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Hansjurgen Holdt - One of the best experts on this subject based on the ideXlab platform.
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systematic experimental study on quantum sieving of hydrogen isotopes in Metal amide imidazolate frameworks with narrow 1 d channels
ChemPhysChem, 2019Co-Authors: Suvendu Sekhar Mondal, Alex Kreuzer, Karsten Behrens, Gisela Schutz, Hansjurgen Holdt, Michael HirscherAbstract:Quantum sieving of hydrogen isotopes is experimentally studied in isostructural Hexagonal Metal-organic frameworks having 1-D channels, named IFP-1, -3, -4 and -7. Inside the channels, different molecules or atoms restrict the channel diameter periodically with apertures larger (4.2 A for IFP-1, 3.1 A for IFP-3) and smaller (2.1 A for IFP-7, 1.7 A for IFP-4) than the kinetic diameter of hydrogen isotopes. From a geometrical point of view, no gas should penetrate into IFP-7 and IFP-4, but due to the thermally induced flexibility, so-called gate-opening effect of the apertures, penetration becomes possible with increasing temperature. Thermal desorption spectroscopy (TDS) measurements with pure H2 or D2 have been applied to study isotope adsorption. Further TDS experiments after exposure to an equimolar H2 /D2 mixture allow to determine directly the selectivity of isotope separation by quantum sieving. IFP-7 shows a very low selectivity not higher than S=2. The selectivity of the materials with the smallest pore aperture IFP-4 has a constant value of S≈2 for different exposure times and pressures, which can be explained by the 1-D channel structure. Due to the relatively small cavities between the apertures of IFP-4 and IFP-7, molecules in the channels cannot pass each other, which leads to a single-file filling. Therefore, no time dependence is observed, since the quantum sieving effect occurs only at the outermost pore aperture, resulting in a low separation selectivity.
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syntheses of two imidazolate 4 amide 5 imidate linker based Hexagonal Metal organic frameworks with flexible ethoxy substituent
CrystEngComm, 2013Co-Authors: Suvendu Sekhar Mondal, Subarna Dey, Igor A Baburin, Alexandra Kelling, Uwe Schilde, Gotthard Seifert, Christoph Janiak, Hansjurgen HoldtAbstract:A rare example of in situ linker generation with the formation of soft porous Zn- and Co-MOFs (IFP-9 and -10, respectively) is reported. The flexible ethoxy groups of IFP-9 and -10 protrude into the 1D Hexagonal channels. The gas-sorption behavior of both materials for H2, CO2 and CH4 showed wide hysteretic isotherms, typical for MOFs having a flexible substituent which can give rise to a gate effect.
Suvendu Sekhar Mondal - One of the best experts on this subject based on the ideXlab platform.
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systematic experimental study on quantum sieving of hydrogen isotopes in Metal amide imidazolate frameworks with narrow 1 d channels
ChemPhysChem, 2019Co-Authors: Suvendu Sekhar Mondal, Alex Kreuzer, Karsten Behrens, Gisela Schutz, Hansjurgen Holdt, Michael HirscherAbstract:Quantum sieving of hydrogen isotopes is experimentally studied in isostructural Hexagonal Metal-organic frameworks having 1-D channels, named IFP-1, -3, -4 and -7. Inside the channels, different molecules or atoms restrict the channel diameter periodically with apertures larger (4.2 A for IFP-1, 3.1 A for IFP-3) and smaller (2.1 A for IFP-7, 1.7 A for IFP-4) than the kinetic diameter of hydrogen isotopes. From a geometrical point of view, no gas should penetrate into IFP-7 and IFP-4, but due to the thermally induced flexibility, so-called gate-opening effect of the apertures, penetration becomes possible with increasing temperature. Thermal desorption spectroscopy (TDS) measurements with pure H2 or D2 have been applied to study isotope adsorption. Further TDS experiments after exposure to an equimolar H2 /D2 mixture allow to determine directly the selectivity of isotope separation by quantum sieving. IFP-7 shows a very low selectivity not higher than S=2. The selectivity of the materials with the smallest pore aperture IFP-4 has a constant value of S≈2 for different exposure times and pressures, which can be explained by the 1-D channel structure. Due to the relatively small cavities between the apertures of IFP-4 and IFP-7, molecules in the channels cannot pass each other, which leads to a single-file filling. Therefore, no time dependence is observed, since the quantum sieving effect occurs only at the outermost pore aperture, resulting in a low separation selectivity.
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syntheses of two imidazolate 4 amide 5 imidate linker based Hexagonal Metal organic frameworks with flexible ethoxy substituent
CrystEngComm, 2013Co-Authors: Suvendu Sekhar Mondal, Subarna Dey, Igor A Baburin, Alexandra Kelling, Uwe Schilde, Gotthard Seifert, Christoph Janiak, Hansjurgen HoldtAbstract:A rare example of in situ linker generation with the formation of soft porous Zn- and Co-MOFs (IFP-9 and -10, respectively) is reported. The flexible ethoxy groups of IFP-9 and -10 protrude into the 1D Hexagonal channels. The gas-sorption behavior of both materials for H2, CO2 and CH4 showed wide hysteretic isotherms, typical for MOFs having a flexible substituent which can give rise to a gate effect.
Ali Zavabeti - One of the best experts on this subject based on the ideXlab platform.
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Hexagonal Metal oxide monolayers derived from the Metal gas interface
Nature Materials, 2021Co-Authors: Bao Yue Zhang, Qifeng Yao, Azmira Jannat, Guanghui Ren, Matthew R Field, Xiaoming Wen, Chunhua Zhou, Ali ZavabetiAbstract:Two-dimensional (2D) crystals are promising materials for developing future nano-enabled technologies1-6. The cleavage of weak, interlayer van der Waals bonds in layered bulk crystals enables the production of high-quality 2D, atomically thin monolayers7-10. Nonetheless, as earth-abundant compounds, Metal oxides are rarely accessible as pure and fully stoichiometric monolayers owing to their ion-stabilized 'lamellar' bulk structure11-14. Here, we report the discovery of a layered planar Hexagonal phase of oxides from elements across the transition Metals, post-transition Metals, lanthanides and Metalloids, derived from strictly controlled oxidation at the Metal-gas interface. The highly crystalline monolayers, without the support of ionic dopants or vacancies, can easily be mechanically exfoliated by stamping them onto substrates. Monolayer and few-layered Hexagonal TiO2 are characterized as examples, showing p-type semiconducting properties with hole mobilities of up to 950 cm2 V-1 s-1 at room temperature. The strategy can be readily extended to a variety of elements, possibly expanding the exploration of Metal oxides in the 2D quantum regime.
William A Goddard - One of the best experts on this subject based on the ideXlab platform.
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high h2 storage of Hexagonal Metal organic frameworks from first principles based grand canonical monte carlo simulations
Journal of Physical Chemistry C, 2008Co-Authors: Sang Soo Han, William A GoddardAbstract:Stimulated by the recent report by Yaghi and co-workers of Hexagonal Metal−organic frameworks (MOF) exhibiting reversible binding of up to 7.5 wt % at 77 K and 70 bar for MOF-177 (called here IRMOF-2-24), we have predicted additional trigonal organic linkers, including IRMOF-2-60, which we calculate to bind 9.7 wt % H2 storage at 77 K and 70 bar, the highest known value for 77 K. These calculations are based on grand canonical Monte Carlo (GCMC) simulations using force fields that match accurate quantum mechanical calculations on the binding of H2 to prototypical systems. These calculations were validated by comparison to the experimental loading curve for IRMOF-2-24 at 77K. We then used the theory to predict the effect of doping Li into the Hexagonal MOFs, which leads to substantial H2 density even at ambient temperatures. For example, IRMOF-2-96-Li leads to 6.0 wt % H2 storage at 273 K and 100 bar, the first material to attain the 2010 DOE target.
Michel W. Barsoum - One of the best experts on this subject based on the ideXlab platform.
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magnetotransport in the max phases and their 2d derivatives mxenes
Materials research letters, 2017Co-Authors: Thierry Ouisse, Michel W. BarsoumAbstract:ABSTRACTHerein, we critically assess magnetotransport in the MAX phases and their 2D derivatives, MXenes. For some MAX phases, a simple, 2D Hexagonal Metal model describes weak-field magnetotransport of their nearly free electrons reasonably well. For others, experimental and/or theoretical Fermi surfaces need to be mapped—a crucial task required for true understanding. Even less is known about MXenes. The density of apparent mobile carriers in Ti3C2Tx—assuming a single-band model—is ≈1 × 1014 cm−2 (1028 cm−3), which justifies it being sometimes described as a 2D Metal. Much work is needed before a clearer picture emerges.Impact statement Magnetotransport in the MAX phases and their 2D derivatives MXene are critically reviewed for the first time. For some, a 2D Hexagonal Metal can explain magnetotransport; in others not.
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magnetotransport in the max phases and their 2d derivatives mxenes
Materials research letters, 2017Co-Authors: Thierry Ouisse, Michel W. BarsoumAbstract:ABSTRACTHerein, we critically assess magnetotransport in the MAX phases and their 2D derivatives, MXenes. For some MAX phases, a simple, 2D Hexagonal Metal model describes weak-field magnetotransport of their nearly free electrons reasonably well. For others, experimental and/or theoretical Fermi surfaces need to be mapped—a crucial task required for true understanding. Even less is known about MXenes. The density of apparent mobile carriers in Ti3C2Tx—assuming a single-band model—is ≈1 × 1014 cm−2 (1028 cm−3), which justifies it being sometimes described as a 2D Metal. Much work is needed before a clearer picture emerges.Impact statement Magnetotransport in the MAX phases and their 2D derivatives MXene are critically reviewed for the first time. For some, a 2D Hexagonal Metal can explain magnetotransport; in others not.
