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Microporous and Mesoporous Materials

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ISSN (Print) 1387-1811
Published by Elsevier

[2564 journals]

FTIR study of N2 and CO adsorption on H-D-FER
- Abstract: Publication date: 1 September 2013
  Source:Microporous and Mesoporous Materials, Volume 177
  Author(s): K. Chakarova , K. Hadjiivanov
  Low temperature adsorption of N2 on an H-D-FER sample was studied by FTIR spectroscopy in order to obtain information on the acidity of the hydroxyl groups. Three kinds of zeolite bridging hydroxyls were clearly distinguished, at 3609, 3596 and 3555cm−1 (3614, 3600 and 3556cm−1 at 100K). The respective OD groups were observed at 2662, 2653 and 2623cm−1 (2666, 2656 and 2621cm−1 at 100K). Nitrogen affects first the highest-frequency hydroxyls and last, the lowest frequency ones. A shift of the OH modes between 90 and 111cm−1 was measured for the different hydroxyls (between 64 and 79cm−1 for the OD groups). Experiments on CO adsorption have shown that this molecule was not convenient for measuring the acidity of the bridging hydroxyls because the spectra are complicated as a result of Fermi resonance and solvatation effects.
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  PubDate: 2013-05-19T05:32:01Z
Hydrogen adsorption properties of platinum decorated hierarchically structured templated carbons
- Abstract: Publication date: 1 September 2013
  Source:Microporous and Mesoporous Materials, Volume 177
  Author(s): Hyunchul Oh , Thomas Gennett , Plamen Atanassov , Mert Kurttepeli , Sara Bals , Katherine E. Hurst , Michael Hirscher
  In this report, the possibility of Pt catalytic activity for the dissociation of hydrogen molecules and subsequent hydrogen adsorption on sucrose templated carbon at ambient temperature has been studied. In order to investigate Pt catalytic effect for hydrogen storage solely, 6.8wt.% Pt-doped (Pt/TC) and pure templated carbon (TC) possessing almost identical specific surface area (SSA) and pore volume (Vp) have been successfully synthesized. Since both Pt/TC and TC shares for their textural properties (e.g. SSA and Vp), any difference of hydrogen adsorption characteristic and storage capacity can be ascribed to the presence of Pt nanoparticles. Both samples are characterized by various techniques such as powder X-ray diffraction, ICP-OES, Raman spectroscopy, transmission electron microscopy, cryogenic thermal desorption spectroscopy, low-pressure high-resolution hydrogen and nitrogen BET and high-pressure hydrogen adsorption isotherms in a Sieverts’ apparatus. By applying hydrogen and deuterium isotope mixture, cryogenic thermal desorption spectroscopy point to a Pt catalytic activity for the dissociation of hydrogen molecules. Furthermore, the hydrogen adsorption isotherms at RT indicate an enhancement of the initial hydrogen adsorption kinetics in Pt-doped system. However, the hydrogen storage capacity of Pt/TC exhibits a negligible enhancement with a strong hysteresis, suggesting no connection between the spillover effect and a feasible hydrogen storage enhancement.
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  PubDate: 2013-05-19T05:32:01Z
In vitro release of l-phenylalanine from ordered mesoporous materials
- Abstract: Publication date: 1 September 2013
  Source:Microporous and Mesoporous Materials, Volume 177
  Author(s): Joanna Goscianska , Anna Olejnik , Robert Pietrzak
  The applicability of different types of mesoporous materials as pharmaceutical carriers for l-phenylalanine was evaluated. Silicas, such as SBA-15, SBA-16 and KIT-6 were synthesised by hydrothermal method with tetraethyl orthosilicate as the silica source and triblock copolymer P123 as a template. XRD and TEM studies confirmed an ordered hexagonal structure of SBA-15 and a cubic structure of SBA-16 and KIT-6. The materials are characterised by well-developed specific surface areas and large pore volumes. Adsorption of l-phenylalanine over various mesoporous silicas was studied from solution of different pH (5.6–9.4). The greatest sorption capacity was observed at pH 5.6, which is close to the isoelectric point of l-phenylalanine (pI=5.48). The amount of l-phenylalanine adsorbed on the mesoporous materials decreases at pH 5.6 in the following sequen KIT-6>SBA-15>SBA-16 that was strongly related to the average pore diameter of the samples. The structural and textural features of the silicas seem to be responsible for the different l-phenylalanine release rate. Additionally, it was found that L-Phe release rate exhibited the pH sensitivity. These phenomena allow control of the experiment according to the needs.
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  PubDate: 2013-05-15T08:02:29Z
Adsorption of 2,3-DCDD on FAU and EMT-type zeolites: Influence of the nature and the content of charge compensating cations
- Abstract: Publication date: 1 September 2013
  Source:Microporous and Mesoporous Materials, Volume 177
  Author(s): Maud Mercury , Nabila Zouaoui , Angélique Simon-Masseron , Yves Zerega , Christelle Reynard-Carette , Renaud Denoyel , Michel Carette , Michel Soulard , Aurika Janulyte , Joël Patarin
  The nature and the content of exchangeable cations in FAU and EMT-type zeolites on the adsorption of dioxin are investigated. These zeolites are selected due to their pore openings, close to the diameter of the 2,3-dichlorodibenzo-p-dioxin (0.74nm). In this study, the sodium cations, which balance the negative charge of the zeolitic framework, are replaced by other cationic species such as H+, Mg2+, Li+, Ca2+, K+ and Ag+. The structural and textural analyses performed on the exchanged zeolites indicate that the exchange reaches 70–98% and the structure of zeolites is preserved during the exchange process. For both zeolite structure types, the dioxin adsorption rates are the highest for the sodium forms followed by the calcium forms. The following order is obtained: Na+ >Ca2+ =Li+ >Mg2+ =Ag+ >K+. It is also noticed that for a same type of zeolite (FAU), the adsorption rate is inversely proportional to the framework Si/Al molar ratio which is related to the content of sodium cations.
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  PubDate: 2013-05-15T08:02:29Z
Synthesis of highly loaded and well dispersed CuO/SBA-15 via an ultrasonic post-grafting method and its application as a catalyst for the direct hydroxylation of benzene to phenol
- Abstract: Publication date: 1 September 2013
  Source:Microporous and Mesoporous Materials, Volume 177
  Author(s): Xiaowei Zhang , Ni Huang , Ge Wang , Wenjun Dong , Mu Yang , Yi Luan , Zhan Shi
  A novel ultrasonic post-grafting method has been developed to obtain highly-loaded and well-dispersed CuO nanoclusters inside the channels of mesoporous silica (SBA-15). Trimethylchlorosilane (TMCS) and 3-aminopropyltriethoxysilane (APTES) were used as modification surfactants, and copper nitrate solution was used as the precursor. The samples were characterized by FT-IR, XRD, SAXRD, ICP-AES, BET, HRTEM, TPR and XPS, which illustrated that the CuO clusters were well-dispersed in very small sizes. The hydroxylation of benzene to phenol in a one-step liquid-phase process using CuO/SBA-15 as the catalyst was evaluated. High conversion (28%) and selectivity (95%) were achieved with a 13.4wt.% copper grafted on SBA-15. Furthermore, the catalyst was shown to have the ability to be recycled up to five times without a significant loss of conversion or selectivity.
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  PubDate: 2013-05-15T08:02:29Z
Carbon dioxide storage and sustained delivery by Cu2(pzdc)2L [L=dipyridyl-based ligand] pillared-layer porous coordination networks
- Abstract: Publication date: 1 September 2013
  Source:Microporous and Mesoporous Materials, Volume 177
  Author(s): Omar J. García-Ricard , Paul Meza-Morales , Juan C. Silva-Martínez , Maria C. Curet-Arana , John A. Hogan , Arturo J. Hernández-Maldonado
  CPL-2 (Cu2(pzdc)2(bpy)), CPL-5 ((Cu2(pzdc)2(bpe)), and ZIF-8 (Zn(MeIM)2) [pzdc =2,3-pyrazinedicarboxylate, bpy =4,4′bipyridine, bpe =1,2-di-(4-pyridyl)-ethylene, MeIM=2-methylimidazolate] were used to study carbon dioxide storage and delivery at low to moderate pressures. Both CPL-2 and CPL-5 showed superior performance over ZIF-8 due to better volumetric-based capacities and superior diffusion kinetics exhibited by the former metal organic frameworks. When compared with an empty vessel, the CPL-n based storage/delivery system provided as much as 500% increase in CO2 constant flow supply time at moderate pressures. A simplified phenomenological yet useful model was developed to predict discharge pressure decay and estimate a lumped parameter related to the molecular diffusivity. Density functional theory was also employed to shed light onto the CO2 hysteretic adsorption process present on the CPL-n materials. Greater CO2 binding interactions were observed near the vicinity of the copper-nodes.
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  PubDate: 2013-05-15T08:02:29Z
Facile structure-controlled synthesis of mesoporous γ-alumina: Effects of alcohols in precursor formation and calcination
- Abstract: Publication date: 1 September 2013
  Source:Microporous and Mesoporous Materials, Volume 177
  Author(s): Baiyu Huang , Calvin H. Bartholomew , Brian F. Woodfield
  We report a facile synthesis of mesoporous alumina catalysts supports with controlled pore properties by varying the alcohols used in the rinsing and gelation of boehmite/bayerite precursors derived from a controlled hydrolysis of aluminum alkoxides. X-ray diffraction, transmission electron microscopy, nitrogen gas adsorption, and comparative adsorption analysis were performed to determine the structure of these materials. After calcination at 700°C for 2h, surface areas of these synthesized alumina catalysts supports range from 180 to 260m2/g, average pore widths range from 7 to 37nm, and pore volumes range from 0.8 to 1.4cm3/g. Accordingly, this synthetic method provides a facile route to the controlled synthesis of nanostructured alumina catalyst supports with customized pore structures, including a wide range of mesopore widths.
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  PubDate: 2013-05-15T08:02:29Z
Intrinsic relationships between proton conductivity and nanopore size and functionalization
- Abstract: Publication date: 1 September 2013
  Source:Microporous and Mesoporous Materials, Volume 177
  Author(s): Marshall T. McDonnell , David J. Keffer
  A fundamental understanding of the relationship between the nanoscale structure of proton exchange membranes (PEMs) and their proton conductivity would be exceedingly useful in optimizing existing and designing new materials. In this work, a set of structural descriptors, accounting for nanopore size, functionalization and connectivity are employed to predict proton conductivities in PEMs. The model reproduces experimentally determined conductivities in two PEMs. The model is applied to water-filled cylindrical nanopores functionalized on their interior surface with acid groups. It is demonstrated that for cylindrical nanopores of a given radius there is an optimal surface coverage of acid groups. The optimum can be sharply peaked, indicating that non-optimal surface coverages (either too low or too high) drastically reduce the conductivity of the pore. The theoretical maximum conductivity through a cylindrical nanopore is calculated to be about 0.70S/cm at 300K.
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  PubDate: 2013-05-15T08:02:29Z
Modelling selective separation of trypsin and lysozyme using mesoporous silica
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): D. Baowan , N. Thamwattana
  The selective separation of biomolecules is a critical process in food, biomedical and pharmaceutical industries. Due to its size and properties, mesoporous silica offers many advantages as a separation media for biomolecules such as proteins and enzymes. In this paper, we investigate mathematically the separation of proteins trypsin and lysozyme using mesoporous silica materials. These proteins are modelled as densely packed spheres, while the silica pore is assumed to have a cylindrical structure. The Lennard–Jones potential together with a continuum approximation is employed to determine the interaction among the proteins and the interaction between a protein and a silica pore. For these systems, the total interaction energies are obtained analytically as functions of the protein size and the pore dimensions. We find that the pore radii which give rise to the maximum adsorption energies for trypsin and lysozyme are 21.74Å and 17.74Å, respectively. Since the binding energy between any two protein molecules is found to be three orders of magnitude lower than the adsorption energy of the protein into the silica pore, proteins prefer to be separated and stay inside the pore. Further, we find that using silica pores with radii in the range between 17.23Å and 21.24Å allows the entrance of only lysozyme, as such separating lysozyme from trypsin. These results agree with previous experimental study, confirming that mesoporous silica pores may be used to separate trypsin–lysozyme mixture.
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  PubDate: 2013-05-11T08:03:18Z
Editorial Board
- Abstract: Publication date: 15 July 2013
  Source:Microporous and Mesoporous Materials, Volume 175
  
  PubDate: 2013-05-11T08:03:18Z
Amorphous carbamazepine stabilization by the mesoporous silicate SBA-15
- Abstract: Publication date: 1 September 2013
  Source:Microporous and Mesoporous Materials, Volume 177
  Author(s): Valeria Ambrogi , Fabio Marmottini , Cinzia Pagano
  The poor solubility carbamazepine (CARBA) is the main responsible for its low and variable bioavailability. This problem is strictly connected to the high energy required for CARBA crystal lattice disruption that represents the rate determining step of the dissolution process. CARBA dissolution enhancement can be achieved by converting the crystals ordered structure in the amorphous solid state in which the molecules show a high mobility, requiring less energy for intermolecular bond breaking. Unfortunately CARBA amorphous form is unstable and turns into the crystalline one. The aim of this work was the improvement of CARBA dissolution by its conversion in the amorphous form and its stabilization by inclusion in the mesoporous silica material SBA-15. CARBA was loaded by a simple, safe and eco-friendly method obtaining a high final drug loading (40% wt.). The obtained inclusion product showed improved drug dissolution and good physical stability in comparison to crystalline CARBA. Interesting results were obtained also for the physical mixture of SBA-15 and CARBA which showed an increase of drug dissolution. Moisture effects on drug amorphous form stability are discussed as well.
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  PubDate: 2013-05-11T08:03:18Z
The high thermal stability of the synthetic zeolite K–L: Dehydration mechanism by in situ SR-XRPD experiments
- Abstract: Publication date: 1 September 2013
  Source:Microporous and Mesoporous Materials, Volume 177
  Author(s): Lara Gigli , Rossella Arletti , Simona Quartieri , Francesco Di Renzo , Giovanna Vezzalini
  Thermally induced structural modifications of a synthetic zeolite L [K8.46 (Al8.35 Si27.53) O72·17.91H2O, framework type LTL, s.g. P6/mmm, a =18.3367(1) and c =7.5176(1)Å] were studied by temperature-resolved synchrotron X-ray powder diffraction. In the investigated temperature range (RT-814°C), neither structure breakdown nor phase transitions occurred. The largest unit cell deformation was observed between 100° and 240°C, accompanied by an increase and decrease of the a and c cell parameters, respectively. After complete water release, an inversion of the a and c parameter behavior was observed, while the cell volume continued to increase, although following a more flattened curve. Overall, in the investigated T range, a small cell volume increase of 0.7% was observed. The release of the five water molecules present in zeolite L started with the most weakly bonded one and occurred between 80° and 240°C. During dehydration the framework underwent minor rearrangements, which facilitated water release: the apertures of the main 12-ring and the 8-ring channels became more circular and the 6-membered rings became more hexagonal. The thermal expansion of zeolite L, very unusual for a non-siliceous zeolite, was interpreted and compared with previous data reported in literature for this porous material, and with the behavior of the synthetic phases ITQ-4 and CIT-5.
  Graphical abstract Highlights • In-situ dehydration of zeolite L was studied between RT and 814°C. • The largest unit cell deformation was observed in correspondence of water release. • In the investigated T range, a small cell volume increase of 0.7% was observed. • Water release is facilitated by minor framework deformations. • The thermal expansion of zeolite L is very unusual for a non-siliceous zeolite.
  
  PubDate: 2013-05-11T08:03:18Z
Hardwood lignin pyrolysis in the presence of nano-oxide particles embedded onto natural clinoptilolite
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Nevenka Rajić , Nataša Zabukovec Logar , Aleksander Rečnik , Mohamad El-Roz , Frederic Thibault-Starzyk , Paul Sprenger , Lenka Hannevold , Anne Andersen , Michael Stöcker
  In this study the catalytic activity of Na-rich and MO-containing natural clinoptilolite (MO – nanoparticles of NiO, ZnO, or Cu2O) was studied in the pyrolysis of hardwood lignin. The clinoptilolite samples exhibit different catalytic activities which depend mainly on the type of the nano-oxide. The presence of nano-oxides did not affect the porosity of the clinoptilolite framework but influenced its acidity. However, it seems that acidity of the lattice did not influence the catalytic activity of the clinoptilolite in the pyrolisis of hardwood lignin. The number of Lewis acid sites increased significantly for the ZnO- and Cu2O-containing clinoptilolite whereas for the NiO-sample it did not change appreciably in comparison to the parent zeolite. The amount of phenols in the as-produced bio-oil varies from 39% for ZnO-clinoptilolite, 43% for Na-rich clinoptilolite, to 50 and 54% for Cu2O- and NiO-containing samples, respectively. The highest yield of phenols obtained in the presence of NiO-containing clinoptilolite is ascribed to a synergetic interaction of the clinoptilolite lattice and nano-NiO particles.
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  PubDate: 2013-05-07T03:20:43Z
Hydrothermal conversion of magadiite into mordenite in the presence of cyclohexylamine
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Zhifang Shi , Yu Wang , Changgong Meng , Xiaoyu Liu
  Hydrothermal conversion of magadiite, in the presence of cyclohexylamine (CHA), into a commercially important mordenite (MOR zeolite) has been investigated. The effects of various parameters such as the reactant H2O/SiO2 ratio, CHA/SiO2 ratio, reaction time, the presence of sodium ions and potassium ions are studied. Thermal and acid stability of the as-made MOR zeolite were examined. The pure MOR zeolite with high crystallinity, which is composed of parallelepiped crystals agglomerate, was obtained at 140°C for 28h with the molar composition: 0.14M2O:SiO2:xAl2O3:54H2O:16CHA (M2O=K2O+Na2O, K/K+Na=0.3, x =0.028 and 0.04). The structure of the sample was totally destroyed at 1100°C and the product is exceptionally stable towards strong acid.
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  PubDate: 2013-05-07T03:20:43Z
Synthesis of binderless zeolite aggregates (SOD, LTA, FAU) beads of 10, 70μm and 1mm by direct pseudomorphic transformation
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Maria Mańko , Jullian Vittenet , Jeremy Rodriguez , Didier Cot , Julie Mendret , Stephan Brosillon , Wacław Makowski , Anne Galarneau
  Pseudomorphic transformation is a promising alternative to conventional approaches for the preparation of binderless preshaped zeolite beads. However this method was until now restricted to zeolites synthesized in low alkaline media (OH−/SiO2 ≪1) (ZSM-5, FER, BEA), where the silica dissolution rate was slow in comparison to zeolite crystallization rate. In this study, we demonstrated the possibility to prepare binderless zeolite aggregates beads of SOD, LTA and FAU-X requiring usually high alkaline media (OH−/SiO2 >2). This was achieved by adding the right excess of aluminum to amorphous silica beads of the desired size and shape. Zeolite aggregate beads of SOD, LTA, FAU-X of 10, 70μm and 1mm were obtained in a one-step synthesis process with high synthesis yields. These zeolite beads are formed by an aggregation of small crystals of 1.5μm. The preservation of the adsorption properties of these zeolite pseudomorphs were highlighted by N2 sorption at −196°C and QE-TPDA of n-hexane experiments at room temperature. These zeolite beads would be highly suitable for column filling and continuous flow applications as catalysis or adsorption.
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  PubDate: 2013-05-07T03:20:43Z
Metal nanoparticles inside multi-walled carbon nanotubes: A simple method of preparation and of microscopic image analysis
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Xiaoming Wang , Nan Li , Lisa D. Pfefferle , Gary L. Haller
  A simple and efficient method was developed for the introduction of metal nanoparticles inside multi-walled carbon nanotubes (MWCNTs). The method is based on the incipient wetness impregnation using the aqueous solution of a metal salt precursor, followed by the reduction in hydrogen. A hydrophobic MWCNT outer surface is created, which minimizes the wetting of the impregnation solution on MWCNT outer surface, leading to the highly selective deposition of metal particles inside MWCNTs. The selectivity toward nanoparticles inside MWCNTs is about 80% based on a particle number average. Also, a new method was developed for the analysis of microscopic images from transmission electron microscope (TEM) so that the fraction of particles inside MWCNTs can be accurately characterized without 3D TEM. This method is based on the measurement of r/R , the ratio of the inside to outside diameters of the MWCNTs.
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  PubDate: 2013-05-07T03:20:43Z
Hierarchically porous silica as an efficient catalyst carrier for high performance vis-light assisted Fenton degradation
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Zehui Miao , Shengyang Tao , Yuchao Wang , Yongxian Yu , Changgong Meng , Yonglin An
  A kind of hierarchically porous silica (HPS) was used as an efficient catalyst carrier to load iron oxide small particles. The obtained Fe2O3/HPS hybrids were characterized by SEM, EDS, XRD, XPS, N2 adsorption–desorption isotherms, DFT and Hg porosimetry. The catalytic activity of the Fe2O3/HPS was evaluated by the degradation of azo-dye Orange II. The Fe2O3/HPS showed high catalytic activity to the photo-Fenton reaction with vis-light (λ >400nm) irradiation. More than 90% of dye in solution could be degraded. The effects of pH, H2O2 concentration, additive (hydroxylamine hydrochloride), leaching and stability tests were studied. The Fe2O3/HPS could work well in a wider pH range (2.5–8.5) than common homogeneous iron catalyst. Due to the excellent pore structure of HPS, Fe2O3/HPS exhibited much better catalytic ability than normal commercial hematite (Fe2O3) under the same experimental condition. Moreover, Fe2O3/HPS had an ideal stability for the degradation of Orange II after at least ten recycles.
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  PubDate: 2013-05-07T03:20:43Z
Selectivity of new siliceous zeolites for separation of methane and carbon dioxide by Monte Carlo simulation
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Mahmoud Rahmati , Hamid Modarress
  The adsorption and separation properties of new siliceous zeolites (such as STW, SOF, PUN, STO, SSF, RWY, LTF, IWS, ITR, SVR, BSV and SFS) were investigated by grand canonical Monte Carlo (GCMC) simulation. The force fields of COMPASS, PCFF, CVFF, DREIDING and Universal were used in the GCMC simulation to select the appropriate force field for obtaining the adsorption isotherms of methane and carbon dioxide on the purely siliceous zeolites. The simulation results by PCFF force field show a good agreement compared to the experimental data available. The adsorption isotherm of pure and binary mixtures of methane and carbon dioxide on 12 new zeolites were calculated. In addition, the effects of pressure and bulk gas composition on the selectivity of carbon dioxide/methane were examined. The results demonstrate that RWY zeolite is a good candidate for the adsorption of methane and carbon dioxide at high pressure and the adsorption of methane and carbon dioxide (mol/kg zeolite) in RWY zeolite are 6.86 and 8.79mol/kg, respectively. Also RWY zeolite is the best zeolite types for the maximum separation of binary mixture of methane and carbon dioxide.
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  PubDate: 2013-05-07T03:20:43Z
Direct synthesis, characterization and application in benzaldehyde oxidation of HPWA-SBA-15 mesoporous catalysts
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Bei-Bei Dong , Bing-Bing Zhang , Hai-Yan Wu , Shu-Ding Li , Ke Zhang , Xiu-Cheng Zheng
  HPWA-SBA-15 mesoporous catalysts were prepared via directly introducing 12-tungstophosphoric acid (HPWA) into SBA-15 by a hydrothermal method. The samples were characterized by XRD, XRF, FT-IR, DR UV–vis, SEM, TEM, NH3-TPD, and nitrogen adsorption–desorption. The influence of different HPWA amounts on the structure and catalytic properties for benzaldehyde oxidation with 30wt.% H2O2 was comparatively studied. The results indicated that the HPWA-SBA-15 materials retained the mesopore structure of SBA-15 and the XRD patterns of bulk HPWA would not appear until the HPWA loading increased to 40wt.%. Catalytic performance tests revealed that HPWA-SBA-15 was an efficient catalyst for the oxidation of benzaldehyde to benzoic acid, and the sample with 35wt.% HPWA loading was found to be more active than the others under the same reaction conditions.
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  PubDate: 2013-05-07T03:20:43Z
Co(II)-tricarboxylate metal–organic frameworks constructed from solvent-directed assembly for CO2 adsorption
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Pei-Zhou Li , Xiao-Jun Wang , Yongxin Li , Quan Zhang , Rong He Desmond Tan , Wei Quan Lim , Rakesh Ganguly , Yanli Zhao
  A series of Co(II)-tricarboxylate metal–organic frameworks (MOFs), {Co3O(HBTC)2(H2O)(DMF)}n (1), {Co2(BTC)Cl(DEF)3}n (2), {Co3O(BTB)2(DMF)·2(N(CH3)2)·(H2O)}n (3), and {Co3(HCOO)(BTB)2 (DEF)·(N(C2H5)2)}n (4) (BTC=1,3,5-benzenetricarboxylate, BTB=4,4′,4″-benzene-1,3,5-triyltribenzoate, DMF= N,N′-dimethylformamide, DEF= N,N′-diethylformamide), were synthesized by solvothermal reaction in the presence of phthalic acid under different solvents (DMF and DEF). Synthetic investigations and structural analyses reveal that the two pairs of MOFs show distinct frameworks with remarkable solvent-directed feature, although they were assembled from the same starting materials, i.e., CoCl2·6H2O with tricarboxylate-BTC for 1 and 2, or with expanded derivative BTB for 3 and 4. The CO2 adsorption properties of these MOFs were investigated and the results indicate that the activated MOF 1 presents the highest CO2 uptake capability of 85.8cm3 g−1 at 1atm and 273K.
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  PubDate: 2013-05-07T03:20:43Z
Synthesis of a fully capped mesoporous silica and its hybrids with extremely low dielectric constant and loss
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Wei Shan , Lei Chen , Yang Chu , Feipeng Zhao , Guozheng Liang , Aijuan Gu , Li Yuan
  A novel fully capped mesoporous silica (FCMPS) was synthesized by producing a layer of linked polyhedral oligomeric silsesquioxanes (LPOSS) on the surface of a typical mesoporous silica (SBA-15). The structure of FCMPS was characterized using Fourier Transform Infrared (FTIR), Nuclear Magnetic Resonance (29Si NMR), X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), High Resolution Transmission Electron Microscope (HRTEM), Nitrogen adsorption–desorption and thermogravimetric (TG) analyses. Compared with SBA-15, FCMPS has not only high surface area, pore volume and size, but also remarkably improved thermal stability, the initial degradation temperature (Tdi ) of FCMPS increases about 194°C. In addition, FCMPS overcomes the drawback of SBA-15, exhibiting much lower and stable dielectric constant and loss. Based on the synthesis of FCMPS, the FCMPS/bismaleimide resin (BD) hybrids with different contents of FCMPS were prepared, and their dielectric properties were investigated. Results show that FCMPS/BD hybrids have much lower and stable dielectric constant and loss than SBA-15/BD hybrids owing to the special structure of FCMPS. With the addition of 1wt.% FCMPS into BD resin, the dielectric constant of the resultant hybrid is as low as about 2.50 over the whole frequency from 10 to 106 Hz; moreover, the dielectric loss of the hybrid is almost independent on the frequency, and the dielectric loss at higher frequencies (>103 Hz) is even lower than that of BD resin. These attractive features make FCMPS have obvious advantage in developing materials with low dielectric constant and loss.
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  PubDate: 2013-05-07T03:20:43Z
Montmorillonite based porous clay heterostructures: Influence of Zr in the structure and acidic properties
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): J.A. Cecilia , C. García-Sancho , F. Franco
  Porous clay heterostructures (PCHs) with increasing amounts of Zr were prepared from natural montmorillonite. The texture, structure and acidic properties of the obtained PCH samples were characterized by SEM, BET, XRD, FTIR, DTA-TG, NH3-TPD and 1-butene isomerization. These studies show that the addition of Zr has a noticeably effect in the structural order of the PCH along the c ∗-axis with lower influence of random displacements between layers along a and b-axis. This addition causes a decrease of the specific surface area, an increase of the density of acid sites generating Brönsted-type acidity when zirconium content increases.
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  PubDate: 2013-05-03T06:04:00Z
The role of small organic amine molecules and their aggregates in the crystallization of microporous materials
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Ran Chao , Yalu Kong , Liang Jin , Yuan Ren , Yue Ding , Niu Li , Naijia Guan , Shouhe Xiang
  A series of 1,6-hexamethylenediamine (1,6-HDA) solutions with different concentrations were prepared and used as the structure directing agents for the crystallization of microporous materials. The surface tension of these solutions has been measured to inspect the assembly behavior of 1,6-HDA molecules. It has been found that the surface tension of these solutions decrease with the increase of 1,6-HDA concentration, which is similar to what in surfactant CTAB (Cetyl trimethyl ammonium bromide) solutions. When they were used to direct the crystallization of aluminophosphites, zincophosphates, and aluminophosphates, it was found that at low concentration, 1,6-HDA molecules cannot affect the crystallization process, and three-dimensional frameworks without 1,6-HDA in it were obtained. When 1,6-HDA concentration increased, the surface tension of these solution decreased sharply, and 1,6-HDA containing three-dimensional (3-D) frameworks were formed. 1,6-HDA molecules retained in these structure were not in assembling state, but in independent state. At high 1,6-HDA concentration, the surface tension of the solutions changed slowly accompanying with the assembly of 1,6-HDA molecules. It always resulted in the formation of layered structures with the inorganic layers interleaved by composite layers of diprotonated 1,6-HDA. Formation of large-micropore containing 3-D frameworks mainly resulted from the interaction between inorganic framework and organic amine at proper ratio, not from the assembly of 1,6-HDA molecules. Otherwise, the aggregates of 1,6-HDA molecules favors the formation of layered materials.
  Graphical abstract
  
  PubDate: 2013-05-03T06:04:00Z
CO2 capture using particulate silica aerogel immobilized with tetraethylenepentamine
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Nick Linneen , Robert Pfeffer , Y.S. Lin
  A high capacity CO2 sorbent was developed using high porosity hydrophilic and hydrophobic silica aerogel impregnated with tetraethylenepentamine (TEPA). Aerogel sorbents were characterized by thermogravimetric analysis, Fourier transform infrared spectroscopy, and nitrogen adsorption porosimetry for confirming the TEPA loadings and examining the residual porosity after modification. The aerogel sorbents appear to shrink during the drying step of amine impregnation while the surface chemistry of the support is altering the TEPA distribution within the pores. The adsorption performance was tested under pure and low CO2 partial pressure conditions at 75°C where the hydrophilic aerogel sorbents outperformed the hydrophobic sorbents. The 80wt.% TEPA loaded hydrophilic sorbent achieved the largest capacity of 6.1mmol/g in pure CO2 while also attaining 3.5mmol/g under a dry 10% CO2/Ar stream. The sorbent also showed excellent cyclic stability having a working CO2 sorption capacity of 5.1mmol/g over 10 cycles.
  Graphical abstract
  
  PubDate: 2013-05-03T06:04:00Z
Molecular engineering of microporous crystals: (VII) The molar ratio dependence of the structure-directing ability of piperazine in the crystallization of four aluminophosphates with open-frameworks
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Xiaoqiang Tong , Jun Xu , Xu Li , Yi Li , Wenfu Yan , Jihong Yu , Feng Deng , Huai Sun , Ruren Xu
  The crystallization fields of initial mixtures with compositions of Al2O3:3.0 P2O5:x pip:277 H2O, where x =2.4–12 and pip=piperazine, were investigated. Pure and highly crystalline three-dimensional (3D) AlPO-CJB2, two-dimensional (2D) AP2pip, 3D AlPO-JU88, and 2D AlPO-CJ9 were obtained when x =3, 3.4, 6.5, and 12, respectively. Along with the increase in the ratio of piperazine to Al2O3 in the initial mixture, the density of piperazine in the final structure as well as the non-bonding interaction between the inorganic framework and the protonated piperazine increased. The crystallization processes of AlPO-CJB2, AP2pip, and AlPO-JU88 were investigated using multiple techniques. In the crystallization of AlPO-CJB2, a pure and highly crystalline AP2pip intermediate phase was first formed and then dissolved. A species that may promote the dissolution of AP2pip and the formation of AlPO-CJB2 was identified. Under the synthetic condition of AP2pip, however, this species was not formed; thus, the transformation of AP2pip to AlPO-CJB2 was not observed even for significantly prolonged crystallization times. Additionally, the crystallization rate of AP2pip was significantly accelerated by an increased molar ratio of the reactants with respect to the aluminum source. The results indicate that the type and concentration of the species in the liquid phase were the governing factors in determining the final products and that the formation of particular structures is energy-directed.
  Graphical abstract
  
  PubDate: 2013-05-03T06:04:00Z
Thermal detemplation of SBA-15 mesophases. Effect of the activation protocol on the framework contraction
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Zheng Zhang , Jie Yin , Hero Jan Heeres , Ignacio Melián-Cabrera
  The potential use of the solvothermal extraction (SE) as a preliminary step to calcination for detemplating SBA-15 mesophases is investigated; aiming to reduce the amount of organics to be burnt and thereby the corresponding structural shrinkage. A systematic study was carried out by soxhlet extraction on mesophases hydrothermally aged between 90 and 130°C. The mesophases containing variable amounts of template were then treated by calcination or pyrolysis/calcination. TGA was applied to quantify the template amount after the various treatments. The as obtained materials were characterized by SAXS and Ar ad/desorption for structural and textural information while 1H NMR gave information about the integrity of the as-recycled template. The study shows that solvothermal conditions remove considerably the template, typically from 50 to 10–20wt.%, mainly extracted from the primary mesopores. Possible reuse of the extracted template is questionable as it is poor in polyethyleneoxide compared to the synthesis block-copolymer, Pluronic P123. For all thermal protocols applied (direct calcination, calcination after solvent-extraction or pyrolysis/calcination after solvent extraction), the thermal shrinkage decreases with the aging temperature; that is consistent with the condensation degree of the silica. For each mesophase, it was found that the thermal shrinkage becomes less pronounced when the material is fully templated; thus the template can serve as structural support or can control the mass transfer of O2 and thereby the oxidation rate of the template burning.
  
  PubDate: 2013-04-28T17:34:36Z
Fabrication of two perovskite-type oxide nanoparticles as the new adsorbents in efficient removal of a pesticide from aqueous solutions: Kinetic, thermodynamic, and adsorption studies
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Haman Tavakkoli , Mohammad Yazdanbakhsh
  The perovskite-type LaFe0.9Co0.1O3 (LFCO1) and LaFe0.1Co0.9O3 (LFCO2) nanoparticles (NPs) were prepared via sol–gel method. The structure and morphology of NPs were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), scanning tunneling microscopy (STM), energy dispersive X-ray spectroscopy (EDX), and Brunauer–Emmett–Teller (BET). The average particle size of NPs is approximately between 20 and 40nm. The ability of calcined NPs to remove vitavax as a typical pesticide in aqueous solutions was assessed. The removal kinetic studies were conducted on LFCOs NPs with different contact time, temperatures, initial pesticide concentrations, and adsorbent doses to find the optimum conditions. The results showed both NPs can remove the vitavax from aqueous solution with a very high adsorption capacity. The removal process follows first-order kinetics and the Langmuir adsorption isotherm model. The activation energy and Arrhenius factor were obtained from temperature dependence of the rate constant. The thermodynamic parameters of the adsorption were also determined.
  Graphical abstract Highlights
  
  PubDate: 2013-04-28T17:34:36Z
Carboxyl-functionalized mesoporous silica–carbon composites as highly efficient adsorbents in liquid phase
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Patricia Valle-Vigón , Marta Sevilla , Antonio B. Fuertes
  Mesoporous silica–carbon composites functionalized with acidic oxygen groups were prepared by oxidation of a layer of carbon deposited inside the silica pores. The synthesis procedure involved the following steps: (a) removal of the silica surfactant, (b) impregnation of the silica pores with a carbon precursor, (c) carbonization and (d) oxidation with ammonium persulfate. The resulting silica–carbon composites contained around 25–30wt.% of carbonaceous matter with a high density of acid oxygen groups attached to the deposited carbon layer (i.e. –COOH, –CO and –OH). The structural characteristics of the parent silica were retained by the oxidized composite materials, which exhibit a high surface area, a large pore volume and a well-ordered porosity made up of uniform mesopores. The oxygen-functionalized silica–carbon composites were found to be excellent adsorbents of basic dyes (e.g. methylene blue) and heavy metals (i.e. Cu2+, Zn2+ and Pb2+) in aqueous media.
  Graphical abstract Highlights
  
  PubDate: 2013-04-28T17:34:36Z
QCM-D as a method for monitoring enzyme immobilization in mesoporous silica particles
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Christian Thörn , Hanna Gustafsson , Lisbeth Olsson
  Enzyme immobilization in mesoporous materials is a field of great interest, with applications in biocatalysis and biosensing. However, the actual immobilization process is not well understood and has mainly been studied by indirect measurements. The present work demonstrates a direct method for real time study of enzyme immobilization in mesoporous silica particles using quartz crystal microbalance with dissipation monitoring (QCM-D). Silica-coated sensors were grafted with amine groups followed by adsorption of small (40nm), spherical mesoporous silica particles, after which the enzyme immobilization into the mesoporous particles could be studied in real time. The influence of pH on the immobilization efficiency was studied using two different enzymes; lipase from Rhizopus oryzae and feruloyl esterase from Fusarium oxysporum. The results showed that the silica particles adsorbed readily to the amine-grafted surface. The QCM-D measurements indicated that considerably more enzyme was immobilized into mesoporous silica particles than to non-porous silica particles and to a flat silica surface. The viscoelastic effect of the immobilized enzymes was visualized by plotting the frequency shift against the corresponding dissipation. It was observed that the immobilization into the porous particles can be divided into two regimes where the first regime is suggested to represent adsorption to the outer surface and pore openings and the second regime represents further adsorption inside the pores. In summary, we demonstrated QCM-D as a novel method for understanding enzyme immobilization in mesoporous particles in real time and the approach may be of general use for studies of entrapment of molecules into porous particles.
  Graphical abstract
  
  PubDate: 2013-04-28T17:34:36Z
Hierarchically porous nickel/carbon composite monoliths prepared by sol–gel method from an ionic precursor
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Yasuki Kido , Kazuki Nakanishi , Nao Okumura , Kazuyoshi Kanamori
  Utilizing a facile sol–gel reaction accompanied by phase separation, rigid monolithic nickel hydroxide-based xerogels and nickel/carbon composites with hierarchical porosity have been successfully fabricated. In the synthetic route starting from nickel chloride as a nickel precursor, trimethylene oxide acts as a gelation initiator to increase pH in a reaction solution. In addition, poly(acrylic acid) plays a double role as a phase separation inducer and as a co-constituent with nickel hydroxide to comprise continuous gel skeletons in the micrometer range. As a result, obtained xerogels possess well-defined macropores evidenced by microscopy observation and mercury porosimetry. Subsequent heat-treatment in air led to the crystallization of NiO at 300°C, while calcination under argon flow brought about the formation of nickel/carbon (Ni/C) composites with hierarchical pores and large specific surface area at temperatures higher than 300°C. This is the first report on the preparation of rigid monolithic xerogels and metal/carbon composite with well-defined macropores based on a metal salt precursor containing “divalent” cation.
  Graphical abstract Highlights
  
  PubDate: 2013-04-28T17:34:36Z
Organic molecules of intrinsic microporosity: Characterization of novel microporous materials
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Annalaura Del Regno , Flor R. Siperstein
  Molecular simulations were used in this work to characterise a new class of microporous material: organic molecules of intrinsic microporosity (OMIMs). Molecular dynamics simulations were used to generate the material’s samples, and grand canonical Monte Carlo simulations of argon adsorption were used to ascertain the relationship between the different structures and the observed properties. Packing behavior, porosity and adsorption capacity have been determined for each system. The final density of the material, as well as the surface area and pore volume depend on the ending group’s bulkiness. Bulkier molecules lead to materials with lower densities, but it was found that the adsorption behavior is not just related to the material’s density, but also to the pore size and shape, which are determined by the way the molecules pack. The relationship between adsorption capacity and physical properties were analyzed and the role of surface area, free volume and enthalpic interaction were used to identify different adsorption regimes. It was found that the uptake of argon at low pressure is proportional to the strength of the adsorbent-adsorbate interaction while at moderate pressure it is dependent on the free volume and surface area.
  Graphical abstract
  
  PubDate: 2013-04-28T17:34:36Z
Long-lasting phosphorescence functionalization of mesoporous silica nanospheres by CaTiO3:Pr3+ for drug delivery
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Zhan-Jun Li , Yi-Juan Zhang , Hong-Wu Zhang , Hai-Xia Fu
  Long-lasting phosphorescence functionalization of the ordered mesoporous silica nanospheres (MSNs) was realized by depositing a CaTiO3:Pr3+ phosphor layer on its surface via the Pechini sol–gel process, resulting in the formation of the MSNs@CaTiO3:Pr3+ composite material. This material, which combines the mesoporous structure of MSNs and the red long-lasting phosphorescence property of CaTiO3:Pr3+, can be used as a novel functional drug delivery system. The results indicate that a CaTiO3:Pr3+ layer can be synthesized when the annealing temperature reaches 600°C and impurity phases start to appear when the annealing temperature reaches 800°C or higher. The specific surface area of MSNs@CaTiO3:Pr3+ decreases along with the increase of annealing temperature. The MSNs@CaTiO3:Pr3+ sample synthesized at 700°C has appropriate phosphorescence intensity and enough specific surface area (306m2/g) to load drug molecules. The as-synthesized MSNs@CaTiO3:Pr3+ composite material can be tracked in vivo by optical imaging in 12min after peritoneal injection. The quercetin-loaded MSNs@CaTiO3:Pr3+ system still shows the red phosphorescence of Pr3+ (614nm) after UV irradiation and possesses sustained drug release property. In addition, the phosphorescence intensity of Pr3+ increases with an increase in the cumulative released amount of quercetin in the system, making the extent of drug release easily identifiable, trackable, and monitorable by the change of phosphorescence. Our research supplies a new way to fabricate in vivo visible drug delivery system.
  Graphical abstract
  
  PubDate: 2013-04-28T17:34:36Z
Antifogging antireflective coatings on Fresnel lenses by integrating solid and mesoporous silica nanoparticles
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Gang Zhou , Junhui He , Ligang Xu
  Antifogging antireflective coatings were fabricated on Fresnel lenses by integrating solid silica nanoparticles (SSNs) and mesoporous silica nanoparticles (MSNs) via spin-coating assembly without any high temperature post-treatments. Superhydrophilicity and a maximum transmittance of 96.4% was achieved in the visible spectral range for the (MSNs)4 coating deposited on Fresnel lens. The maximum transmittance even reached as high as 98.5% in the visible spectral range for the (SSNs)1/(MSNs)2 (i.e., 1 layer of SSNs and 2 layers of MSNs) coating by using the (SSNs)1 coated Fresnel lens instead of uncoated Fresnel lens as the substrate, while superhydrophilicity was well retained. Transmission electron microscopy (TEM) was used to observe the morphology and structure of nanoparticles. Optical properties were characterized by a UV–vis–NIR spectrophotometer. Surface wettability was studied by a contact angle/interface system. Surface morphologies and structures of coatings were examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The influences of surface morphology and structure on the optical and wetting properties of coatings were also discussed. The coverage of MSNs was considered to significantly influence both the light transmission and hydrophilicity of coated Fresnel lenses.
  Graphical abstract
  
  PubDate: 2013-04-28T17:34:36Z
Synthesis, characterization and growth mechanism of mesoporous hollow carbon nanospheres by catalytic carbonization of polystyrene
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Jiang Gong , Jie Liu , Xuecheng Chen , Xin Wen , Zhiwei Jiang , Ewa Mijowska , Yanhui Wang , Tao Tang
  Mesoporous hollow carbon nanospheres (HCNs) were synthesized through the carbonization of polystyrene (PS) under the combined catalysis of organically-modified montmorillonite (OMMT)/cobalt catalyst at 700°C. The morphology, microstructure, phase structure, textural property and surface composition of the obtained mesoporous HCNs were investigated by field-emission scanning electron microscope, transmission electron microscope (TEM), high-resolution TEM, X-ray diffraction, Raman spectroscopy, N2 sorption and X-ray photoelectron spectroscopy. It was found that OMMT not only promoted the dispersion of cobalt catalyst in the PS matrix but also affected the degradation of PS into light hydrocarbons and aromatics. The lattice oxygen of the cobalt catalyst facilitated the decomposition of light hydrocarbons and aromatics into atomic carbon during the formation of the mesoporous HCNs. A possible mechanism was proposed to explain the growth of mesoporous HCNs through the carbonization of PS under the combined catalysis of OMMT/cobalt catalyst. More importantly, this approach also offers a new potential way to transform waste polymer materials into mesoporous HCNs, which may be used as catalyst supports, adsorbents, storage media and templates for the synthesis of other useful hollow materials.
  Graphical abstract Highlights
  
  PubDate: 2013-04-28T17:34:36Z
Conjugated microporous polymer with film and nanotube-like morphologies
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Dazhi Tan , Wannan Xiong , Hanxue Sun , Zhen Zhang , Wei Ma , Changgong Meng , Wenjie Fan , An Li
  Conjugated microporous polymer (CMP) composed of alternative phenylene and ethynylene units with film and nanotube-like morphologies were synthesized by 1,3,5-triethynylbenzene with 1,4-dibromobenzene and 1,3,5-tribromobenzene with 1,4-diethynylbenzene, respectively. Our work reveals that the morphology of CMP networks is greatly affected by the structure of monomers. We also investigated the wettability of the as-prepared CMP samples and their adsorption performance for organic solvents. The CMP samples show good surface superhydrophobicity and large BET surface area and pore volumes, making them the promising absorbent materials for separation and selective adsorption of organic contaminants or oil spills from water.
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  PubDate: 2013-04-28T17:34:36Z
Core–shell composites of USY@Mesosilica: Synthesis and application in cracking heavy molecules with high liquid yield
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Lixia Jia , Xiaoyan Sun , Xiuqun Ye , Chenglong Zou , Haifang Gu , Yao Huang , Guoxing Niu , Dongyuan Zhao
  Well core–shell composites of USY@Mesosilica with the mesoporous silica shell and little dealuminated USY zeolite core were synthesized by separating two processes of assembly and crystallization in the distinct conditions. The mesoporous silica of shell has the wormhole-like structure with large pore size and thick pore wall, as SBA-15 silica. No phase separation of mesoporous silica and USY zeolite was observed in the composites. The mesoporous shell thickness was controlled from 20nm to 60nm by adjusting the ratio of TEOS/USY from 1.26 to 2.52. The aluminium introduced composites of USY@Al-Mesosilica displayed excellent selectivity of liquid products of C5–C15 in cracking n-hexadecane at high conversion. The ratios of Liquid to Gas in the products were 0.99, 1.12 and 1.88 at the conversion of 94.83%, 86.21% and 76.64%, corresponding to the composites with the shell thickness of 20, 40 and 60nm, respectively. The ratios are much higher than that of pure USY zeolite (0.45) and the mechanical mixture of USY and AlSBA-15 (0.54). In hydrocracking Iran VGO-2 heavy oil, the NiW supported catalyst prepared from the core–shell composite of USY@Al-Mesosilica displayed excellent catalytic performances with higher activity and better selectivity than the catalyst prepared from pure USY zeolite. The core–shell composites present a potential application in hydrotreating of heavy oil.
  Graphical abstract
  
  PubDate: 2013-04-25T06:20:46Z
A simple co-nanocasting method to synthesize high surface area mesoporous LaCoO3 oxides for CO and NO oxidations
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Yongxia Wang , Xiangzhi Cui , Yongsheng Li , Zhu Shu , Hangrong Chen , Jianlin Shi
  High surface area mesoporous LaCoO3 oxides (270m2 g−1) with well crystallized perovskite framework have been successfully prepared via a simple one-step co-nanocasting method using the mesoporous SiO2 (KIT-6) template. The prepared mesoporous LaCoO3 material shows relatively high catalytic activity for CO oxidation and the complete CO conversion has been achieved at about 190°C, which is about 75°C lower than that of the non-mesoporous LaCoO3. Moreover, compared with non-mesoporous counterpart, the prepared mesoporous LaCoO3 possesses much higher catalytic activity for NO oxidation, showing rather higher NO x storage capacity. The NO removal ratio is high up to 64% under low temperature (310°C). The enhanced catalytic activity of the mesoporous LaCoO3 for CO and NO oxidation is attributed to its high surface area and crystal lattice defects. A catalytic mechanism of CO and NO oxidation was proposed.
  Graphical abstract
  
  PubDate: 2013-04-25T06:20:46Z
Facile one-step synthesis of porous ceria hollow nanospheres for low temperature CO oxidation
- Abstract: Publication date: August 2013
  Source:Microporous and Mesoporous Materials, Volume 176
  Author(s): Yang Jiao , Feifei Wang , Xiaoming Ma , Qinghu Tang , Kui Wang , Yuming Guo , Lin Yang
  Herein, porous ceria (CeO2) hollow nanospheres composed of small nanoparticles have been controllably prepared through a simple one-step solvothermal reaction without using any hard-template. The products were characterized by X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), thermogravimetric analysis (TGA), fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and N2 adsorption/desorption analysis. It was found that the porous CeO2 hollow nanospheres composed of small nanoparticles with an average diameter of 3nm have a uniform size of 135nm and a high specific surface area of 145m2/g. A self-assembly process coupled with an Ostwald ripening mechanism for the hollow structures formation was proposed based on a series of time-dependent HRTEM observations. The catalytic performance of porous CeO2 hollow nanospheres and the Au/CeO2 composite catalyst for CO oxidation were also tested. The results indicate that these porous CeO2 hollow nanospheres are excellent supports for Au nanoparticles, the CO conversion by catalysis of Au/CeO2-A composite catalyst is 92% at ambient temperature. More importantly, the CO conversion could still be reached to 91% after the catalyst had been continuously used for 20h in CO oxidation at room temperature, indicating that the Au/CeO2-A catalyst had a high catalytic activity and high durability.
  Graphical abstract
  
  PubDate: 2013-04-25T06:20:46Z
Effect of the solid pore size on the structure of polymer film at the metal oxide/polyacrylic acid solution interface – Temperature impact
- Abstract: Publication date: 15 July 2013
  Source:Microporous and Mesoporous Materials, Volume 175
  Author(s): Małgorzata Wiśniewska , Agnieszka Nosal-Wiercińska , Iwona Dąbrowska , Katarzyna Szewczuk-Karpisz
  The goal of the study was to determine the effects of adsorbent type and its pore size on the polyacrylic acid (PAA) adsorption mechanism on the solid surface in the temperature range 15–40°C. The following metal oxides were applied: aluminum (III) oxide, silicon (IV) oxide, zirconium (IV) oxide and controlled porosity glass (CPG). PAA adsorption characteristics at the metal oxide-aqueous solution interface was proposed based on the data obtained from the techniques: spectrophotometry, viscometry and potentiometric titration. They allowed the determination of the following parameters: the amount of adsorbed polymer, the linear dimensions of polymer chains in the solution, the thickness of the polymer adsorption layer, as well as the surface charge density of the adsorbent in the absence and presence of PAA. It was shown, that the adsorption of polyacrylic acid on the metal oxide surface proceeds through both electrostatic and hydrogen bridge interactions. Moreover, the temperature increase leads to the increase of macromolecule size, which influences the polymer adsorbed amount and the structure of its adsorption layer. It results in the increase of polymer adsorption with the temperature rise in the case of alumina, silica and CPG. For zirconia the adsorption minimum in the temperature range 25–30°C was obtained. Such behaviour of the investigated systems is caused by various pore size of the applied metal oxides.
  Graphical abstract
  
  PubDate: 2013-04-20T12:51:09Z
Laponite-derived porous clay heterostructures: III. The effect of alumination
- Abstract: Publication date: 15 July 2013
  Source:Microporous and Mesoporous Materials, Volume 175
  Author(s): Małgorzata Zimowska , Helena Pálková , Jana Madejová , Roman Dula , Katarzyna Pamin , Zbigniew Olejniczak , Barbara Gil , Ewa M. Serwicka
  Al-containing porous clay heterostructures (PCH) were synthesised from Laponite by post-synthesis alumination using aluminium isopropoxide and aluminium nitrate as Al sources (Si/Al=30 and 10). The solids were characterized with 27Al, 29Si MAS NMR, FTIR, nitrogen adsorption/desorption at −196°C, NH3 TPD-MS, pyridine adsorption monitored by FTIR and catalytic decomposition of ethanol. Alumination resulted in substitution of Al for Si in the mesoporous silica component of PCH and formation of some amount of extra lattice Al species. A more uniform distribution of Al sites was obtained with the use of the inorganic Al source. Alumination caused a decrease of textural parameters, more pronounced upon impregnation with Al-isopropoxide. The parent PCH-L possessed little capacity for sorption of basic molecules. Alumination enhanced the samples acidity. Pyridine adsorption showed that the acidity, especially at elevated temperatures, was primarily determined by the presence of Lewis acid sites. Brønsted acid centers were less abundant and rather weak. Increase of the Al loading resulted in a higher number of Brønsted and Lewis acid sites. For a similar level of doping, more acid sites of both types were created with the use of Al nitrate. Significant concentration of pyridine attached via hydrogen bonding to weakly acidic hydroxyl groups was observed on all samples. The study of ethanol decomposition showed that catalytically meaningful acidic properties were associated with the presence of Brønsted and Lewis acid sites generated upon alumination. Weakly acidic hydroxyl groups did not participate in the reaction.
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  PubDate: 2013-04-17T00:39:50Z
Carbon dioxide adsorption in microwave-synthesized metal organic framework CPM-5: Equilibrium and kinetics study
- Abstract: Publication date: 15 July 2013
  Source:Microporous and Mesoporous Materials, Volume 175
  Author(s): Rana Sabouni , Hossein Kazemian , Sohrab Rohani
  The adsorption equilibrium and diffusion of CO2 in CPM-5 (crystalline porous materials) were experimentally studied using a volumetric approach at three different temperatures 273, 298, and 318K and gas pressures up to 105kPa. The Freundlich adsorption equilibrium model was applied to correlate the adsorption isotherms, and the classical microspore diffusion model was applied to obtain the adsorption kinetic curves and diffusivity of CO2 in CPM-5. The selectivity of CO2 over N2 was estimated from the single component isotherms at conditions relevant to post combustion applications (0.15bar PCO2 and 0.75bar pN2). It was found that at pressures up to 105kPa, the CPM-5 adsorbent has CO2 adsorption capacity of 3mmol/g, 2.3mmol/g, at 273K and 298K, respectively, which is significantly higher than those of MOF-5 under the same conditions. The selectivity factor was 14.2 and 16.1 at 273 and 298K, respectively. The CO2 diffusivity in CPM-5, estimated from the adsorption kinetic data measured at low pressures, are 1.86×10−12 m2/s, 7.04×10−12 m2/s, and 7.87×10−12 m2/s at 273K, 298K and 318K, respectively. The initial isosteric heat of adsorption of CO2 on the CPM-5 is 36.1kJ/mol. CPM-5 shows attractive adsorption properties as an adsorbent for separation of CO2 from flue gas.
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  PubDate: 2013-04-17T00:39:50Z
Promoting effect of vanadium on CF2Cl2 destructive sorption over nanocrystalline mesoporous MgO
- Abstract: Publication date: 15 July 2013
  Source:Microporous and Mesoporous Materials, Volume 175
  Author(s): Ekaterina V. Ilyina , Ilya V. Mishakov , Aleksey A. Vedyagin , Alexander F. Bedilo , Kenneth J. Klabunde
  The effect of vanadium present in nanocrystalline mesoporous VO x –MgO aerogels on the destructive sorption of difluorodichloromethane was studied using tapered element oscillating microbalance (TEOM), synchronous thermal analyzer (STA) and mass-spectrometric analysis of the gas phase. Vanadium incorporation in the aerogels was found to increase the MgO conversion to MgF2 and shorten the induction period of the solid-state reaction. The mechanisms of the CF2Cl2 reaction with pure and vanadium-modified nanocrystalline MgO aerogels based on the obtained data are analyzed. The obtained results suggest that the formation of nuclei related to the surface active sites is the rate-determining stage of the solid-state reaction.
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  PubDate: 2013-04-17T00:39:50Z
Nanocomposites from mesoporous silica and dimethacrylic resin
- Abstract: Publication date: 15 July 2013
  Source:Microporous and Mesoporous Materials, Volume 175
  
  Mesoporous silica has been considered as fillers to elaborate nanocomposites polymer-silica. The organic part of conventional dental resin mixed with mesoporous silica, has been photopolymerized using visible irradiation and camphorquinone as an initiator. The porosity filling has been followed using differential scanning calorimetry, X-ray diffraction, nitrogen adsorption/desorption isotherms, scanning electronic microscopy (SEM), transmission electron microscopy (TEM), helium density measurements. The silica porous volume is completely filled with the dental resin and composites can be obtained when silica weight fraction is below 25%. Thermo-mechanical analyses have been performed showing a thermal dilatation coefficient around 80·10−6 °C−1.
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  PubDate: 2013-04-13T08:02:10Z
A novel hybrid sol–gel method for the synthesis of highly porous silica employing hyperbranched poly(ethyleneimine) as a reactive template
- Abstract: Publication date: 15 July 2013
  Source:Microporous and Mesoporous Materials, Volume 175
  
  A novel hybrid sol–gel templating route employing hyperbranched polymers for the production of nanostructured silica with tailored porosity and high specific surface area values is proposed based on the use of hyperbranched poly(ethyleneimine) both as a reactive template and as a macromolecular “porogen”. The procedure developed involves dissolution of hyperbranched poly(ethyleneimine), PEI, of two different molecular weights (5,000 and 25,000), in N,N-dimethylformamide or chloroform serving as solvents of different polarity and addition of 3-(triethoxysilyl)propyl isocyanate as a silica precursor which is also reactive towards PEI’s amino groups. The obtained triethoxysilyl functionalized macromolecules after hydrolysis and subsequent polycondensation reactions lead to the formation of a novel silica network architecture. By firing this hybrid material a silica powder of nanoporous structure and advanced textural properties is obtained. Synthetic reactions are monitored by FTIR spectroscopy, while the silica network formed after firing is characterized by TGA, low and wide-angle XRD, TEM and N2 adsorption techniques. The influence of several parameters, i.e., molecular weight of PEI, PEI/silica precursor molar ratio and solvent polarity on silica’s porosity is studied. Depending on the synthesis conditions, this novel templating route proved effective for the successful imprinting of mesoporous cavities into silica structure. In this way, nanostructures with tailor-made properties were obtained exhibiting specific surface area values varying from ∼600 to 1100m2/g and pore diameters up to around 5nm.
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  PubDate: 2013-04-13T08:02:10Z
A quantum mechanically guided view of Cd-MOF-5 from formation energy, chemical bonding, electronic structure, and optical properties
- Abstract: Publication date: 15 July 2013
  Source:Microporous and Mesoporous Materials, Volume 175
  
  A systematic investigation of the crystal structure, chemical bonding, electronic structure, formation energy, and optical properties of Cd-MOF-5 via DFT calculations is presented. The calculated bulk modulus (13.4GPa) indicates that Cd-MOF-5 is a soft material. The estimated band gap for Cd-MOF-5 is 3.6eV, indicating semiconducting behavior. Moreover, large formation enthalpy (−41kJmol−1) indicates its high stability and could be synthesizable. The systematic investigation on the optical response properties of Cd-MOF-5 will trigger the experimental efforts in this direction. The detailed chemical bonding analysis reveals the nature of bonds, i.e., Cd–O having mainly ionic interaction whereas O–C, H–C and C–C exhibit mainly covalent interactions.
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  PubDate: 2013-04-13T08:02:10Z
A combined computational and experimental study of high pressure and supercritical CO2 adsorption on Basolite MOFs
- Abstract: Publication date: 15 July 2013
  Source:Microporous and Mesoporous Materials, Volume 175
  
  Metal organic frameworks (such as commercial Basolite®) display significant promise for CO2 capture and storage. Here, in order to monitor CO2 capture of Basolite®, we combined high pressure CO2 adsorption with high-pressure FTIR and Monte Carlo simulations. We found that Basolite® C300 show an unprecedented rise in capture capacity above 25bars, as predicted by the DFT calculations. Adsorption isotherms were measured up to 200bar using a state-of-the-art magnetic suspension balance, and in-situ FTIR studies as a function of pressure allowed characterizing the preferential adsorption sites, and their occupancy with increasing pressure. Monte Carlo molecular simulations were used to infer nanoscopic information of the adsorption mechanism, showing the sorbent–CO2 interactions from structural and energetic viewpoints.
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  PubDate: 2013-04-13T08:02:10Z
Tungsten-incorporated cage-type mesoporous silicate: W-KIT-5
- Abstract: Publication date: 15 July 2013
  Source:Microporous and Mesoporous Materials, Volume 175
  
  Tungsten-incorporated cage-like cubic three-dimensional mesoporous silicate, KIT-5, was successfully synthesized by one-step direct hydrothermal synthesis procedure employing Pluronic F127 triblock copolymer as the structure directing agent under acidic conditions. The resulting material, labeled as W-KIT-5, was characterized by XRD (SAXS and WAXS), N2 sorption, HR-TEM, DR-UV–Vis, 29Si MAS NMR, Raman spectroscopy, H2-TPR and NH3-TPD to better understand the morphology, textural properties and nature of tungsten coordination. With an increase in tungsten content, the surface area decreased from 964 (for Si/W=100) to 425m2/g (Si/W=10) and the corresponding total pore volumes decreased from 0.68 to 0.42cm3/g. Interestingly, narrow pore size distributions centered around approximately 9.1nm were observed for all W-KIT-5 samples. Depending on the loading, the incorporated tungsten is shown to exist in the KIT-5 framework as well as in the extraframework position by complementary analytical techniques. The W-KIT-5 samples are also shown to possess low to medium type acid strength.
  Graphical abstract Highlights Tungsten containing cubic Fm3m symmetry (W-KIT-5) materials exhibiting narrow pore distribution and long range pore order.
  
  PubDate: 2013-04-13T08:02:10Z
Effects of synthesis parameters on zeolite templated carbon for hydrogen storage application
- Abstract: Publication date: 15 July 2013
  Source:Microporous and Mesoporous Materials, Volume 175
  
  Templated carbon was synthesized using NH4Y-zeolite template and furfuryl alcohol as carbon precursor by carbonization method. The effects of synthesis conditions, such as carbonization temperature, dwelling time, heating ramp and flow rate of N2, on surface area and pore structure of templated carbons were investigated. The carbonization temperature was varied in range of 650–850°C and dwelling time in range of 1–4h. Physicochemical properties of zeolite and templated carbons were studied by TGA, surface area and pore analysis, XRD, SEM and FESEM techniques. The BET and micropore area increased with increasing dwelling time and were maximum at 3h at all carbonization temperatures. At 3h dwelling time, BET surface area and pore volume of templated carbons were observed to be highest at carbonization temperature of 750°C while micropore area was slightly higher at 650°C. The hydrogen storage capacity was measured by temperature programmed desorption method at atmospheric pressure and different temperatures (−100°C and −50°C). For carbons prepared by continuous heating, hydrogen storage was maximum (0.15wt.%) at −100°C and atmospheric pressure for carbon synthesized at 650°C and 3h dwelling time. The stepwise heating resulted in higher BET surface area (1886m2/g) and micropore area (1136m2/g) and increased hydrogen uptake of 0.29wt.% at −100°C was obtained for carbon synthesized at 750°C with 3h dwelling time. The storage capacity was observed to be higher for samples having higher amount of micropores and mesopores less than 6nm.
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  PubDate: 2013-04-13T08:02:10Z
Mesoporous nano rod-like γ-alumina synthesis using phenol–formaldehyde resin as a template
- Abstract: Publication date: 15 July 2013
  Source:Microporous and Mesoporous Materials, Volume 175
  
  Mesoporous nano rod-like γ-alumina with narrow pore size distribution has been successfully prepared using phenol formaldehyde polymeric resin as a template and aluminum isopropoxide as a cheap precursor. Calcination of the resulting composites at 350 and 600°C for 6h transformed the resin-boehmite to mesoporous single phase γ-alumina. The influence of phenol formaldehyde resin on the structure, texture and morphology of alumina was investigated by mean of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Brunauer–Emmett–Teller (BET) and N2 adsorption–desorption isotherm. These mesoporous aluminas have large surface area (ca. 382m2/g), 0.4cm3/g pore volume, and narrow pore size distributions. The average pore size was achieved over the range of 3.5–5.9nm depending on the ratio of alumina to resin.
  Graphical abstract Highlights Mesoporous nano rod γ-alumina with narrow pore size distribution has been successfully prepared using phenol formaldehyde polymeric resin as a template and aluminum isopropoxide as a cheap precursor.
  
  PubDate: 2013-04-13T08:02:10Z
Effectiveness of nano-scale ZSM-5 zeolite and its deactivation mechanism on catalytic cracking of representative hydrocarbons of naphtha
- Abstract: Publication date: 15 July 2013
  Source:Microporous and Mesoporous Materials, Volume 175
  
  The catalytic cracking of representative hydrocarbons of naphtha (n-hexane, cyclohexane, and methyl-cyclohexane) over ZSM-5 zeolite catalysts was examined at reaction temperatures ranging from 823K to 923K under atmospheric pressure. It was found that the Si/Al ratio of the zeolite affected the product selectivity and conversion. In order to investigate the effects of the crystal size of the ZSM-5 zeolites on catalyst lifetime, macro- and nano-scale ZSM-5 (Si/Al=150) with crystal sizes of 2300nm and 90nm, respectively, were used for the cracking of representative naphtha hydrocarbons. In the cracking of naphthenes (cyclohexane and methyl-cyclohexane), coke was readily formed from the beginning of the reaction leading to significant deactivation of the catalyst for the macro-scale ZSM-5. In contrast, the nano-scale ZSM-5 exhibited a high conversion and high light olefins yield with stable activity, regardless of the type of reactant. As a result, the application of nano-scale ZSM-5 zeolites to the catalytic cracking of naphtha was effective and gave light olefins with high yield and excellent stable activity.
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  PubDate: 2013-04-13T08:02:10Z