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: This paper reports for the first time in situ crystal growth of ZIF-8 on electrospun polyurethane (PU) nanofibers. In SEM images, continuous and compact ZIF-8 nanocrystals grow along electrospun PU nanofibers. The highest loading capacity of ZIF-8 on PU reaches 63%. By N2 adsorption-desorption, ZIF-8-PU shows a high surface area of 566 cm(2) g(-1). Combining the good flexibility of PU with the high adsorption properties of ZIF-8, ZIF-8-PU can be easily tailored into clothes or other forms as adsorption material. Furthermore, the gas adsorption ability of ZIF-8-PU was measured for H2, N2, O2 and CO2 at room temperature (20 °C) under different pressure gradients. The results show that the adsorption capacity of ZIF-8-PU for CO2 is nearly 11 times that for H2, 50 times that for O2 and 75 times that for N2 at 800 mmHg.
    Dalton Transactions 03/2014; · 3.81 Impact Factor
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    ABSTRACT: A molecular simulation study is reported for biofuel purification in six zeolitic imidazolate frameworks (ZIF-8, -25, -71, -90, -96 and -97) with different functional groups. For pure ethanol and water, the predicted adsorption isotherms agree fairly well with experimental data. Hydrogen bonding has an important effect on the adsorption of ethanol and water. In hydrophilic ZIFs (ZIF-90, -96 and -97) with polar groups, adsorption capacities are higher than in hydrophobic counterparts (ZIF-8, -25 and -71). The atomic charges in symmetrically functionalized ZIF-8, -25, and -71 are found to have an indiscernible effect on adsorption, in remarkable contrast to asymmetrically functionalized ZIF-90, -96 and -97. For ethanol-water mixtures representing the biofuel, the selectivity of ethanol-water drops with increasing ethanol in mixtures. It is revealed that the selectivity is determined primarily by framework hydrophobicity as well as the cage size. Among the six ZIFs, ZIF-8 exhibits the highest selectivity. This simulation study provides a microscopic insight into the adsorption of ethanol and water in various ZIFs, reveals the significant role of functional groups in governing biofuel purification, and would facilitate the development of new nanoporous materials for high-efficacy liquid separation.
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    ABSTRACT: ZIF-7, built as an assembly of ZnII centers and benzimidazolate ligands, shows prominent S-shaped isotherms upon CO2 adsorption that can be attributed to sorbate-induced gate-opening phenomena involving a narrow-to-large pore phase transition. This peculiar sorption pattern can be captured via the formulation of thermodynamic isotherms, providing a direct enthalpic and entropic view of the gate-opening process. Relying on such an approach, an energy barrier with preferential enthalpic nature for CO2 adsorption/desorption in the gate-opening region could be unveiled. Moreover, the elastic energy involved during the gate-opening process was revisited to 1.4–2.8 kJ mol−1 of solid in the temperature range 273–323 K, matching the value measured by isostatic compression of a ZIF-7_lp sample filled with DMF and showing a dominant entropic contribution.
    ChemPhysChem 05/2014; · 3.35 Impact Factor


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