Article

Hydrogen Storage in a Prototypical Zeolitic Imidazolate Framework-8

William Penn University, Filadelfia, Pennsylvania, United States
Journal of the American Chemical Society (Impact Factor: 12.11). 05/2007; 129(17):5314-5. DOI: 10.1021/ja0691932
Source: PubMed

ABSTRACT

Using the difference Fourier analysis of neutron powder diffraction data along with first-principles calculations, we reveal detailed structural information such as methyl group orientation, hydrogen adsorption sites, and binding energies within the nanopore structure of ZIF8 (Zn(MeIM)(2)). Surprisingly, the two strongest adsorption sites that we identified are both directly associated with the organic linkers, instead of the ZnN4 clusters, in strong contrast to classical MOFs, where the metal-oxide clusters are the primary adsorption sites. These observations are important and hold the key to optimizing this new class of ZIF materials for practical hydrogen storage applications. Finally, at high concentration H-2-loadings, ZIF8 structure is capable of holding up to 28 H-2 molecules (i.e., 4.2 wt %) in the form of highly symmetric novel three-dimensional interlinked H-2-nanoclusters with relatively short H-2-H-2 distances compared to solid H-2. Hence, ZIF compounds with robust chemical stability can be also an ideal template host-material to generate molecular nanostructures with novel properties.

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    • "An interesting approach, based on the development of new materials capable of storing hydrogen reversibly at high densities, has been demonstrated. A wide variety of materials has been studied, such as metal hydrides[2], activated carbon, carbon nano- structures[3], and crystalline nanoporous materials such as zeolite imidazolate frameworks (ZIFs)[4], covalent organic frameworks (COFs)[5,6], and metal-organic frameworks (MOFs)[7e9]. Despite the diversity of the classes of materials proposed, none of them meets the recommendations of the US Department of Energy (DOE) for the reversible storage of hydrogen at ambient conditions, which sets a target of 5.5% by weight in 2017[10]. "
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    ABSTRACT: Abstract We report here a theoretical investigation of molecular hydrogen storage on [Pb2(TETA)]·6H2O. Because of their high surface areas, Pb-based MOFs are promising hydrogen storage systems. Ab-initio calculations using density functional theory at the PBE level have been performed to explore the most energetically favorable adsorption sites, and to determine the nature of hydrogen bonding and the storage capacity. Our results show clearly that a hydrogen molecule can be adsorbed on different sites of the MOF with high adsorption energies per site of over 10 kJ/mol. [Pb2(TETA)]·6H2O exhibits significant elastic properties enabling it to store up to 21 molecules per unit cell. Furthermore, analysis of the nature of the bonding shows that these molecules are physisorbed on the surface, and, therefore, can be readily desorbed for use as fuel.
    Full-text · Article · Jan 2016 · International Journal of Hydrogen Energy
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    • "The composition and formulation of the filler and matrix of MMM materials are important aspects of achieving superior gas separation performance. A variety of polymer matrices have been employed, including: polyimides [20] [21], super glassy polymers [22], cross-linkable polymers [23] [24] [25] [26] [27], amphiphilic graft copolymers [28] [29] [30] and block copolymers [31] [32]. In particular, block copolymers are a promising matrix due to the elaborate microphase-separated structures that are possible with these materials, enabling a synergistic effect of high gas permeation properties and mechanical strength. "
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    ABSTRACT: Size-controlled zeolite imidazole frameworks (ZIF-8) with similar pore structures and surface areas were synthesized by altering the types of precursors and used in generating CO2 separation membranes. The use of zinc nitrate, zinc acetate and zinc chloride resulted in the formation of ZIF-8 materials that were 88, 240 and 533nm in size (ZIF-8(S), ZIF-8(M) and ZIF-8(L)), respectively. ZIF-8 particles were homogeneously distributed within a polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) block copolymer matrix without significantly destroying the microphase-separated structure of SEBS to form mixed matrix membranes (MMMs), which was confirmed via small-angle X-ray scattering (SAXS), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The mutual interaction, mechanical strength and interfacial properties of the ZIF-8 filler particles and the SEBS matrix were characterized via Fourier-transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and a universal tensile machine (UTM). The introduction of ZIF-8 led to considerable enhancement in gas permeability regardless of framework dimensions. In particular, MMMs loaded to 30wt% with ZIF-8(M) exhibited approximately 2.5-fold enhancement with regard to CO2 permeability, increasing from 170.6 to 454.6Barrer (1Barrer=1×10-10cm3(STP)cmcm-2s-1cmHg-1) at 35°C without significant CO2/N2 loss (from 12.4 to 12.0) and yielded CO2/CH4 selectivity enhancement (from 4.3 to 5.4) compared to unmodified neat SEBS membranes. The high performance of MMMs based on ZIF-8(M) could be attributed to (1) the larger mass transfer resistance of SEBS/ZIF-8(S) and/or (2) the larger interfacial free volume between the polymer matrix and the inorganic filler particles of SEBS/ZIF-8(L). The efforts of this study provide insight with regard to the optimized size of ZIFs contained within microphase-separated block copolymers for the creation of highly efficient CO2 separation membranes.
    Full-text · Article · Aug 2015 · Journal of Membrane Science
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    • "In particular, zeolitic imidazolate frameworks (ZIFs) are a subclass of metal organic frameworks with zeolite or zeolitelike topologies, which possess several extraordinary features, such as chemical robustness and thermal stability [7] [8]. Among various ZIFs materials, ZIF-8 which is a tetrahedral framework formed by zinc ions and imidazolate ligands with sodalite topology is the most extensively studied [9]. Substantial works have been done on synthesizing ZIF-8 for gas sorption/separation, catalysis, electrochemical biosensor, as well as functionalized thin films, etc. [10] [11] [12] [13] [14]. "
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    ABSTRACT: In this study, zeolitic imidazolate framework-8 (ZIF-8) nanosorbent was successfully synthesized via a facile method at room temperature. The ZIF-8 nanoparticles were characterized by nitrogen sorption, powder X-ray diffraction, field emission scanning electron microscope, transmission electron microscopy and Zeta potential. The synthesized ZIF-8 nanoparticles exhibited a high surface area of 1063.5 m2/g and were of 200–400 nm in particle size. The kinetic and isotherm data of arsenic adsorption on ZIF-8 were well fitted by pseudo-second-order and Langmuir models, respectively. The maximal adsorption capacities of As(III) and As(V) were of 49.49 and 60.03 mg/g, respectively, at T = 25 °C and pH 7.0. The ZIP-8 nanoparticles were stable at neutral and basic conditions. However, large amounts of Zn2+ were released into water from the sorbent at acidic condition, which dramatically hindered the adsorption of arsenic. SO42− and NO3− had no significant effect on the arsenic adsorption while the adsorption was significantly inhibited by PO43− and CO32−. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analysis revealed that electrostatic attraction and hydroxyl and amine groups on ZIF-8 surface played vital roles in the adsorption process.
    Full-text · Article · Oct 2014 · Colloids and Surfaces A Physicochemical and Engineering Aspects
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