Hydrogen storage in a prototypical zeolitic imidazolate framework-8.

NIST Center for Neutron Research, Gaithersburg, Maryland 20899-8562, USA.
Journal of the American Chemical Society (Impact Factor: 10.68). 05/2007; 129(17):5314-5. DOI: 10.1021/ja0691932
Source: PubMed
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    ABSTRACT: The demand for cost-efficient separations requires membranes with high gas flux and high selectivity which opens the path for further improvements. Mixed matrix membranes (MMMs) made from 33.3 wt % ZIF-8 in 6FDA-durene were tested at 35 °C and 3.5 atm. At 33.3 wt % loading of ZIF-8, H2, N2, O2, and CH4 gas permeabilities increased approximately 400%. Cross-linking the surface of this MMM, by reacting with ethylenediamine vapor, yielded a 10-fold increase in H2/CO2, H2/N2, and H2/CH4 selectivities with respect to 6FDA-durene, preserving 55% of the H2 permeability of 6FDA-durene. The permselective properties of the cross-linked skin of the MMM fall above the most recent permeability–selectivity trade-off lines (2008 Robeson upper bounds) for H2/CO2, H2/N2, and H2/CH4 separations. To the best of our knowledge, this is the first example of a cross-linked ZIF/polymer MMM for gas separation.
    Industrial & Engineering Chemistry Research. 05/2013; 52(21):6991–7001.
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    ABSTRACT: This work reports that noncovalent interactions can be exploited to achieve hyperbasicity of a base. A new class of superbase has been identified using paracyclophane-based carbenes that possess a proton affinity (PA) value of 1251.4 kJ/mol at the M06-2X/6-311+G**//B3LYP/6-31+G* level of theory. Noncovalent interactions such as C–H+···π and through-space π–π interactions amplify the basicity of such carbene systems by the stabilization of their protonated forms. These paracyclophane systems can be a suitable candidate for bis-protonation with the highest pKa (MeCN) value of 50.1 to date. The side phenyl ring in paracyclophane systems that is not directly involved in C–H+···π type interactions contributes to augment the basicity by through-space π–π interactions. The side ring of the paracyclophane system is involved in enhancement of the proton affinity of 19.3 kJ/mol via through-space π–π interaction. Molecular electrostatic potential (MESP) analysis shows that such noncovalent interactions can enhance the electron density at the reactive sites in suitably designed systems. The absolute minima of the MESP (Vmin) located for these carbene systems correlate well with their calculated proton affinity values. The frontier molecular orbital energy differences (HOMO–LUMO) of such carbenes also correlate well with their proton affinity results. These paracyclophane-based carbene systems can be used for selective binding of lithium ions. Such lithium decorated systems can be exploited as a molecular container for the storage of multiple dihydrogen. This is the first example of the use of lithiated organic superbases as hydrogen storage material. The calculated conceptual density functional theory-based reactivity descriptors such as electronegativity, hardness, and electrophilicity indicate the stability of these H2 trapped molecules. The calculated desorption energies per H2 molecule (ΔEDE) also indicate the recyclable property of the hydrogen storage materials.
    The Journal of Physical Chemistry C. 09/2013; 117(38):19325–19333.
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    Chemical Engineering Journal 07/2013; 228:398-404. · 3.47 Impact Factor


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