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  • 1.
    Abdelhamid, Hani Nasser
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Assiut University, Egypt.
    Wilk-Kozubek, Magdalena
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). PORT Polish Center for Technology Development, Poland.
    El-Zohry, Ahmed M.
    Gómez, Antonio Bermejo
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Valiente, Alejandro
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mudring, Anja-Verena
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Luminescence properties of a family of lanthanide metal-organic frameworks2019In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 279, p. 400-406Article in journal (Refereed)
    Abstract [en]

    Two isostructural series of lanthanide metal-organic frameworks denoted as SUMOF-7II (Ln) and SUMOF-7IIB (Ln) (Ln = La, Ce, Pr, Nd, Sm, Eu, and Gd) were synthesized using4,4',4 ''-(pyridine-2,4,6-triyl)tris(benzoic acid) (H(3)L2) and a mixture of H(3)L2 and 4,4',4 ''-(benzene-1,3,5-triyl)tris(benzoic acid) (H3BTB) as linkers, respectively. Both series were characterized using powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermal analysis (TGA), and photoluminescence spectroscopy. Photoluminescence measurements show that Eu-MOFs demonstrate a red emission while Pr- and Nd-MOFs display an emission in the near-infrared (NIR) range. On the other hand, La-, Ce-, Sm- and Gd-MOFs exhibit only a ligand-centered emission. The average luminescence lifetimes in the SUMOF-7IIB series are 1.3-1.4-fold longer than the corresponding ones in the SUMOF-7II series. SUMOF-7IIs show a good photo- and thermal stability. Altogether, the properties of SUMOF-7II and SUMOF-7IIB render them promising materials for applications including sensing, biosensing, and telecommunications.

  • 2. Abdel-Magied, Ahmed F.
    et al.
    Abdelhamid, Hani Nasser
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Assuit University, Egypt.
    Ashour, Radwa M.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Forsberg, Kerstin
    Hierarchical porous zeolitic imidazolate frameworks nanoparticles for efficient adsorption of rare-earth elements2019In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 278, p. 175-184Article in journal (Refereed)
    Abstract [en]

    Hierarchical porous zeolitic imidazolate frameworks nanoparticles (ZIF-8 NPs) were synthesized at room temperature via a template-free approach under dynamic conditions (stirring) using water as a solvent. The ZIF-8 NPs were evaluated as adsorbents for rare earth elements (La3+, Sm3+ and Dy3+). Adsorption equilibrium was reached after 7h and high adsorption capacities were obtained for dysprosium and samarium (430.4 and 281.1 mg g(-1), respectively) and moderate adsorption capacity for lanthanum (28.8 mg g(-1)) at a pH of 7.0. The high adsorption capacitiese, as well as the high stability of ZIF-8 NPs, make the hierarchical ZIF-8 materials as an efficient adsorbent for the recovery of La3+, Sm3+ and Dy3+ from aqueous solution.

  • 3. Asahina, Shunsuke
    et al.
    Uno, Shinobu
    Suga, Mitsuo
    Stevens, Sam
    Klingstedt, Miia
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Okano, Yasuyuki
    Kudo, Masato
    Schuth, Ferdi
    Anderson, Michael
    Adschiri, Tadafumi
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    A new HRSEM approach to observe fine structures of novel nanostructured materials2011In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 146, no 1-3, p. 11-17Article in journal (Refereed)
    Abstract [en]

    A new approach for observing fine structures of novel thin, nanostructured materials called through the employed to observe interesting features on a variety of new, catalyticallyimportant hierarchically porous rattlespheres.

  • 4.
    Atluri, Rambabu
    et al.
    Uppsala universitet.
    Bacsik, Zoltan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Garcia-Bennett, Alfonso E.
    Uppsala universitet.
    Structural variations in mesoporous materials with cubic Pm(3)over-barn symmetry2010In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 133, no 1-3, p. 27-35Article in journal (Refereed)
    Abstract [en]

    The fine structural details of mesoporous materials possessing Pmn symmetry prepared with varying amphiphilic surfactants under acid and alkaline conditions are investigated using electron crystallography and sorption studies. The structural data derived is used to understand the parameters that govern the formation of cavity–windows and to propose synthetic strategies in order to control independently the size of the cavities and cavity–windows. Results support that whilst attainment of Pmn cubic packing is due to the overall surfactant geometry, the formation of cavity–windows is associated with the hydration layer formed at the interphase between the surfactant and the silica wall. The charge density at the micelle surface may be tailored using two strategies: (i) using dicationic gemini surfactants at low pHs resulting in an increase in the hydration layer; or (ii) by using co-structure directing agents such as organoalkoxysilanes which reduce the hydration layer surrounding the micelles. The latter leads to the formation of higher cavity sizes and may be useful for tuning fine structural details of mesoporous materials when considering their use in important applications such as gas separation.

  • 5.
    Aziz, Baroz
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Bacsik, Zoltán
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Quantification of chemisorption and physisorption of carbon dioxide on porous silica modified by propylamines: Effect of amine density2012In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 159, p. 42-49Article in journal (Refereed)
    Abstract [en]

    Detailed molecular aspects of carbon dioxide sorption on porous silica with different amounts of tethered and cross-linked n-propylamine groups were investigated. Infrared spectroscopy was applied to directly quantify physisorbed and chemisorbed CO2 on the amine modified silicas. The fractions of physisorbed CO2 and various chemisorbed species were determined as functions of CO2 pressure and the amine density on the modified silica. Physisorbed CO2 was a minor portion of the total CO2 uptake at low pressures, but it’s contribution increased to ∼35% at 1 bar of CO2 when the propylamine surface density was low or medium (0.87-1.67 NH2/nm2). Chemisorption of CO2 dominated when the propylamine content was high (2.74 NH2/nm2). The quantities of propylammonium propylcarbamate ion pairs increased with increasing propylamine content. At low or medium amine surface densities (0.87-1.67 NH2/nm2) this increase was approximately proportional to the amine density, but the quantity of ion pairs increased very significantly when the propylamine content was high (2.74 NH2/nm2). This dependency on amine density is consistent with the idea that a sufficiently close proximity of propylamine groups allows a formation of ion pairs. The relative fractions of carbamic acid and silylpropylcarbamate were significant for materials on which ion pairs could not form. Furthermore, the quantities of carbamic acid increased with increasing amine densities suggesting that the ion pairs have a role to stabilize the labile carbamic acid through hydrogen bonds.

  • 6. Chen, Yanping
    et al.
    Su, Jie
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Huang, Shiliang
    Liang, Jie
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Peking University, China.
    Lin, Xiaohuan
    Liao, Fuhui
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Peking University, China.
    Wang, Yingxia
    Lin, Jianhua
    Gies, Hermann
    PKU-20: A new silicogermanate constructed from sti and asv layers2016In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 224, p. 384-391Article in journal (Refereed)
    Abstract [en]

    A new silicogermanate (PKU-20) was hydrothermally synthesized using triethylisopropylammonium cation as the structure directing agent in the presence of fluoride. Its structure was determined from a combination of synchrotron single crystal X-ray diffraction and powder X-ray diffraction data. PKU-20 crystallizes in the monoclinic space group C2/m, with the lattice parameters of a = 18.5901(6) angstrom, b = 13.9118 (4) angstrom, c = 22.2614(7) angstrom and beta = 100.1514 (12)degrees. The framework of PKU-20 is constructed from an alternate stacking of sti and asv layers. The sti layer is exactly the same as that in the STI framework, while the asv layer is a new layer sliced off from the ASV framework parallel to the (112) plane. The takeout scheme of the layer is discussed on the basis of a composite building unit D4R-/au-D4R. PKU-20 possesses a two-dimensional channel system, where the 10-ring channels parallel to the [010] direction are intercrossed by 12-ring pockets along the [101] direction.

  • 7.
    Cheung, Ocean
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Jie, Su
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zoltán, Bacsik
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Jing, Li
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Samain, Louise
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Xiaodong, Zou
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Niklas, Hedin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    CO2 selective NaMg-CTS-1 and its structural formation from the titanium silicate based molecule sieve NaMg-ETS-4 upon dehydration2014In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 198, p. 63-73Article in journal (Other academic)
    Abstract [en]

    A range of titanium silicates (ETS-4 and CTS-1) with interesting gas separation properties were studied as CO2 adsorbents. Some of these adsorbents, in particular NaMg-CTS-1, showed the ability to selectively adsorb CO2-over-N2. Partially exchanged NaM-ETS-4 (M = Mg, Ca, Sr and Ba) were synthesised in the Na+ form and ion exchanged with group 2 cations. All but NaBa-ETS-4 transformed into their CTS-1 counterparts, when these partially exchanged Na-ETS-4 were dehydrated. The transformation from ETS-4 to CTS-1 was monitored and studied extensively using diffraction and spectroscopic techniques. Powder X-ray diffraction allowed us to follow the changes of the unit cell parameters occurred at different temperatures. We combined high energy X-ray total scattering (analysed by pair distribution functions – PDF analysis), electron diffraction, infrared, Raman and Nuclear Magnetic Resonance (NMR) spectroscopy to study the transformation of ETS-4 to CTS-1. We understood that under dehydration steps, there was significant disruption to the Ti–O–Ti chain along the b-axis, which occurred concurrently with the distortion of the double 3-rings alongside of these chains. These changes were partly responsible for the contraction of the ETS-4 framework (and successive transformation to CTS-1). The new information allowed us to understand the interesting structures and sorption properties of these adsorbents

  • 8.
    Cheung, Ocean
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Liu, Qingling
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bacsik, Zoltan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Silicoaluminophosphates as CO2 sorbents2012In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 156, p. 90-96Article in journal (Refereed)
    Abstract [en]

    Silicoaluminophosphates (SAPO-17, SAPO-35, SAPO-56 and SAPO-RHO) synthesised via hydrothermal means are tested for their abilities to adsorb carbon dioxide. These 8-ring microporous phosphates show high capacities to adsorb CO2. SAPO-RHO has a high uptake of CO2 and a very low uptake of N-2 due to its narrow pore window aperture at 273 K. Its significant uptake of N-2 at 77 K is rationalised by a temperature induced shrinkage effect. SAPO-56 has a slightly higher CO2 capacity (5.42 mmol/g, 273 K, 101 kPa) and is less water sensitive than zeolite 13X. Cyclic adsorption and in situ infrared spectroscopy (IR) reveal that SAPOs retain 95% of their original CO2 capacity after six cycles and that adsorption occurs via physisorption. The calculated heat of adsorption for CO2 (at 0.2-0.7 mmol/g loading) on SAPO-56 and SAPO-RHO lies in the physisorption range (similar to 35 kJ/mol). SAPOs, in particular SAPO-56 and SAPO-RHO, possess many desirable properties and are potentially good adsorbents for CO2 capture in swing adsorption processes.

  • 9.
    Gao, Chuanbo
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Formation of mesoporous Co3O4 replicas of different mesostructureswith different pore sizes2009In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 123, p. 314-323Article in journal (Refereed)
    Abstract [en]

    Mesoporous metal oxides Co3O4 are prepared via hard templating synthesis method by using various mesoporous silicas with different pore size as templates. The pore size of the mesoporous silicas with the symmetry of two-dimensional (2d)-hexagonal p6mm, bicontinuous cubic Ia-3d and Pn-3m have been controlled in the range of 6.6–10.7, 4.2–7.5 and 5.1–6.7 nm, respectively, by choosing different surfactants and co-surfactants and by adjusting either the aging temperature or the ionization degree of the surfactant. The pore size of the silica template has been considered to be an important factor that determines the mesostructure of the resulting metal oxides. It has been found that for p6mm, it is easier to replicate the mesoporous symmetry at large size of mesopores. For Ia-3d, at large-pore size two sets of bicontinuous meso-channels are replicated into mesoporous Co3O4, while small-pore Ia-3d leads to replication of both one set and two sets of meso-channels. Co3O4 can replicate both one set and two sets of bicontinuous Pn-3m meso-channels at all pore sizes that can be obtained (5.1–6.7 nm), indicating the existence of ordered complementary micropores within the silica walls.

  • 10.
    Gao, Chuanbo
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Structural Chemistry.
    Izquierdo-Barba, Isabel
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Structural Chemistry.
    Nakase, Ikuhiko
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Mesostructured silica based delivery system for a drug with a peptide as a cell-penetrating vector2009In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 122, no 1-3, p. 201-207Article in journal (Refereed)
    Abstract [en]

    A drug delivery system using mesostructured silica as a reservoir has been developed for the storage and controlled release of a drug with a cell-penetrating peptide (CPP) as a vector. We use fluorescein isothiocyanate (FITC) as the drug model and octaarginine (R8) as a vector to endow the drug with cell-penetrating property. The mesostructured silica reservoir system was prepared by using a one-pot liquid?crystal templating method, which is suitable for the encapsulation of intact FITC-R8 conjugates and sustained release of drugs without hampering their properties. The hydrophobic poly(propyl oxide) (PPO) shell of the pore-filling Pluronic F127 and the electrostatic interaction between R8 and siloxide ions on the pore walls act as the diffusion-limiting factors of the FITC-R8 conjugate. A sigmoidal in vitro release of FITC-R8 from mesostructured silica into phosphate buffered saline (PBS, pH 7.4) was observed and the typical release duration was 5 days at 37 ‹C. Release from the reservoir yielded significant elongation in duration of the FITC signals in DU145 cells by confocal microscopic analysis, compared with a single administration of FITC-R8.

     

  • 11. Krüger, Martin
    et al.
    Reinsch, Helge
    Inge, Andrew Kentaro
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Stock, Norbert
    Effect of partial linker fluorination and linker extension on structure and properties of the Al-MOF CAU-102017In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 249, p. 128-136Article in journal (Refereed)
    Abstract [en]

    The systematic investigation of the solvothermal system Al3+/5-fluoroisophthalic acid (H(2)mBDC-5F)/isophthalic acid (H(2)mBDC)/DMF/H2O through a mixed-linker approach led to new mixed-linker CAU-10 derivatives containing 11, 28 and 44% of fluorinated linker molecules (denoted as CAU-10-H/F-11, CAU-10-H/F-28 and CAU-10-H/F-44, respectively), as determined by NMR spectroscopy. The crystal structure of CAU-10-H/F-28 was determined using the Rietveld method (space group 14(1)md, a = b = 21.3075(5), c = 10.7101(3) angstrom). The structure is built up by helical chains composed of cis corner-sharing AlO6 polyhedra. Each of these helices is interconnected to four adjacent helices with alternating rotational orientation through the carboxylate groups of mBDC(2-) linker molecules. Thus, accessible, square-shaped channels are formed. Sorption measurements revealed a high dependency of the adsorbed amount of gas on the degree of fluorination. With increasing fluorination, the total uptake decreases in N-2, H-2 and H2O sorption experiments and the hydrophobic character of the pores increases. In addition, an extended CAU-10 derivative, CAU-10-HTATB, was discovered using the tricarboxylic acid 4,4',4-s-triazine-2,4,6-triyl-tribenzoic acid (H(3)TATB) during the high-throughput investigation of the system Al3+/H(3)TATB/DMF/H2O. This new MOF, which was denoted CAU-10-HTATB, was thoroughly characterized using IR spectroscopy, thermogravimetric and elemental analysis, temperature dependent powder X-ray diffraction (PXRD) and sorption measurements. Although the compound is thermally stable up to 400 degrees C according to temperature-dependent PXRD measurements, it is not porous towards N2 molecules. The structure of CAU-10-HTATB could be also refined from PXRD data using the Rietveld method (space group l4(1)/a, a = b = 36.438 (1), c = 10.9373 (9) angstrom).

  • 12. Larin, Alexander V.
    et al.
    Mace, Amber
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Rybakov, Andrey A.
    Laaksonen, Aatto
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Carbonate "door" in the NaKA zeolite as the reason of higher CO2 uptake relative to N-22012In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 162, p. 98-104Article in journal (Refereed)
    Abstract [en]

    Theoretical calculations are performed on a model zeolite A where sodium ions have successively been exchanged with potassium. Using both isolated cluster and periodic DFT calculations, we made an attempt to explain how the chemisorbed carbonate species in the material contribute to the exceptionally high CO2 over N-2 selectivity of nearly 200 found in recent experiments [Liu et al. [1]] with the zeolite NaKA as adsorbent to capture and separate carbon dioxide from a gas mixture containing nitrogen. We have shown that the high carbonate forming at the potassium positions in the 8R windows (KII) results in a larger 8R window diameter potentially enhancing the CO2 uptake if adsorption is measured for individual gases.

  • 13. Li, Huachun
    et al.
    Sakamoto, Yasuhiro
    Liu, Zheng
    Ohsuna, Tetsu
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Thommes, Matthias
    Che, Shunai
    Mesoporous silicalite-1 zeolite crystals with unique pore shapes analogous to the morphology2007In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 106, no 03-jan, p. 174-179Article in journal (Refereed)
    Abstract [en]

    Thermal/hydrothermal stable silicalite-1 zeolite with high-porosity mesopores analogous to the crystal morphology has been synthesized by using large porous carbon (10-20 nm) as hard template originated from colloidal silica.

  • 14.
    Li, Yunxiang
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bernin, Diana
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gao, Feifei
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Microporous pure-silica IZM-22017In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 237, p. 222-227Article in journal (Refereed)
    Abstract [en]

    Pure-silica IZM-2 was synthesized for the first time, and the concentration of sodium hydroxide used during synthesis affected the phase purity and size of crystals. Most of the micropores in calcined pure silica IZM-2 that was synthesized in the presence of high concentrations of sodium hydroxide were inaccessible to N-2 adsorption; however, the micropores could be rendered accessible by applying either of two different post-synthetic treatments. Pure-silica IZM-2 could also be synthesized without sodium ions using the hydroxide version of the template. In this case, the micropores were accessible to N-2 directly after calcination. The size of pure-silica IZM-2 crystals obtained increased with the concentration of sodium hydroxide, with the highest concentrations giving spherical and micrometer-sized aggregates of pure-silica IZM-2 that consisted of intergrown particles (60-500 nm). The nature of the defects in pure-silica IZM-2 was studied with a combination of H-1, and Si-29 solid-state NMR spectroscopy. As expected, direct-polarization Si-29 NMR spectroscopy showed that the number of non-condensed silica groups decreased upon calcination. Calcined samples also showed broader Si-29 NMR bands for the fully condensed silica moieties, which indicated a broader distribution of bond angles and/or bond lengths. The siloxy and silanol groups in calcined pure-silica IZM-2 were accessible to protonation as determined by H-1 NMR spectroscopy. We could not determine the structure of pure-silica IZM-2 in its aggregated form; however, further studies of the synthetic conditions could yield larger, non-aggregated crystals that would facilitate structural determination.

  • 15.
    Li, Yunxiang
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Liu, Leifeng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gao, Feifei
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nanocrystalline TON-type zeolites synthesized under static conditions2018In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 256, p. 84-90Article in journal (Refereed)
    Abstract [en]

    Pure-phase zeolites of the TON-type were synthesized under static hydrothermal conditions, which previously have, typically, required stirring during synthesis. Heterocyclic structure directing agents (SDAs) were observed to play important roles in both the selection of the polymorphs as well as in affecting the morphology of the particles formed. When an imidazole-based SDA was used snowflake shaped particles formed, which indicated a dendritic growth pattern of the zeolite. These zeolite particles possessed intercrystalline mesopores. To the best of our knowledge, it is for the first time that snowflake-shaped particles have been observed for TON-type zeolites. Other synthesis parameters were optimized to obtain crystals with short c-axes. The c-axis shortened with an increased solid concentration used during synthesis. This shortening was attributed to both the degree of supersaturation, and a change of the crystal growth mechanism. Short c-axes could increase the concentration of pore mouths in TON-type zeolites. Altogether, synthesis of nanocrystalline zeolites of the TON type under static condition could, potentially, be advantageous to large-scale production.

  • 16.
    Li, Yunxiang
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zheng, Haoquan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Yun, Yifeng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bernin, Diana
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Edén, Mattias
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gao, Feifei
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    De-agglomeration of IZM-2 zeolite crystals by post-synthetic treatment2016In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 225, p. 185-191Article in journal (Refereed)
    Abstract [en]

    Highly intergrown nanocrystals are commonly observed in zeolite samples, and the densely packed agglomerates may result in small secondary porosity, which restricts the advantage of hierarchical structures. In this work we take IZM-2 zeolite as an example to demonstrate a post-treatment method with diluted hydrofluoric acid solution, which de-agglomerates intergrown zeolite nanocrystals and improves the secondary porosity. The treated samples preserve high crystallinity, similar framework composition and distinctively higher external surface area compared to the agglomerated ones. The results show that this treatment is an effective method for de-agglomeration of intergrown nanocrystals without affecting the original framework.

  • 17. Liang, Jie
    et al.
    Su, Jie
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Wang, Yingxia
    Lin, Zhongjun
    Mu, Weijun
    Zheng, Haoquan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Ruqiang
    Liao, Fuhui
    Lin, Jianhua
    CHA-type zeolites with high boron content: Synthesis, structure and selective adsorption properties2014In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 194, p. 97-105Article in journal (Refereed)
    Abstract [en]

    Borosilicate zeolites with CHA-type framework are synthesized hydrothermally by using N,N,N-trimethylcyclohexylammonium hydroxide as structure directing agent. The use of this cation induces an increase of boron content in the CHA-type zeolites, and the Si/B ratios of the as-synthesized samples is in the range of 11.8-6.9. Rietveld refinements of the calcinated samples reveal a contraction of unit cells with the increase of boron content, and the 8-ring opening window of cha cavity becomes narrower. B-11 MAS NMR shows that all the boron atoms are incorporated into the framework as tetrahedral BO4 units in the as-synthesized samples. The thermal stability of these CHA-type borosilicates decreases with the increase of boron content, and the framework can retain up to 800 degrees C. These borosilicates, with the BET surfaces of 583-632 m(2)/g, show a high adsorption capacity for H-2 at 77 K, 900 mmHg and a preferential adsorption for CO2 at 273 K. This selective adsorption property enables CHA-type borosilicates to be potential materials as CO2 adsorbent.

  • 18. Lin, S.
    et al.
    Shi, L.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ribeiro Carrott, M. M. L.
    Carrott, P. J. M.
    Rocha, J.
    Li, M. R.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, X. D.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Direct synthesis without addition of acid of Al-SBA-15 with controllable porosity and high hydrothermal stability2011In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 142, no 2-3, p. 526-534Article in journal (Refereed)
    Abstract [en]

    Using triblock copolymer Pluronic P123 as a structure-directing agent, water as solvent, tetraethyl orthosilicate (TEOS) and aluminium sulfate (Al(2)(SO(4))(3) 18H(2)O) as silica and aluminium sources, respectively, a series of Al-SBA-15 with well-ordered mesostructure has been hydrothermally synthesized up to high aging temperature through a one-step approach in an environmentally friendly mineral acid-free medium. The influence of some synthesis parameters such as Si/AI molar ratio (5-100), P123/Si molar ratio (0.0025-0.014) and aging temperature (363-443 K) on the properties of the resultant materials were investigated by powder X-ray diffraction (XRD), nitrogen adsorption-desorption at 77 K. transmission electron microscopy (TEM), and solid state (27)Al MAS NMR analyses. The textural properties of Al-SBA-15, such as specific surface area, pore volume and mesopore size, can be modified by simply adjusting those synthesis parameters. Solid state (27)Al MAS NMR results show direct evidence that aluminium is introduced onto the wall structure and located mainly at tetrahedrally coordinated sites. The structural ordering increases with increasing aluminium sulfate amount in the gel from Si/Al of 100-5, with the aluminium species playing an important role in the formation of the ordered mesostructure. The increase of aging temperature causes widening of mesopores, which are still highly ordered upon aging at 443 K. The procedure allows the formation, up to high reaction temperature, of aluminium incorporated SBA-15 exhibiting high structural ordering and hydrothermal stability.

  • 19.
    Lund, Kristina
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Muroyama, Norihiro
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Accidental extinction in powder XRD intensity of porous crystals: Mesoporous carbon crystal CMK-5 and layered zeolite-nanosheets2010In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 128, no 03-jan, p. 71-77Article in journal (Refereed)
    Abstract [en]

    CMK-5 mesoporous carbon crystals with p6mm symmetry and different carbon-wall thicknesses were prepared using furfuryl alcohol. We clearly observed that the XRD intensity of the 10 reflection diminishes at a certain thickness of carbon-wall, i.e., an ""accidental extinction"" happens in CMK-5. In order to make clear the condition of the ""accidental extinction"", XRD intensity is analytically formulated/calculated for two-dimensional system with p6mm symmetry. The conditions for the ""accidental extinction"" for the I I and 20 reflections as well as for the 10 reflection in CMK-5 were clarified. Pore diameter and carbon wall thickness were measured independently by N-2 gas adsorption isotherm and TEM images as a function of the carbon-loading, and we confirmed internal consistency between the observations and calculation for the ""accidental extinction"". Similarly it was pointed out through analytical formulation for one-dimensional system such as layered zeolite-nanosheets that the ""accidental extinction"" could be observed for the order (I > I) at the certain conditions. It was shown as a whole that knowledge of occurrence of the ""accidental extinction"" not only will prevent from determining false symmetry but also will provide internal structural information. 

  • 20.
    Ng, Jovice Boon Sing
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Vasiliev, Petr
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    The radial dependence of the spatial mesostructure of monodisperse mesoporous silica spheres2008In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 112, p. 589-596Article in journal (Refereed)
    Abstract [en]

    The pore structure of monodisperse mesostructured silica spheres has been investigated by a combination of X-ray diffraction, nitrogen sorption isotherms and transmission electron microscopy (TEM). The radial dependence of the mesostructure has been obtained by TEM analysis of thin microtomed slices taken at different distance from the particle core. A structural model is proposed based on the TEM observations where bundles of the hexagonally ordered cylindrical channels bend and twist, without any preferred direction, close to the particle core and attain a radially extended structure closer to the particle surface. Thermal calcination results in a pore shrinkage of about 16% and some loss of the long-range mesostructure while radiative disintegration and partial removal of the organic template by an UV/Ozone treatment had a negligible effect on the inorganic framework in terms of pore size or spatial pore arrangement.

  • 21.
    Ojwang, Dickson O.
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Grins, Jekabs
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Svensson, Gunnar
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    The adsorption kinetics of CO2 on copper hexacyanoferrate studied by thermogravimetric analysis2018In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 272, p. 70-78Article in journal (Refereed)
    Abstract [en]

    The CO2 adsorption and CO2 adsorption kinetics were evaluated by thermogravimetry on two Prussian blue analogues, K2x/3CuII [Fe-x(II) Fe-1-x(III) (CN)(6)](2/3), with nominally K-free x = 0.0 and K-rich x = 1.0. Differential isosteric heats of adsorption were determined from adsorption isotherms using the Clausius-Clapeyron equation and integral values by differential scanning calorimetry. The average differential heats of CO2 adsorption are 28 kJ/mol for x = 0.0 and 33 kJ/mol for x = 1.0. Both compositions show small maxima in differential heat at similar to 1 mmol/g. The integral adsorption heats were determined to be 26 kJ/mol for both x = 0.0 and x = 1.0. The kinetic CO(2 )adsorption/desorption curves can be modeled by a double exponential function describing two parallel processes with different rate constants. The activation energies for CO2 adsorption on x = 0.0 were 6 (1) kJ/mol for the faster component and 16 (1) kJ/mol for the slower one, while the corresponding values for x = 1.0 were 9 (1) kJ/mol and 7 (1) kJ/mol, respectively. The maximum CO2 uptake for both compositions was found to be similar to 4.5 mmol/g, 19.8 wt%, at 1 bar and 273 K. The materials exhibited fast adsorption kinetics and stable cyclic performance at room temperature. The kinetics were slower for the samples with x = 1.0 than for x = 0.0 which may be attributed to interactions between CO2 molecules and K+ ions.

  • 22. Ren, Tie-zhen
    et al.
    Christensen, Kirsten Elvira
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Grins, Jekabs
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Jansson, Kjell
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Shi, Lei
    Edén, Mattias
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    SU-57 – An aluminosilicogermanate with a DFT topology and variable compositions2009In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 117, no 1-2, p. 285-291Article in journal (Refereed)
    Abstract [en]

    An aluminosilicogermanate with a DFT zeotype framework (denoted as SU-57) was synthesized for the first time by ethanol-assisted hydrothermal synthesis at 160 and 170 °C. The compound was characterized by single crystal and powder X-ray diffraction, scanning and transmission electron microscopy, energy dispersive spectroscopy (EDS), thermogravimetry (TG) and solid state nuclear magnetic resonance (NMR) spectroscopy. SU-57 crystallizes in space group P42/n with estimated a ≈ 10.38–10.46 Å, c ≈ 8.88–8.91 Å, V ≈ 957–975 Å3. It has variable Al–Si–Ge composition with an approximate formula |C2H10N2| [Al(SixGe1−x)O4]2 (x ≈ 0.3–0.9), which results in a super-structure originated from different cation occupancies of the two unique tetrahedral (T) sites. Single crystal X-ray structure refinements, together with results from X-ray powder diffraction (XRPD) and EDS analysis, showed that (i) the AlO4 and (Si, Ge)O4 tetrahedra are only partially ordered over the DFT framework and do not follow a strict alternating manner. (ii) Al resides predominantly on one T site and Si and Ge predominantly on the other. (iii) The Al cation concentration (Al/(Al + Si + Ge)) is nearly constant and slightly less than 50 at%, while the Si and Ge cation concentrations vary over a large range. (iv) Al and Ge occupy both T sites. The cation disorder was confirmed by 27Al and 29Si solid state NMR. TG analysis and in situ XRPD showed that SU-57 was stable up to 375 °C in N2 atmosphere.

  • 23.
    Ren, Tie-Zhen
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Yuan, Zhong-Yong
    Hu, Weikang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Single crystal manganese oxide hexagonal plates with regulated mesoporous structures2008In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 112, no 03-jan, p. 467-473Article in journal (Refereed)
    Abstract [en]

    Porous hexagonal plates of manganese oxides are prepared by a simple hydrothermal method from metal Mn foils/powders and manganese acetate precursors tinder basic conditions. The oriented aggregation-based assembly of the nanoparticles of mixed feitknechtite and hausmannite phases gave rise to well-defined hexagonal nanoplates with irregular mesopores of similar to 5 nm in size. The hexagonal plate-like morphology was retained after calcination, and mesoporous single-crystalline Mn5O8 and alpha-Mn2O3 plates were obtained after calcinations at 400 and 700 degrees C, respectively. The interior mesopores in each plate were enlarged with the increase of calcination temperature, and turned out to be regular-shaped, i.e. polyhedral or even well-defined rectangular. Furthermore, 700 degrees C-calcination led to the fusion of nanocrystals into structurally uniform alpha-Mn2O3 crystals of hexagonal plates with regular-shaped mesoporous structure. X-ray diffraction and electron diffraction, scanning and transmission electron microscopy, X-ray energy dispersive spectroscopy, and nitrogen sorption analysis were employed to characterize these porous nanoplates. Such mesoporous hexagonal nanoplates of manganese oxides with high crystallinity may have many applications.

  • 24. Serra, Elias
    et al.
    Mayoral, Alvaro
    Stockholm University.
    Sakamoto, Yasuhiro
    Stockholm University.
    Blanco, Rosa M.
    Diaz, Isabel
    Immobilization of lipase in ordered mesoporous materials: Effect of textural and structural parameters2008In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 114, no 03-jan, p. 201-213Article in journal (Refereed)
    Abstract [en]

    A systematic study dealing with the influence of several parameters oil the immobilization of lipase in ordered mesoporous materials (OMM) is presented here. In a first step, a series of OMM have been synthesized trying to cover the most relevant structures. The aim is to get variation in the key properties susceptible of influencing their behavior as lipase supports, such as the structure (cubic or hexagonal), the nature of the pores (channel-like or cage-like), the connectivity of the porous network and the pore size. Also, by following the co-condensation technique, 5-10%-methylated analogues of the pure-silica materials have been prepared. All the samples have been fully characterized with XRD, TEM (including 3D reconstruction), SEM, TGA and N-2 isotherms, and the incorporation of the organic function has been demonstrated by Si-29 NMR. All of them have been tested as supports in the immobilization of Candida antarctica Lipase B (CaLB) and the leaching of the enzyme in aqueous media evaluated. With such a systematic approach, valuable information on the influence of the textural properties and the nature of the porous network oil the yields of immobilization and enzyme desorption have been stated. Very interestingly, leaching of the enzyme can be diminished until it practically disappears without being covalently bonded to the wall, which places the ordered mesoporous materials at the starting point of a new scenario in enzyme immobilization on preexisting supports. 

  • 25.
    Su, Jie
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kapaca, Elina
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Liu, Leifeng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Georgieva, Veselina
    Wan, Wei
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Valtchev, Valentin
    Hovmöller, Sven
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Structure analysis of zeolites by rotation electron diffraction (RED)2014In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 189, p. 115-125Article in journal (Refereed)
    Abstract [en]

    Single crystal X-ray diffraction and powder X-ray diffraction (PXRD) are powerful methods for determination of unknown crystal structures including zeolites. However, these techniques have some limitations. For instance, single crystal X-ray diffraction requires large enough crystals which are often difficult to synthesize. For powder X-ray diffraction, peak indexing and intensity extraction become difficult if there exist peak broadening caused by small crystal sizes and peak overlap due to large unit cell and high symmetry. This becomes even more complicated for samples that contain more than one phase. We developed a new rotation electron diffraction (RED) method that can overcome these limitations. Almost complete three-dimensional electron diffraction datasets can be collected from micron- or nano-sized single crystals in a transmission electron microscope by combining electron beam tilt and goniometer tilt. Here, we demonstrate the power and limitations of the RED method for ab initio structure determination of four sub-micron sized zeolites, including a calcined silicalite-1, an EUO-type germanosilicate, an FER-type aluminogermanosilicate and an AST-type aluminogermanosilicate. The latter three zeolites were found in multiphasic samples. We show how the tilt range, tilt step and resolution affect the unit cell determination, structure solution and structure refinement. The EUO-, FER- and AST-type zeolites were found in two multiphasic samples in the Al-Ge-Si system, which were also characterized by PXRD and N-2 sorption.

  • 26. Taborda, Farlán
    et al.
    Wang, Zhengyang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). College of Chemistry, Jilin University, China.
    Willhammar, Tom
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Montes, Consuelo
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Synthesis of Al-Si-beta and Ti-Si-beta by the aging-drying method2012In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 150, no 1, p. 38-46Article in journal (Refereed)
    Abstract [en]

    Al-Si-beta and Ti-Si-beta were synthesized by the aging-drying method in fluoride medium without seeding and using tetraethylammonium hydroxide as organic structure-directing agent (OSDA). In the aging-drying method the gels are allowed to release some volatile species (mainly ethanol and water). Samples with molar batch composition: SiO(2):0.54TEAOH:0.7HF:xH(2)O:yM(n+)F(n)(-) (where x approximate to 10, y = 0.02, M = Al or Ti) were aged and dried during about one week. Organic solvents were added to selected aged-dried gels to determine their role as complementary OSDA. All samples were hydrothermally treated at 140 degrees C during 1-12 days. After crystallization, samples were characterized by PXRD, SEM, TGA-DTG, FTIR, atomic absorption, low temperature nitrogen adsorption, (29)Si MAS NMR and (22)Al MAS NMR. Pure and well-crystallized zeolite beta samples were obtained in all experiments performed. Polymorph A enrichments of about 69% and 64% were reached for Ti and Al loaded samples, respectively. AI-loaded samples exhibited small average crystal sizes compared with Ti-loaded samples. The incorporation of Al in the beta framework was proven by several techniques and the Al/Si ratios were similar to those of the precursor gels. However, Ti incorporation was quite low.

  • 27. Taborda, Farlán
    et al.
    Willhammar, Tom
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Wang, Zhengyang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Montes, Consuelo
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Synthesis and characterization of pure silica zeolite beta obtained by an aging-drying method2011In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 143, no 1, p. 196-205Article in journal (Refereed)
    Abstract [en]

    Pure silica zeolite beta materials were synthesized by an unconventional method of aging and drying the starting gels at room temperature followed by the conventional hydrothermal treatment. In addition, organic solvents were added to selected samples as complementary structure directing agents (SDA). The influence of the aging-drying method, complementary SDA addition and crystallization time upon the synthesis of pure silica zeolite beta were studied. Samples were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), thermogravimetric analyses (TGA) and nitrogen adsorption. Results revealed that the aging-drying process increased crystallization rate, produced crystals with unique morphology and scaled-surface and allowed polymorph A enrichments to about 68-70%. It was also found that addition of organic solvents during the thermal treatment tunes the crystal morphology but, does not affect the polymorphic enrichment.

  • 28.
    Urbonaite, Sigita
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Juarez-Galan, Juan M.
    Leis, Jaan
    Rodriguez-Reinoso, Francisco
    Svensson, Gunnar
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Porosity development along the synthesis of carbon from metal carbides2008In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 113, no 1-3, p. 14-21Article in journal (Refereed)
    Abstract [en]

    Carbide derived carbons (CDCs) are materials containing a wide range of pore size, their properties and applications being a function of the pore structure. For this reason it is important to find the relationship between synthesis parameters, such as initial carbide and temperature, and resulting structure. In this work, CDCs were prepared from VC, TiC, WC, TaC, NbC, HfC and ZrC at different temperatures and they have been characterized by means of gas adsorption. Nitrogen at −196 °C and carbon dioxide at 0 °C adsorptions were used to obtain structural information such as apparent surface area (SBET), micropore volume (Vmicro) and pore size distribution (PSD). These studies show that these parameters vary strongly depending on synthesis temperature (700–1200 °C) and initial carbide. Since the size of micropores is near the range suggested as being ideal for methane (CH4) storage, the high-pressure methane adsorption at 25 °C was performed to check the possible use of CDCs as storage material. The CH4 adsorption capacity of CDCs can compete with other carbons on a gravimetric basis, though the volumetric one is far from desired due to their low packing density.

  • 29.
    Xu, Chao
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ultramicroporous CO2 adsorbents with tunable mesopores based on polyimines synthesized under off-stoichiometric conditions2016In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 222, p. 80-86Article in journal (Refereed)
    Abstract [en]

    A series of porous polymers with ultramicropores and tunable mesopores were synthesized by condensation reaction (Schiff base) of triamine and trialdehyde monomers. They had specific surface areas and pore volumes of up to 694 m2/g and 0.67 cm3/g. The ultramicropores seemed to have been templated by the solvent (DMSO) primarily. The size of the mesopores depended strongly on the amine-to-aldehyde ratio used during synthesis. With a moderate aldehyde excess, the irregular mesopores of the porous polymers increased in size. The polymers’ capacities to adsorb CO2 were large (0.93–1.58 mmol/g at 0.15 bar and 2.20–3.28 mmol/g at 1 bar; 0 °C) due to their large ultramicropore volumes, and the estimated CO2-over-N2 selectivities were also relatively high (31-90 for CO2/N2 mixtures with 15v%/85v% at 0 °C). The uptake of CO2 on the polymers was quite rapid, and it appears advantageous to have a combination of meso- and ultramicropores in this class of polymers for applications in carbon capture and storage.

  • 30. Yan, Nana
    et al.
    Xu, Hongyi
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zhang, Wenna
    Sun, Tantan
    Guo, Peng
    Tian, Peng
    Liu, Zhongmin
    Probing locations of organic structure-directing agents (OSDAs) and host-guest interactions in CHA-type SAPO-34/442018In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 264, p. 55-59Article in journal (Refereed)
    Abstract [en]

    In this work, we have synthesized four SAPO-34/44 (framework type code: CHA) samples by utilizing different organic structure-directing agent (OSDA) such as cyclohexylamine (CA), n-butylamine (BA), diisopropylamine (DIPA), and dipropylamine (DPA). An approach combining Rietveld refinement and simulated annealing has been successfully applied to determine the location of the individual OSDA and the host (inorganic framework)-guest (OSDA) interaction. The final Rietveld refinements show that 1) one cha cage can be occupied by either two OSDAs (CA and BA) in the up-and-down arrangement or one OSDA (DIPA and DPA) in the longitudinal configuration and 2) the classical hydrogen bond between CA/BA and the inorganic framework in SAPO-44-CA and SAPO-34-BA could be identified. The host-guest interactions among these four samples are also investigated by FT-IR, which are consistent with Rietveld refinement results. The approach employed here could be applicable for the host-guest investigation in other crystalline porous materials.

  • 31.
    Zhang, Daliang
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Han, Yu
    King Abdullah Univ Sci & Technol, Adv Membranes & Porous Mat Ctr, Thuwal 239556900, Saudi Arabia.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Structure study of the tri-continuous mesoporous silica IBN-9 by electron crystallography2011In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 146, no 1-3, p. 88-96Article in journal (Refereed)
    Abstract [en]

    High resolution electron microscopy (HRTEM) has unique advantages for structural determination of nano-sized porous materials compared to X-ray diffraction, because it provides the important structure factor phase information which is lost in diffraction. Here we demonstrate the structure determination of the first tri-continuous mesoporous silica IBN-9 by electron crystallography. IBN-9 has a hexagonal unit cell with the space group P6(3)/mcm and a = 88.4 angstrom, c= 84.3 angstrom. HRTEM images taken along three main directions, [00 1], [1 (1) over bar 0] and [1 00] were combined to reconstruct the 3D electrostatic potential map, from which the tri-continuous pore structure of IBN-9 was discovered. The different steps of structure determination of unknown mesoporous structures by electron crystallography are described in details. Similar procedures can also be applied for structure determination of other porous and nonporous crystalline materials.

  • 32.
    Zheng, Haoquan
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Shaanxi University, China.
    Svengren, Henrik
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Huang, Zhehao
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Yang, Zhiyuan
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hollow titania spheres loaded with noble metal nanoparticles for photocatalytic water oxidation2018In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 264, p. 147-150Article in journal (Refereed)
    Abstract [en]

    A synthesis procedure for fabrication of hollow TiO2 spheres of mixed anatase/rutile composition loaded with noble metal nanoparticles (Au, Pt, Pd) is proposed. The materials demonstrated to be functioning photocatalysts for water oxidation. In particular nanoparticles loaded with Pd and Pt showed good catalytic activity in comparison to commercial TiO2 P25.

1 - 32 of 32
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