierarchical porous zeolite ZSM-58 derived by desilication and
           desilication re-assembly
    • Abstract: Publication date: 15 March 2014
      Source:Microporous and Mesoporous Materials, Volume 187
      Author(s): Tim Biemelt , Carolin Selzer , Franz Schmidt , Giovanni Mondin , Andreas Seifert , Katja Pinkert , Stefan Spange , Thomas Gemming , Stefan Kaskel
      Hierarchical porosity in zeolite ZSM-58 was achieved by desilication with pure solutions of NaOH and mixtures of NaOH and cetyltrimethylammonium bromide (CTAB) in a desilication and desilication re-assembly process. The resulting ZSM-58 samples were investigated concerning their chemical and textural structure by means of transmission and scanning electron microscopy, X-ray diffraction, nitrogen and argon physisorption, elemental analyses, 27Al and 29Si solid-state magic angle spinning nuclear magnetic resonance spectroscopy, and temperature programmed desorption of ammonia. In the case of applying pure NaOH solutions on Si/Al ratios of Si/Al=50 rather macroporous zeolite ZSM-58 with broad pore size distribution was obtained and pore volume depended on the sodium hydroxide concentration. Higher Si/Al ratios did not result in any additional porosity. Adding CTAB to the desilication solution lead to hierarchical ZSM-58 materials with narrow additional pores in the range of 3–4nm resulting from an amorphous layer on the surface of the ZSM-58 crystals that was long range ordered for intermediate NaOH concentrations independent from the initially deployed Si/Al ratio. The total specific surface area of such materials was as high as 868m2 g−1 with high values of external specific surface area and simultaneously the desilication yield could be increased due to the re-assembly of dissolved silica species. Therefore, high values for the hierarchy factor and desilication efficiency could be achieved. The amount of strong acid sites of the desilicated samples decreased with increasing NaOH concentration because of the generation of silanol groups, pentahedral, and octahedral coordinated extra framework aluminum.
      Graphical abstract image

      PubDate: 2014-01-23T10:20:32Z
       
  • A simple one pot synthesis of mesoporous silica hosted silver catalyst and
           its low-temperature CO oxidation
    • Abstract: Publication date: April 2014
      Source:Microporous and Mesoporous Materials, Volume 188
      Author(s): Zhenping Qu , Xiaodong Zhang , Fangli Yu , Jingxuan Jia
      A novel and simple one pot synthesis approach using dodecylamine (DDA) as capping agent and structure director has been employed to synthesize the silica-supported Ag nanoparticles. The catalysts were characterized by XRD, N2 adsorption–desorption isotherms, TEM and TG-DTA. It was found that the loading and particle size of Ag were strongly related to the surfactant DDA. In addition, the formed local reductive environmental due to the decomposition of DDA during thermal treatment procedure could prevent the aggregation of Ag nanoparticles and be benefit for the formation of uniformly dispersed Ag nanoparticles on the HMS support (1.5–4.5nm). The excellent catalytic activity for CO oxidation (T98(CO)=20°C) demonstrated that the method was effective for synthesizing the highly dispersed nano-silver catalyst.
      Graphical abstract image Highlights

      PubDate: 2014-01-23T10:20:32Z
       
  • Binary adsorption of CO2/CH4 in binderless beads of 13X zeolite
    • Abstract: Publication date: 15 March 2014
      Source:Microporous and Mesoporous Materials, Volume 187
      Author(s): José A.C. Silva , Adelino F. Cunha , Kristin Schumann , Alírio E. Rodrigues
      The binary sorption CO2 and CH4 in binderless beads of 13X zeolite has been investigated between 313 and 473K and total pressure up to 5atm through fixed bed adsorption experiments. The amount adsorbed of CO2 and CH4 is around 4.7mmol/gads and 0.4mmol/gads, respectively, at 313K and 3.7atm in a 50/50equimolar mixture. In a 25(CO2)/75(CH4) mixture the amount adsorbed is 4.0 and 0.84mmol/g at the same temperature and pressure. Experimental selectivities CO2/CH4 range from 37 at a low pressure of 0.667atm to approximately 5 at the high temperature of 423K. Comparing these values with the ones in literature CO2 adsorption capacity is 20% higher than in CECA 13X binder pellets. The CO2/CH4 binary isotherms were fitted with the extended Fowler model that takes into account interaction between adsorbed molecules at adjacent sites suggesting a moderate attraction between CO2 and CH4. The model is validated through a graphical method using the single component isotherm parameters. The breakthrough curves measured show a plateau of pure CH4 of approximately 6min depending of the operating conditions chosen.
      Graphical abstract image

      PubDate: 2014-01-15T13:41:18Z
       
  • Chiral Ir(I) complex supported on external surface passivated SBA-15 as
           heterogeneous catalyst for asymmetric transfer hydrogenation of aromatic
           ketones
    • Abstract: Publication date: 15 March 2014
      Source:Microporous and Mesoporous Materials, Volume 187
      Author(s): Lan-Lan Lou , Huanling Du , Yanbin Shen , Kai Yu , Wenjun Yu , Qiu Chen , Shuangxi Liu
      Chiral 9-amino epi-cinchonine was anchored on external surface passivated SBA-15 as well as calcined SBA-15. The two resulting materials were used as catalysts for the asymmetric transfer hydrogenation of aromatic ketones after complexing with [Ir(COD)Cl]2. Higher enantioselectivities were obtained over the passivated SBA-15 supported catalyst compared with the catalyst based on calcined SBA-15 as well as the homogeneous counterpart. Especially for the substrate of acetophenone, an obviously high enantiomeric excess (ee) of 74% (homogeneous ee: 60%) was achieved with comparable conversion to the homogeneous catalyst (97% vs. 98%). Furthermore, the passivated SBA-15 supported catalyst demonstrated higher stability during the asymmetric transfer hydrogenation reaction as compared with the catalyst based on calcined SBA-15.
      Graphical abstract image

      PubDate: 2014-01-15T13:41:18Z
       
  • Porous organic–inorganic hybrid aerogels based on bridging
           acetylacetonate
    • Abstract: Publication date: 15 March 2014
      Source:Microporous and Mesoporous Materials, Volume 187
      Author(s): Qiuli Yang , Xin Tan , Sujuan Wang , Jianyong Zhang , Liuping Chen , Jie-Peng Zhang , Cheng-Yong Su
      Organic–inorganic hybrid aerogels are receiving growing attention due to their high tuneability. In this contribution a novel type of organic–inorganic hybrid aerogels with high micro- and mesoporosity have been prepared successfully from a bridging bis(acetylacetonate) ligand, 3,4-diacetyl-2,5-dioxohexane, and trivalent metal ions (Al3+ and Cr3+). The metal-acetylacetonate aerogels compose of nanoscale metal-organic particles, which aggregate to form the gel matrix. N2 sorption shows that the aerogels have high BET surface areas up to ∼1100m2 g−1 and hierarchical porosity. The porosity can be altered by introducing of second divalent metal ions into the aerogel. The aerogels show ability to adsorb various gases (H2, CO2 and CH4) and vapors (MeOH and EtOH). Water sorption measurements reveal that the aerogels have relatively hydrophobic pore surface.
      Graphical abstract image Highlights

      PubDate: 2014-01-15T13:41:18Z
       
  • Editorial Board
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186




      PubDate: 2014-01-11T16:55:17Z
       
  • Synthesis, structure and property of Ni(II) coordination polymers with
           mixed dicarboxylate and benzoimidazol-containing ligands
    • Abstract: Publication date: 15 March 2014
      Source:Microporous and Mesoporous Materials, Volume 187
      Author(s): Ling-Ling Zhai , Yue Zhao , Li Luo , Peng Wang , Qing Liu , Kai Chen , Wei-Yin Sun
      Four new Ni(II) complexes [Ni(L)(SO4)(H2O)2]·H2O (1), [Ni3(L)4(p-BDC)3(H2O)6]·6H2O (2), [Ni(L)(m-BDC)(H2O)2]·0.5H2O (3) and [Ni(L)(BPDC)(H2O)2] (4) have been prepared by reactions of 3,5-di(1H-benzimidazol-1-yl)pyridine (L) with nickel sulfate in the presence of auxiliary ligands of phthalic acid (o-H2BDC), terephthalic acid (p-H2BDC), isophthalic acid (m-H2BDC) and biphenyl-4,4′-dicarboxylic acid (H2BPDC), respectively. Interestingly, phthalate (o-BDC2−) did not take part in formation of 1, instead SO 4 2 - was found in 1. Complex 2 with p-BDC2− shows different two-dimensional (2D) network from 1 while 3 has one-dimensional (1D) chain structure. Complex 4 is a three-dimensional (3D) framework with CdSO4 topology. The thermal stability and adsorption property of the complexes were investigated. Furthermore, it was found that complexes 1–4 can catalyze acetalization reaction of aldehydes with methanol, and 1 gives the highest yield.
      Graphical abstract image

      PubDate: 2014-01-08T01:53:51Z
       
  • The dielectric response of low-k interlayer dielectric material
           characterized by electron energy loss spectroscopy
    • Abstract: Publication date: 15 March 2014
      Source:Microporous and Mesoporous Materials, Volume 187
      Author(s): Pradeep K. Singh , Jan M. Knaup , Sven Zimmermann , Steffen Schulze , Stefan E. Schulz , Thomas Frauenheim , Michael Hietschold
      In this study, the dielectric response of low-k dielectric materials has been characterized by electron energy loss spectroscopy. A widely accepted fast Fourier transform based Kramers–Kronig method (Johnson, 1975) [3] has been used to derive the high-frequency response of these materials. We used three different low-k dielectric materials to find out the effect of porosity and carbon content on the dielectric response of materials. Amorphous SiO2 and SiC:H samples are used for comparison. All samples were deposited by plasma-enhanced chemical vapor deposition technique. A Lorentzian-based oscillator model has been used to determine the eigen-energy of excitations by fitting the measured loss function. The model is specially designed to let all oscillator parameters move freely and find their most probable position by using a least square fitting analysis procedure. The band gap for amorphous SiO2 which corresponds to the first absorption peak in the imaginary part of dielectric function is found to be at around 9eV. We observed that in the case of dense low-k material, there appears a finite density of states (DOS) inside the band gap of SiO2, whereas the inclusion of porosity into dense low-k network diminishes the in-gap DOS and widens the band gap to around 10eV.
      Graphical abstract image

      PubDate: 2014-01-08T01:53:51Z
       
  • Interactions between biomolecules and an iron-silica surface
    • Abstract: Publication date: 15 March 2014
      Source:Microporous and Mesoporous Materials, Volume 187
      Author(s): Rebecca J. Desch , Jungseung Kim , Stephen W. Thiel
      An iron-silica adsorbent (1:1 ratio by mass) with a pore cell size of 11.4nm and BET surface area of 610m2 g−1 was synthesized and compared to a mesocellular foam (MCF) silica and iron oxide for amino acid (alanine, aspartic acid, lysine and histidine) and lysozyme adsorption. Amino acid batch adsorption loadings did not exceed estimated monolayer coverage and were generally quantitatively similar on iron-silica and MCF silica; the observed loadings followed the trend alanine>lysine/aspartic acid≫histidine. Multilayers were observed on the strongly positive iron oxide surface. The dynamic heat of biomolecule adsorption was directly measured with flow microcalorimetry (FMC); the enthalpies of adsorption of alanine, aspartic acid, lysine, and histidine on iron-silica were −0.046, −0.73, −5.3 and −14.3kJmol−1, respectively. Alanine adsorption was mediated by the surrounding water, aspartic acid adsorbed through weak electrostatic attractions, and lysine and histidine formed bonds during adsorption. Lysozyme monolayer loading was higher on iron-silica than on MCF silica, calorimetric studies indicate a different lysozyme adsorption mechanism on iron-silica and MCF silica.
      Graphical abstract image

      PubDate: 2014-01-04T01:38:04Z
       
  • Formation mechanism of porous silicon nanowires in HF/AgNO3 solution
    • Abstract: Publication date: 15 March 2014
      Source:Microporous and Mesoporous Materials, Volume 187
      Author(s): N. Bachtouli , S. Aouida , B. Bessais
      This paper reports on the features of silicon nanowires (SiNWs) formed by metal-assisted chemical etching of crystalline silicon in AgNO3-based chemical solutions. Scanning electron microscopy (SEM) shows that the SiNWs may have different structures and porosities depending on the preparation conditions. Porous SiNWs reduce the surface effective reflectivity to less than 3% in the UV-blue spectral region. Although it was commonly reported that preferential etching is performed along Si 〈100〉 orientations, we found that SiNWs can grow along several directions depending on the oxidant (AgNO3) concentration. We show that the reaction mechanism leading to the formation of the SiNWs is principally governed by redox charge transfer in HF/AgNO3 solutions. However, the formation of porous SiNWs was found to decrease the minority carrier lifetime, which is in turn problematic to achieve high efficiency silicon solar cells.
      Graphical abstract image

      PubDate: 2014-01-04T01:38:04Z
       
  • Experimental energetics of large and extra-large pore zeolites: Pure
           silica beta polymorph C (BEC) and Ge-containing ITQ-33
    • Abstract: Publication date: 15 March 2014
      Source:Microporous and Mesoporous Materials, Volume 187
      Author(s): L. Wu , J. Hughes , M. Moliner , A. Navrotsky , A. Corma
      The enthalpies of formation of the large pore pure silica beta polymorph C (BEC) and the extra-large pore germanosilicate ITQ-33 zeolite are investigated by high temperature oxide melt solution calorimetry. The enthalpies of formation from quartz for two BECs synthesized with different organic structure directing agents, SDA1 and SDA9 differ by 4kJ/mol. The two SDAs produce phases with different properties as well as different energetics for the same framework and composition, due to the different amount of structural defects, while the more defective BEC is energetically less stable by 4kJ/mol. The enthalpy of formation of defect-free pure silica BEC agrees with the predicted value proposed several years ago. Moreover, the enthalpy of formation of ITQ-33 (Ge/(Ge+Si)=0.3) supports the energetic trends seen previously, namely that the enthalpy of formation becomes more endothermic as the content of double four rings (D4R) increases. The previous trend of energetics of porous materials versus molar volume is supported by the present data, with a diminishing destabilization for very open structures.
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      PubDate: 2014-01-04T01:38:04Z
       
  • Synthesis of colloidal silicalite-1 at high temperatures
    • Abstract: Publication date: 15 March 2014
      Source:Microporous and Mesoporous Materials, Volume 187
      Author(s): Tayyabah Butt , Lubomira Tosheva
      Stable colloidal suspensions of silicalite-1 were prepared by hydrothermal treatment of clear precursor suspensions at high temperatures, 150 and 170°C. The precursor suspensions were pretreated prior to hydrothermal treatment. Different pretreatment procedures were applied, namely ultrasonic treatment or heating at 45–60°C, for different periods of time. In all cases, the size of the crystals decreased with increasing the time of pretreatment. The pretreatment procedure was found to influence the behavior of the tetrapropylammonium hydroxide solution used as structure-directing template during hydrothermal treatment. Colloidal stability of pretreated samples was improved compared to samples prepared by direct hydrothermal treatment.
      Graphical abstract image

      PubDate: 2014-01-04T01:38:04Z
       
  • Adsorption removal of organic dyes on covalent triazine framework (CTF)
    • Abstract: Publication date: 15 March 2014
      Source:Microporous and Mesoporous Materials, Volume 187
      Author(s): Tao Wang , Kamalakannan Kailasam , Ping Xiao , Guoshen Chen , Lianqing Chen , Lihua Wang , Jinlin Li , Junjiang Zhu
      Covalent triazine framework (CTF) with microporous structure and high surface area are synthesized and used as adsorbent for adsorption removal of organic dyes in aqueous solution. It shows adsorption capacity of 1.01mmol/g for Rhodamine B (RhB), which is far higher than that reported for traditional adsorbents such as activated carbon (AC), which shows adsorption capacity of 0.36mmol/g for RhB under otherwise identical conditions. Within 55min the material shows uptake of 0.48mmol/g for RhB at weight ratio of RhB/CTF=0.24, and the initial pH can be adjusted in a wide range, from 1 to 11, without significantly affecting the uptake. Further studies indicate that the CTF can be regenerated and no appreciable loss in the uptake of RhB is observable even after four cycles. Mechanism and kinetic investigations indicate that the adsorption of RhB onto CTF obeys the Langmuir isothermal adsorption model with pseudo-second-order equation. Besides, the CTF is also applicable to adsorption removal of other organic dyes including reactive brilliant red X-3B and direct scarlet 4BS, with uptake of 0.43mmol/g for X-3B and 0.18mmol/g for 4BS within 55min.
      Graphical abstract image

      PubDate: 2014-01-04T01:38:04Z
       
  • Bioinspired hybrid mesoporous silica–gelatin sandwich construct for
           bone tissue engineering
    • Abstract: Publication date: 15 March 2014
      Source:Microporous and Mesoporous Materials, Volume 187
      Author(s): RanjithKumar Ravichandran , Dhakshinamoorthy Sundaramurthi , Sakthivel Gandhi , Swaminathan Sethuraman , Uma Maheswari Krishnan
      Mesoporous materials possessing pore sizes in the range 2–50nm and surface reactive functionalities have elicited immense interest due to their exciting prospects in bone tissue engineering. Fabricating these mesoporous materials as continuous fibers adds an additional feature, which can be exploited for biomedical applications especially in tissue engineering. Though there are several factors involved in the remodeling of a damaged tissue, the design of scaffold plays an important role in tissue remodeling. The present work reports the fabrication of a bioinspired 3-D sandwich construct of mesoporous silica fibers and gelatin for bone tissue engineering. The silica nanofiber mesh and the gelatin gel mimic the collagen network and the glycosaminoglycan gel in the native extracellular matrix. Tetraethyl orthosilicate, polyvinyl pyrrolidone (PVP) and the tri-block copolymer P-123 were electrospun to fabricate continuous ordered mesoporous silica nanofibers by optimizing solution and process parameters. The 3-D scaffolds offered a suitable microenvironment for cell infiltration and tissue in-growth. The bioactivity of mesoporous silica fiber along with 2-D gelatin film was found to promote viability of human osteoblast-like cells (MG63) and alkaline phosphatase activity. Gene expression profiles of collagen I, alkaline phosphatase, osteocalcin, osteopontin and bone sialoprotein indicated good osteoblast proliferation, maturation and infiltration on the sandwich constructs. This novel silica–gelatin 3-D scaffold possesses promising characteristics for enhanced bone tissue regeneration.
      Graphical abstract image

      PubDate: 2014-01-04T01:38:04Z
       
  • Interpretation of net and excess adsorption isotherms in microporous
           adsorbents
    • Abstract: Publication date: 15 March 2014
      Source:Microporous and Mesoporous Materials, Volume 187
      Author(s): Ronny Pini
      Adsorption data are routinely reported as net or excess amounts adsorbed; although measuring techniques are nowadays well established, the interpretation and further use of these two measures is limited by the uncertainty on the estimated internal pore volume of the material and, accordingly, the volume (or density) of the adsorbed fluid. In this study, adsorption data are presented that have been measured with CO2 on 13X zeolite in both crystal and pellet forms at 50°C and in the pressure range 0.02–14MPa by using a magnetic suspension balance. The adsorbents’ structural parameters have been obtained through a combination of independent measuring techniques, including low-pressure adsorption and mercury intrusion porosimetry, and a methodology is presented where both net and excess adsorption isotherms are simultaneously evaluated through a graphical method. While providing additional insights on the meaning of these two different frameworks, the application of such an integrated approach allows for a more consistent interpretation of the obtained adsorption data. It is shown that for both materials the adsorption process is entirely controlled by the filling of the micropores and that the adsorbent’s volume is overestimated when helium is used as a probing gas. The statistical adsorption isotherm model proposed by Ruthven is applied to describe the measured adsorption isotherms and provides a much better fit than the Langmuir model. For both crystals and pellets, and over the whole pressure range, CO2 adsorbs as a dense liquid with density values starting from the critical density of the fluid and reaching ∼ 27mol/L (i.e. 15 molecules/cage) at the highest pressure of the experiment.
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      PubDate: 2014-01-04T01:38:04Z
       
  • Mesoporous iron phosphate/phosphonate hybrid materials
    • Abstract: Publication date: 15 March 2014
      Source:Microporous and Mesoporous Materials, Volume 187
      Author(s): Jamal El Haskouri , Alaina Moragues , Aurelio Beltrán , Sonia Murcia-Mascarós , Fernando Plazaola , Estibaliz Legarra , Adela Mauri-Aucejo , Mauro Brotons-Gisbert , Juan F. Sánchez-Royo , Daniel Beltrán , Pedro Amorós
      Relatively high surface area pure mesoporous iron-phosphorus oxide-based derivatives have been synthesized through an S+I− surfactant-assisted cooperative mechanism by means of a one-pot preparative procedure from aqueous solution and starting from iron atrane complexes and phosphoric and phosphonic acids. A soft chemical extraction procedure allows opening the pore system of the parent as-prepared materials by exchanging the surfactant without mesostructure collapse. The nature of the pore wall can be modulated from iron phosphate up to hybrids involving approximately 30% of organophosphorus entities (phosphonates or diphosphonates). X-ray powder diffraction, transmission electron microscopy and surface analysis techniques show that these hybrid materials present regular unimodal disordered pore systems. Spectroscopic results (Fe-57Mössbauer, XPS, UV–vis, FTIR and Raman) not only confirm the incorporation of organophosphorus entities into the framework of these materials but also provide us useful information to elucidate both the mechanism through which they are formed, and some details on their specific local structures.
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      PubDate: 2014-01-04T01:38:04Z
       
  • A new route of synthesis of Na-Mica-4 from sodalite
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Moisés Naranjo , Miguel A. Castro , Agustín Cota , Esperanza Pavón , M. Carolina Pazos , María D. Alba
      Synthesis of Na-Mica-4 has been achieved by a “mix and calcine” method using sodalite and magnesium fluoride as the only precursors. Previous research found sodalite as a key intermediate reaction product in the formation of Na-Mica-4 when the NaCl melt method was employed. Similarities in structure, chemical composition and cation distribution in products using the proposed method and the NaCl melt method are described and suggest that Na-Mica-4 is a very stable product. The use of sodalite as precursor provokes microporous formation in the final mica. The absence of excess Na leads to a lower particle size and to the presence of less impurity in the calcined product. Different sodalites could be used in the synthesis of different Na-Mica-4 with presumably different physicochemical properties.
      Graphical abstract image Highlights

      PubDate: 2013-12-31T01:08:58Z
       
  • Dependency of the formation of Au-stabilized nanoporous copper on the
           dealloying temperature
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Zhenhua Dan , Fengxiang Qin , Yu Sugawara , Izumi Muto , Nobuyoshi Hara
      Au-stabilized nanoporous Cu with a pore size of 7–24nm was fabricated through the dealloying of amorphous Ti60Cu40− x Au x alloys (x =1, 2at%) in HF solutions at 298, 323 and 348K. Nanoporous structures with larger sizes of bi-continuous pore-to-ligament were obtained at higher temperatures. The residue was confirmed to be crystalline fcc Au and a Cu–Au solid solution. The surface diffusivity of Cu adatoms decreased more than 4 orders of magnitude due to the involvement of Au atoms as the temperature decreased. The surface diffusivity had a linear dependence on the reciprocal of the temperature, in accordance with the Arrhenius law. The activation energy of surface diffusion for amorphous TiCuAu alloys was estimated to be 56.1–62.7kJmol−1, which was independent of the Au content and the concentration of the HF solutions.
      Graphical abstract image Highlights

      PubDate: 2013-12-31T01:08:58Z
       
  • High photocatalytic and adsorptive performance of anatase-covered titanate
           nanotubes prepared by wet chemical reaction
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Wen Liu , Alistair G.L. Borthwick , Xuezhao Li , Jinren Ni
      Anatase-covered titanate nanotubes (TiNTs) with high photocatalytic and adsorptive performance characteristics were prepared through wet chemical reaction. TEM and XRD analysis revealed that the morphology and composition of the modified TiNTs were directly related to the ambient pH and temperature conditions of the reaction. Lower pH and higher temperature tended to enhance the transition from titanate to anatase; moreover, the transition process involved an in situ rearrangement of the primary structural unit [TiO6]. The photocatalytic performance of modified TiNTs depended on the amount of TiO2 transformed from titanate, whereas the adsorptive property was primarily determined by the tubular titanate structure. TiNTs modified under optimal conditions of pH 2 and 120°C (TiNTs-120-2) not only exhibited high photocatalytic degradation rate for methyl orange (0.568×10−2 min−1), but also possessed a considerable capacity for adsorption of methylene blue (195.31mg/g). Based on their excellent photocatalysis and adsorption properties, TiNTs-120-2 could simultaneously remove methyl orange, methylene blue, Pb2+, and phenol initially present in a compound pollution system, and the materials could be efficiently reused after a simple further treatment. In addition, TiNT-120-2 is well suited to sedimentation, and so has strong potential for application as an easily separable and recoverable material.
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      PubDate: 2013-12-31T01:08:58Z
       
  • N2 in ZIF-8: Sorbate induced structural changes and self-diffusion
    • Abstract: Publication date: 15 March 2014
      Source:Microporous and Mesoporous Materials, Volume 187
      Author(s): T. Chokbunpiam , R. Chanajaree , T. Remsungnen , O. Saengsawang , S. Fritzsche , C. Chmelik , J. Caro , W. Janke , S. Hannongbua
      In the field of nanoporous materials, guest-induced structural changes in metal–organic frameworks (MOFs) attracted great attention over the last years. One example concerns a gate-opening effect in MOF ZIF-8 which was found to occur upon sorption of N2. To mirror these structural changes in molecular simulations, suitable force fields for the proper description of framework flexibility are required. We demonstrate that our previously published force field is able to reproduce these structural changes in classical MD simulations. In particular, with our parameter set the diameter of the windows connecting adjacent cavities is found to match the X-ray values almost perfectly. We focus on investigating the impact of the structural changes on the mobility of N2 molecules in ZIF-8 framework and compare the results with those of another parameter set, which was published recently by Zhang and coworkers. The size of the windows increases notably, when the critical “gate-opening” loading is surpassed. Most surprisingly, this pronounced increase does not result in a speed-up of the N2 self-diffusivity. It appears, that a complex interplay of host-host and host-guest interactions increases the mutual hindrance of the N2 molecules and counter balance the acceleration of the mobility due to the larger window size.
      Graphical abstract image Highlights

      PubDate: 2013-12-31T01:08:58Z
       
  • A hard-templating route towards ordered mesoporous tungsten carbide and
           carbide-derived carbons
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Lars Borchardt , Martin Oschatz , Sven Graetz , Martin R. Lohe , Mark H. Rümmeli , Stefan Kaskel
      Ordered mesoporous tungsten carbide materials are synthesized via a nanocasting approach starting from hexagonal (SBA-15) and cubic (KIT-6) ordered silica templates. A tungsten chloride/sucrose precursor is converted into the desired ceramic by a thermal treatment in hydrogen and argon within the pores of the templates. The resulting materials show high BET surface areas and specific pore volumes of 431m2/g and 0.53cm3/g, respectively. They can be further converted to carbide-derived carbons (CDC) by metal atom extraction using hot chlorine gas. The ordered structure of the carbide matrix can be fully retained and the BET surface area and pore volume are noticeably enhanced to high values of 1246m2/g and 1.63cm3/g, respectively.
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      PubDate: 2013-12-31T01:08:58Z
       
  • Synthesis of lacunary polyoxometalate encapsulated into hexagonal
           mesoporous silica and their catalytic performance in esterification
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Naijin Wu , Baoshan Li , Wei Ma , Chunying Han
      The lacunary polyoxometalate (LPOM) encapsulated into the hexagonal mesoporous silica matrix materials were successfully prepared via a directly synthesis method by adjusting pH of the preparation system from 2.0 to 6.0. The materials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, N2 adsorption–desorption measurements, scanning electron microscopy, X-ray fluorescence analysis, and high-resolution transmission electron microscopy. The results show that the samples possess an ordered pore structure with which changed from uniform ribbing-type to cobweb shape cavity along with the LPOM content increasing from 0% to 30%. The materials possess a high specific surface area of 878–626m2 g−1 and a mesopore diameter of about 3.8nm. They also show an excellent catalytic performance and a good reusability for the esterification of n-butanol with acetic acid.
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      PubDate: 2013-12-31T01:08:58Z
       
  • Direct synthesis, characterization and catalytic application of SBA-15
           mesoporous silica with heteropolyacid incorporated into their framework
    • Abstract: Publication date: 15 March 2014
      Source:Microporous and Mesoporous Materials, Volume 187
      Author(s): Xiaoli Sheng , Jie Kong , Yuming Zhou , Yiwei Zhang , Zewu Zhang , Shijian Zhou
      The Keggin phosphotungstic acid, H3PW12O40 (HPW) incorporated into SBA-15 ordered mesoporous silica were synthesized via a method involving the introduction of HPW in an acidified solution of P123 triblock copolymer (EO20PO70EO20), the SBA-15 mesostructuring agent (direct synthesis). Samples with similar HPW loadings were also prepared by impregnation of SBA-15. A comparison between direct incorporation of HPW into mesoporous silica and impregnation of HPW on mesoporous silica was done. Characterization by elemental analysis, XRD, N2 adsorption, TEM, DRS-UV and FTIR spectroscopy showed that after calcination HPW in the direct synthesized samples was better dispersed or may even be partially embedded in the pore walls. Moreover, their catalytic behaviors were investigated in the alkylation of o-xylene with styrene. Results show that direct synthesized sample has the better catalytic performances in terms of yield and stability. This behavior may be owing to high dispersion of the HPW species on the SBA-15 and the strong interaction between the HPW and the support, thus prevent HPW leaching from the support.
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      PubDate: 2013-12-31T01:08:58Z
       
  • Solvothermal synthesis of disordered mesoporous materials based on a
           Si–N framework in ionic liquids
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): A.I. Saugar , A. Mayoral , J. Pérez-Pariente
      Silicon–nitrogen network based porous materials have been synthesized by a novel method based on the preparation of silicon diimide gel by the ammonolysis of silicon tetrachloride using an ionic liquid as solvent followed by a heating process. The resulting materials contain ionic liquid molecules occluded inside the framework, which can be remove by heat treatment at 600°C under flowing ammonia leading to microporous and mesoporous materials with high surface areas. The pore size of the materials is tailored by the variation of the experimental conditions. STEM investigations reveal a disordered porous structure with pores with an average diameter of 10nm in the mesoporous samples. A N/Si molar ratio higher than 2 is obtained for all the ammonia-calcined materials and FTIR and XPS measurements indicate a high number of Si–NH groups, both in the bulk and on the materials surface.
      Graphical abstract image Highlights

      PubDate: 2013-12-27T00:48:31Z
       
  • Highly enhanced selectivity for the separation of CH4 over N2 on two
           ultra-microporous frameworks with multiple coordination modes
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Xinyu Ren , Tianjun Sun , Jiangliang Hu , Shudong Wang
      Two typical ultra-microporous adsorbents namely [Ni3(HCOO)6] and [Co3(HCOO)6] were successfully prepared in a feasible route to scale up using non-corrosive methyl methanoate instead of formic acid. Pure gas and binary gas mixture adsorption equilibria of CH4 and N2 were conducted on the two compounds to evaluate their CH4 adsorption capacities and selectivities against N2. The two compounds exhibit preferential adsorption of CH4 over N2 at 298K in the pressure range 0.1–1.0MPa, and the adsorption selectivities of CH4/N2 mixture are determined to be 6.0–6.5 for [Ni3(HCOO)6] and 5.1–5.8 for [Co3(HCOO)6], respectively. The uniform ultra-micropores and optimal polarizability resulted from multiple coordination modes play the essential roles in their preferential adsorption of CH4 with the highest selectivities up to date, making the two compounds as promising candidates of existing adsorbents for unconventional natural gas upgrading.
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      PubDate: 2013-12-23T00:38:09Z
       
  • Ferrocene in the metal–organic framework MOF-5 studied by homo- and
           heteronuclear correlation NMR and MD simulation
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): M. Wehring , P.C.M.M. Magusin , S. Amirjalayer , R. Schmid , F. Stallmach
      Advanced solid-state 2D NMR spectroscopy and molecular dynamics computation are employed to investigate the interaction between adsorbed ferrocene molecules and the MOF-5 lattice. Relayed 13C–1H heteronuclear correlation (HETCOR) 2D NMR spectra clearly indicate short-distance contacts between the ferrocene guests and the benzene-1,4-dicarboxylic-acid linkers, mediated via intermolecular 1 H spin diffusion. By use of 2D 1H–1H correlation spectroscopy the distances between 1H nuclei in the guests and the linkers are estimated to be shorter than 0.5nm. MD computer simulations support the interpretation of the 2D solid state NMR studies. Moreover, they suggest a wide distribution of intermolecular distances in this host–guest system with the shortest intermolecular hydrogen–hydrogen distances of 0.15nm.
      Graphical abstract image

      PubDate: 2013-12-23T00:38:09Z
       
  • Breaking through tradeoff of Polysulfone ultrafiltration membranes by
           zeolite 4A
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Fu Liu , Bi-Rong Ma , Dong Zhou , Yan-hui Xiang , Li-xin Xue
      Pressure-driven ultrafiltration by porous membrane often encountered a tradeoff between permeability and selectivity due to the transport mechanism based on pore dimension. This paper aims to break through the tradeoff of Polysulfone (PSf) ultrafiltration membranes by incorporating specific zeolite 4A. The influences of particle size, micro-channel dimension, zeta potential and content of zeolite 4A on tradeoff were discussed. The morphological evolution investigated by Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) showed that zeolites 4A embedded in the selective layer within the depth of less than 1μm increased the surface roughness and improved the hydrophilicity. Thermal and mechanical stability were also evaluated by thermal gravimetric analysis (TGA) and tensile testing respectively. The filtration experiments showed that both pure water flux and rejection were simultaneously improved due to the morphology regulation, abundant nano-scale water flow channels, negatively charged membrane surfaces and precise embedding position of zeolite 4A in the membrane selective layer.
      Graphical abstract image

      PubDate: 2013-12-23T00:38:09Z
       
  • Acid property of MFI-type zeolites probed by trimethylphosphine oxide
           studied by solid-state NMR
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Shigenobu Hayashi , Keiko Jimura , Natsuko Kojima
      Acid properties of ZSM-5 type zeolite are studied by solid-state NMR using trimethylphosphine oxide (TMPO) as a probe molecule. TMPO is introduced from the gas phase at 373K. The amounts of the loaded TMPO are quantified by the signal intensities of 1H MAS NMR spectra, which are compared with the numbers of Brønsted acid sites estimated by the Si/A ratio of the framework derived from 29Si MAS NMR spectra and the content of fourfold-coordinated Al from 27Al MAS NMR spectra. The use of 373K for loading the probe molecules increases the loading level of TMPO, and thus almost all the acid sites are probed. The 31P chemical shifts in the range between 90 and 60ppm are attributed to TMPO adsorbed on Brønsted acid sites, whereas the signals between 60 and 40ppm are ascribed to TMPO adsorbed on other sites than Brønsted acid sites. The 13C chemical shift of methyl groups in the adsorbed TMPO depends mainly on the confined space as well as on the acid strength.
      Graphical abstract image

      PubDate: 2013-12-19T00:03:47Z
       
  • Organotemplate-free, seed-directed, and rapid synthesis of Al-rich zeolite
           MTT with improved catalytic performance in isomerization of m-xylene
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Qinming Wu , Xiong Wang , Xiangju Meng , Chengguang Yang , Yan Liu , Yinying Jin , Qi Yang , Feng-Shou Xiao
      m-xylene isomerization over zeolites is of great importance because of the shortage of p-xylene currently. Here, we show an organotemplate-free, seed-directed, and rapid synthesis of Al-rich zeolite MTT (denoted as ZJM-6) with improved catalytic performance in isomerization of m-xylene to p-xylene. Physicochemical characterizations including XRD, SEM, Ar sorption isotherms, 27Al NMR, and NH3-TPD show that the zeolitic product has good crystallinity, uniform crystals, high surface area, tetrahedral Al3+ species, and abundant acidic sites. Interestingly, the crystallization of ZJM-6 takes very short time (5h at 170°C), compared with conventional MTT zeolites (20h at 170°C). Very importantly, catalytic tests for m-xylene isomerization show that H-form of ZJM-6 zeolite exhibits superior performance, which could be potentially important for industrial applications of ZJM-6 zeolite as a candidate in the future.
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      PubDate: 2013-12-19T00:03:47Z
       
  • On existence of hydroxyl nests in acid dealuminated zeolite Y
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Eric Senderov , Istvan Halasz , David H. Olson
      The removal of Al with acid solution from a zeolite framework is customarily associated with formation of framework defects known as hydroxyl nests, but their existence has not been unambiguously confirmed thus far. TPD and FTIR techniques were used here to identify such hydroxyl nests in a 22% acid dealuminated zeolite Y by comparing it to its non-dealuminated parent counterpart. Both zeolites, parent and dealuminated, were analyzed in fully alkaline Cs, Na ion exchanged form. TPD analysis showed that hydroxyl nests cannot be present in samples calcined above 200°C. FTIR study did not find any evidence for the existence of such units even in hydrated samples which had never been subjected to modification at temperatures higher than 80°C.
      Graphical abstract image

      PubDate: 2013-12-19T00:03:47Z
       
  • Nanoporous SnO2 prepared by a photochemical strategy: Controlling of
           specific surface area and photocatalytic activity in degradation of dye
           pollutants
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Wei Chen , Fengqiang Sun , Zhimin Zhu , Zhilin Min , Weishan Li
      Nanoporous SnO2 fine particles with controlled specific surface area were prepared in the SnSO4 and H2SO4 mixed solutions by a simple photochemical method for the first time. Compared with other solution methods, the controlling of surface area can be manipulated at room temperature without the addition of any surfactant or template. Only by controlling the concentration of H2SO4, the specific surface area of the product could be tuned in the range of 13–203m2 g−1. They showed high activity and can be applied to efficient photocatalytic degradation of dye pollutants under a low power (8W 254nm) UV lamp. It was found the activity gradually increased with the increase of the specific surface area or the increase of the concentration of H2SO4 employed in the preparation process. The formation of SnO2 and pore structures, the morphologies, the compositions and the photocatalytic degradation mechanisms were systematically studied.
      Graphical abstract image

      PubDate: 2013-12-19T00:03:47Z
       
  • Effects of dealumination and desilication of H-ZSM-5 on xylose dehydration
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Su Jin You , Eun Duck Park
      The continuous liquid-phase dehydration of d-xylose into furfural was examined over various zeolites (H-ferrierite, H-ZSM-5, H-mordenite, H-β, and H-Y) having a similar surface area, external surface area, and amount of acid sites to determine the effects of zeolite structure on catalytic performance. Xylose conversion was proportional to the zeolite channel size, whereas the H-ZSM-5 zeolite showed the highest furfural selectivity due to shape-selectivity. In order to improve the catalytic activity, H-ZSM-5 zeolite was dealuminated or desilicated using an aqueous solution of HCl or NaOH, respectively. The prepared catalysts were characterized using N2 physisorption, X-ray diffraction (XRD), solid-state 27Al and 29Si magic-angle spinning nuclear magnetic resonance (MAS/NMR) spectroscopy, temperature-programmed desorption of ammonia (NH3-TPD) and isopropylamine (IPA-TPD). Dealumination of H-ZSM-5 appeared to remove extra-framework Al species without a collapse of the crystalline zeolite framework, while desilication generated extra-framework Al species accompanied by destruction of the zeolite framework. Among the tested catalysts, dealuminated H-ZSM-5 showed the highest furfural selectivity.
      Graphical abstract image

      PubDate: 2013-12-19T00:03:47Z
       
  • CO2 adsorption by amine modified siliceous mesostructured cellular foam
           (MCF) in humidified gas
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Dirgarini J.N. Subagyono , Marc Marshall , Gregory P. Knowles , Alan L. Chaffee
      A set of branched and linear polyethyleneimine (PEI) modified mesocellular siliceous foams (MCF) were evaluated as adsorbents for CO2 capture at modestly elevated temperatures under conditions that simulate the vacuum swing adsorption (VSA) process in humidified gas. Increasing the temperature was found to be beneficial for achieving reversible CO2 adsorption/desorption with reasonable capacities and rates. Under humid conditions, the materials lost 0–15% of their adsorption capacities in 0.5atm CO2 compared to under dry conditions at 105–115°C. The working capacity (0.025–0.15atm CO2) at 105°C was 2–17% higher under humid than under dry conditions. During cycling, the branched PEI adsorbent showed a gradual decrease in CO2 adsorption–desorption capacity under dry conditions, but the reduction in capacity was significantly reduced under wet conditions. The reduction in CO2 adsorption capacity was attributed to by-product formation, confirmed by IR, 13C CP-MAS NMR and EDS. In a humid environment, the formation of by-product was significantly reduced.
      Graphical abstract image

      PubDate: 2013-12-19T00:03:47Z
       
  • Thin oriented AFI zeolite membranes for molecular sieving separation
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Chao Ji , Ye Tian , Yongdan Li , Y.S. Lin
      Oriented AFI zeolite membranes are difficult to prepare in spite of their many potential applications. This paper reports reproducible synthesis of c-oriented, thin SAPO-5 zeolite membrane on macroporous ceramic support by a seeded-secondary growth method. A c-oriented SAPO-5 crystal monolayer was deposited on a macroporous alumina support precoated with a polyvinyl alcohol film. The c-oriented SAPO-5 seed layer was deposited by spray-blowing of powder of well-defined hexagonal SAPO-5 crystal plates of about 1μm in side length and 200nm in thickness. The SAPO-5 seed layer on the alumina support was then gown to a continuous, 1.5μm thick, c-oriented SAPO-5 membrane in a secondary growth step. The SAPO-5 membranes prepared in this work show molecule-sieving separation characteristics for hydrocarbons with molecular size close to the intracrystalline pore size of SAPO-5. The synthesis method reported in this work is simple and quite reproducible, and it produces c-oriented SAPO-5 membranes with higher organic permeability and permeance, and better separation characteristics than other methods reported in the literature.
      Graphical abstract image

      PubDate: 2013-12-19T00:03:47Z
       
  • In situ synthesis of a drug-loaded MOF at room temperature
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Negar Motakef-Kazemi , Seyed Abbas Shojaosadati , Ali Morsali
      In the present study, in situ synthesis of a drug-loaded metal–organic framework (MOF) was accomplished at room temperature. The produced drug-loaded MOF [{Zn2(1,4-bdc)2(dabco)}n] was then studied as a drug delivery system and exhibited the ability to entrap ibuprofen model drug. The ibuprofen loading efficiency of the MOF was 15% (w/w) in the selected synthesis conditions. The drug release was also monitored and 80% of the loaded drug was released over 12days. The MOF was characterized by IR spectroscopy, X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), UV–vis spectroscopy, N2 adsorption porosimetric (BET), and field emission scanning electron microscopy (FE-SEM). The IC50 value, cytotoxicity, of Zn2(1,4-bdc)2(dabco) for human Hepatoma cell (HuH7) was determined to be 1mg/ml by MTT assay.
      Graphical abstract image

      PubDate: 2013-12-14T23:29:35Z
       
  • EPR and UV–vis study on solutions of Cu(II) dmit complexes and the
           complexes entrapped in zeolite A and ZIF-Cu(IM)2
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): S.K. Hoffmann , J. Goslar , S. Lijewski , K. Tadyszak , A. Zalewska , A. Jankowska , P. Florczak , S. Kowalak
      The 1,3-dithiole-2-thione-4,5-dithiolate (C3S5 2– ≡ dmit) complexes with Cu(II) in solutions and deposited into zeolite NaA and into metal–organic framework (MOF) with zeolitic imidazole structure ZIF-Cu(IM)2B were studied by UV–vis and EPR spectroscopy. UV–vis spectra show that intermolecular π–π∗ transitions existing in the visible region can be used for an identification of the molecules deposited in solid matrices. EPR of Cu(dmit)2 complexes in frozen (77K) DMF (dimethylformamide) solution indicates tetrahedral CuS4 coordination with compressed structure of D2d symmetry and EPR parameters g =2.089, g ⊥ =2.0257, A =145.4×10−4 and A ⊥ =29.8×10−4 cm−1. We were looking for such complexes after impregnation of the zeolites NaA with dmit solutions. We found that the Cu(dmit)2 complex in zeolite NaA appears together with Cu(II) complexes being coordinated by host oxygen atoms. The Cu(dmit)2 complexes are, however, deformed to the elongated D2d symmetry. In ZIF-Cu(IM)2B the slightly more axially compressed tetrahedral Cu(dmit)2 complexes appear as a result of coordination of the host Cu(II) ions with captured dmit molecules. The host structure is preserved, exchange coupling between host Cu(imidazole)4 complexes is strongly weakened and separated Cu-imidazole and Cu(dmit)2 complexes can be distinguished.
      Graphical abstract image

      PubDate: 2013-12-14T23:29:35Z
       
  • Mesoporous bioactive glass and glass–ceramics: Influence of the
           local structure on in vitro bioactivity
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Chitra Vaid , Sevi Murugavel , Chandasree Das , Sundarrajan Asokan
      Mesoporous quaternary bioactive glasses and glass–ceramic with alkali–alkaline-earth oxide were successfully synthesized by using non-ionic block copolymer P123 and evaporation induced self assembly (EISA) process followed by acid treatment assisted sol–gel method. As prepared samples has been characterized for the structural, morphological and textural properties with the various analytical techniques. Glass dissolution/ion release rate in simulated body fluid (SBF) was monitored by inductively coupled plasma (ICP) emission spectroscopy, whereas the formation of apatite phase and its crystallization at the glass and glass–ceramic surface was examined by structural, textural and microscopic probes. The influence of alkaline-earth oxide content on the glass structure followed by textural property has become more evident. The pristine glass samples exhibit a wormhole-like mesoporous structure, whereas the glass–ceramic composition is found to be in three different phases, namely crystalline hydroxyapatite, wollastonite and a residual glassy phase as observed in Cerabone® A/W. The existence of calcium orthophosphate phase is closely associated with the pore walls comprising nanometric-sized “inclusions”. The observed high surface area in conjunction with the structural features provides the possible explanation for experimentally observed enhanced bioactivity through the easy access of ions to the fluid. On the other hand, presence of multiple phases in glass–ceramic sample inhibits or delays the kinetics of apatite formation.
      Graphical abstract image Highlights

      PubDate: 2013-12-14T23:29:35Z
       
  • Seed-directed, rapid synthesis of MAZ-type zeolites without using organic
           structure-directing agent
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Akari Ogawa , Kenta Iyoki , Yoshihiro Kamimura , Shanmugam Palani Elangovan , Keiji Itabashi , Tatsuya Okubo
      MAZ-type zeolites (omega) were successfully obtained for the first time using a seed-directed, organic structure-directing agent-free synthesis method according to the “Composite Building Unit Hypothesis” surprisingly in a short period (ca. 30h) of hydrothermal treatment. The obtained product showed textural and acidic properties that were superior to the omega seed crystals synthesized using tetramethylammonium hydroxide as an organic structure-directing agent. Therefore, we believe the new technique is an efficient and environmentally friendly process for the preparation of MAZ-type zeolites for their use as adsorbents, catalysts, and so on. In addition, the “Composite Building Unit Hypothesis” was confirmed to be applicable for the synthesis of 4R-rich zeolites in the (Na, K)-aluminosilicate system.
      Graphical abstract image

      PubDate: 2013-12-14T23:29:35Z
       
  • Corrigendum to “Supercapacitive property of
           metal–organic-frameworks with different pore dimensions and
           morphology” [Micropor. Mesopor. Mater. 171 (1) (2013) 53–57]
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Deok Yeon Lee , Dipak V. Shinde , Eun-Kyung Kim , Wonjoo Lee , In-Whan Oh , Nabeen K. Shrestha , Joong Kee Lee , Sung-Hwan Han



      PubDate: 2013-12-14T23:29:35Z
       
  • Interaction of CO probe molecules with Cu(+) in MCM-22 zeolite
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Karel Frolich , Roman Bulánek , Eva Frýdová
      The interaction of CO probe with copper exchanged MCM-22 zeolite is studied. Particularly, the heterogeneity of Cu(+) ions is examined. For this purpose, combined CO adsorption microcalorimetry with FTIR of CO adsorption/desorption at RT and elevated temperature is originally exploited. Contribution brings the first experimental evidence for three families of Cu(+) ions differing in the interaction energy with CO and exhibiting Q diff around 107, 100–97 and ⩽92kJmol−1, respectively. The energy distribution determined from calorimetry and desorption curves is due to copper coordination differences. Despite wide energetic distribution of carbonyls, only two bands in IR spectra at 2159 and 2150cm−1 are observed. Similarly to other zeolites, Cu(+) loses its original coordination to framework during the CO adsorption. The preferred trigonal planar geometry with CO and two zeolite oxygen gives rise to the band at 2159cm−1. Peculiarly for MCM-22, significant amount of Cu(+) ions stay three-coordinated to the zeolite after CO adsorption, relate to mediate interaction energies and correspond to the band at 2150cm−1. Characteristic changes on the IR spectrum revealed that the enhanced movement of ions after CO exposure occurs at higher temperature. The influence of zeolite composition, namely Cu loading and Si/Al ratio, on the character of IR spectrum and population of energetic components is discussed.
      Graphical abstract image

      PubDate: 2013-12-14T23:29:35Z
       
  • Supercapacitors based on freeze dried MnO2 embedded PEDOT: PSS hybrid
           sponges
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): R. Ranjusha , K.M. Sajesh , S. Roshny , V. Lakshmi , P. Anjali , T.S. Sonia , A. Sreekumaran Nair , K.R.V. Subramanian , Shantikumar V. Nair , K.P. Chennazhi , A. Balakrishnan
      The present study investigates in detail the synthesis and characterization of PEDOT: PSS/MnO2 hybrid sponge electrodes for supercapacitor/battery applications. These hybrid sponges were prepared using freeze drying technique and showed hierarchical pores ranging from micron to nanometric size. Scanning electron microscopy-energy dispersive X-ray showed uniform dispersion of MnO2 along the PEDOT: PSS matrix. Thermo gravimetric-differential thermal analysis showed higher thermal stability for these hybrid constructs compared to PEDOT: PSS sponges. From the electrochemical studies, an intrinsic correlation between overall specific capacitance, morphology and weight percentage of MnO2 in the PEDOT: PSS matrix has been defined and explained in KOH electrolyte system. High cyclic stability was observed at the end of 2000 cycles for these hybrid sponges with less than 5 % capacitance fading. These sponges exhibit mass specific capacitance values as high as 10688Fg−1 which was found to be 35% higher compare to PEDOT: PSS sponges as obtained from Weibull statistics. The application of these electrodes was explored in a fully functional asymmetric coin cell unit where an energy and power density of 200mWhkg−1 and 6.4kWkg−1, was obtained, respectively.
      Graphical abstract image

      PubDate: 2013-12-14T23:29:35Z
       
  • Preparation of magnetic core/shell structured γ-Fe2O3@Ti-tmSiO2 and
           its application for the adsorption and degradation of dyes
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Qiang Lv , Gang Li , Hongying Sun , Linghao Kong , Hong Lu , Xiaoxia Gao
      A core/shell structured γ-Fe2O3@Ti-tmSiO2 nanocomposite with enhanced activity for the degradation of dyes that is capable of fast magnetic separation has been successfully prepared by a sol–gel process followed with calcination. The obtained core/shell structure is composed of a superparamagnetic core with a strong response to external fields, and an outer layer of porous titanium silicate with a tunable porous sizes. The convenient control over the pore size and the thickness of porous silica containing titanium species may make it possible to adsorb and catalyze molecules with different sizes. The presence of porous SiO2 helps to enhance the chemical and thermal stability of γ-Fe2O3 core. It is demonstrated that the core γ-Fe2O3 as a Fenton-like catalyst exhibits good performance, while the Ti4+ existing in the porous shell also gives obvious activity in the degradation of dyes. The composite γ-Fe2O3@Ti-tmSiO2 possesses enhanced activity for the treatment of pollutants in water.
      Graphical abstract image Highlights

      PubDate: 2013-12-10T22:48:54Z
       
  • Prehydrolysis approach to direct synthesis of Fe, Al, Cr-incorporated
           SBA-15 with good hydrothermal stability and enhanced acidity
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Bo Sun , Lei Li , Zhaoyang Fei , Shusheng Gu , Ping Lu , Weijie Ji
      The Fe-incorporated mesoporous SBA-15 materials with the Fe content up to a Fe/Si molar ratio=0.05 were synthesised via pre-hydrolysis of tetraethyl orthosilicate (TEOS) employing P123 triblock copolymer as the template. The synthetic strategy is the hydrolysis of Fe salt precursor can provide acidic medium essential for the pre-hydrolysis of TEOS. Different Fe/Si ratios and TEOS pre-hydrolysis periods were employed to modify the structure and texture of the Fe-incorporated SBA-15. The impact of Fe sources (ferric nitrate, ferric chloride, and ferric sulfate) on the characteristics of Fe-SBA-15 has also been investigated. Ferric nitrate showed the best effect among the three Fe sources. UV–Vis study reveals that besides the four-coordinated iron species, the iron oxide domains may also exist in the samples. Pyridine adsorption IR study demonstrates enhancement in Brønsted and Lewis acidity of as-synthesised Fe-SBA-15 materials, potential as solid acid catalyst or catalyst support. Moreover, the employed treatments (700°C for 10h in air and 600°C for 3h in 100% steam) verified good thermal and hydrothermal stability of the derived Fe-SBA-15. For comparison, Al- and Cr-incorporated SBA-15, with the Al/Si and Cr/Si molar ratio of 0.08 and 0.05 respectively, were also synthesised through the same strategy.
      Graphical abstract image

      PubDate: 2013-12-10T22:48:54Z
       
  • Synthesis of aluminum-doped mesoporous zirconia with improved thermal
           stability
    • Abstract: Publication date: 1 March 2014
      Source:Microporous and Mesoporous Materials, Volume 186
      Author(s): Ruiping Liu , Chang-an Wang
      Mesoporous zirconia doped with varying amounts of aluminum are synthesized by the evaporation induced self-assembly (EISA) method, and their structure and textural properties are investigated extensively. The results show that in contrast to most other zirconia binary system, doping of zirconia with aluminum stabilizes tetragonal zirconia over the cubic phase, and the crystallization temperature of the as-obtained powders increases with increasing aluminum content, thereby improve the thermal stability of the mesoporous zirconia. The BET surface area and pore volume of the samples doped with the same amount of aluminum decreases with increasing calcination temperature, accompanied by an increase in the mean BJH pore size. Furthermore, the BET surface area and pore volume of the samples calcined at the same temperature increase with increasing amounts of aluminum. For sample with an Al/Zr molar ratio of 1, the disordered “wormhole-like” mesoporous structure remained even after calcination at 1000°C for 1h.
      Graphical abstract image

      PubDate: 2013-12-06T21:58:53Z
       
 
 
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