Desorption Studies of Hydrogen in Metal–Organic Frameworks

Panella, Barbara; Hönes, Katja; Müller, Ulrich; Trukhan, Natalia; Schubert, Markus M.; Pütter, Hermann; Hirscher, Michael

doi:10.1002/anie.200704053

Cited by 114 publications

(91 citation statements)

References 31 publications

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“…The saturation uptake was found to be proportional to the specific surface area [9,10] and to the micropore volume [10][11][12]. The pore diameter seems to have a strong influence on the average enthalpy of adsorption [13][14][15], which in turn determines the temperature dependence of the hydrogen uptake. Nevertheless, in this work a great variety of different structures is evaluated for making sure that the results about the usable capacity are representative for all materials.…”

Section: Fundamentalsmentioning

confidence: 96%

The usable capacity of porous materials for hydrogen storage

Schlichtenmayer

Hirscher

2016

Appl. Phys. A

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A large number of different porous materials has been investigated for their hydrogen uptake over a wide pressure range and at different temperature. From the absolute adsorption isotherms, the enthalpy of adsorption is evaluated for a wide range of surface coverage. The usable capacity, defined as the amount of hydrogen released between a maximum tank pressure and a minimum back pressure for a fuel cell, is analyzed for isothermal operation. The usable capacity as a function of temperature shows a maximum which defines the optimum operating temperature. This optimum operating temperature is higher for materials possessing a higher enthalpy of adsorption. However, the fraction of the hydrogen stored overall that can be released at the optimum operating temperature is higher for materials with a lower enthalpy of adsorption than for the ones with higher enthalpy.

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Section: Fundamentalsmentioning

confidence: 96%

The usable capacity of porous materials for hydrogen storage

Schlichtenmayer

Hirscher

2016

Appl. Phys. A

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“…[12,[24][25][26][27][84][85][86] In the former type, the small pores hinder diffusion of the H 2 molecules through ultramicropores of comparable size, because the interaction potential of the H 2 molecules is expected to be very strong due to the synergistic effect of the neighbouring pore walls. [19,76] Such a strong interaction leads to slow adsorption kinetics, resulting in adsorption/desorption hysteresis. On the other hand, in flexible pores, the hysteresis is attributed to additional steric hindrance caused by adjacent guests (kinetic trapping), where such slow desorption kinetics might be the result of the high H 2 loading of the porous framework at low pressures, which impedes the flexibility and window opening.…”

Section: Crystal Structures Of {[Zn(sif 6 )(Pyz) 2 ]·2meoh} N (2 ʛ 2mmentioning

confidence: 99%

“…[18] The other is pore-shape and -size design, where small pores show a relatively high affinity for H 2 . [19] On the basis of this background, we reasoned that frameworks with ultramicropores (with pore sizes smaller than 7 Å) might well contribute to gas separation and yield novel results on H 2 adsorption. Although several interpenetrated (interwoven) frameworks [12,[20][21][22][23][24][25][26][27][28][29] [30] and [Cu(SiF 6 )(4,4Ј-bpy) 2 ] n [31] with micropores of 7.5 ϫ 7.5 Å 2 and 8.0 ϫ 8.0 Å 2 , respectively.…”

Section: Introductionmentioning

confidence: 99%

Syntheses, Crystal Structures and Adsorption Properties of Ultramicroporous Coordination Polymers Constructed from Hexafluorosilicate Ions and Pyrazine

et al. 2009

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Three novel coordination polymers based on M2+ (M = Cu, Zn), pyrazine (pyz) and the SiF62– ion, [Cu(SiF6)(pyz)(H2O)2]n (1a), {[Cu(SiF6)(pyz)3]·2H2O}n (1b blabla 2H2O) and {[Zn(SiF6)(pyz)2]·2MeOH}n (2 blabla 2MeOH), have been synthesized and characterized by single‐crystal X‐ray diffraction analyses. Compound 1a forms straight one‐dimensional chains of–Cu(OH2)2–pyz–, which are bridged by SiF62– ions to produce two‐dimensional sheets. Compound 1b blabla 2H2O forms straight two‐dimensional sheets of –Cu(pyz)2–pyz– chains bridged by SiF62– ions, where perpendicularly protruding pyz planes are stacked to produce a three‐dimensional framework with 2.5 × 2.2 Å2 pores. In compound 2 blabla 2MeOH, grids of [Zn(pyz)2]n are bridged by SiF62– ions axially coordinating to Zn2+ ions to produce an open three‐dimensional framework. The 4.5 × 4.5 Å2 pores in 2 blabla 2MeOH are surrounded by pyz panels, and they remain intact after removal of solvents to give [Zn(SiF6)(pyz)2]n (2). The permanent porosity of 2 was characterized by adsorption studies with solvent vapours such as MeOH (kinetic diameter 3.8 Å), EtOH (4.3 Å), iPrOH (4.7 Å) and Me2CO (4.7 Å), showing a size‐exclusive effect at around 4.7 Å. Furthermore, the H2 adsorption/desorption isotherm of 2 at 77 K shows a sharp uptake with a slight hysteresis loop, which is attributed to both the small size of the pore and the interaction between H2 molecules and fluorine (SiF62–) atoms that are exposed on the pore surfaces. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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“…As a consequence MOFs with similar building units and network topology show, at low pressure, a storage capacity which is higher for the frameworks with smaller pores [96]. Moreover, thermal desorption studies of hydrogen adsorbed at 20 K in different MOFs indicate that the affinity between hydrogen and the MOFs is more influenced by the pore size than by the building units of the MOFs [107]. This result is obtained at hydrogen concentrations which are close to the maximum storage capacities; that is, at technologically relevant uptake values.…”

Section: Coordination Polymersmentioning

confidence: 94%

Physisorption in Porous Materials

Hirscher¹,

Panella²

2010

Handbook of Hydrogen Storage

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Physisorption or physical adsorption is the mechanism by which hydrogen is stored in the molecular form, that is, without dissociating, on the surface of a solid material. Responsible for the molecular adsorption of H 2 are weak dispersive forces, called van der Waals forces, between the gas molecules and the atoms on the surface of the solid. These intermolecular forces derive from the interaction between temporary dipoles which are formed due to the fluctuations in the charge distribution in molecules and atoms. The combination of attractive van der Waals forces and short range repulsive interactions between a gas molecule and an atom on the surface of the adsorbent results in a potential energy curve which can be well described by the Lennard-Jones Eq. (2.1).where e is the depth of the energy well, r i the distance between an H 2 molecule and a generic atom i on the surface and s the value of r i for which the potential is zero [1]. The minimum of the potential curve occurs at a distance from the surface which is approximately the sum of the van der Waals radii of the adsorbent atom and the adsorbate molecule. For microporous materials (r pore < 1 nm) [2] where the pore dimensions are comparable to the diameter of the adsorbate molecules this interaction potential is also influenced by the pore shape and the pore dimensions. Adsorption is an exothermic process, that is, heat is released during the adsorption of gas molecules on a surface. Owing to the low polarizability of the H 2 molecule this type of interaction is very weak and leads to low values of the heat of adsorption, typically in the range of 1-10 kJ mol À1 [3]. Compared to chemisorption which involves a change in the chemical nature of the H 2 molecule by, for example, dissociation, physisorption has approximately a ten times smaller heat of adsorption. Chemical hydrides and complex hydrides, which store hydrogen chemically, both have the disadvantage of producing an excessive amount of heat during fast Handbook of Hydrogen Storage. Edited by Michael Hirscher

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Desorption Studies of Hydrogen in Metal–Organic Frameworks

Cited by 114 publications

References 31 publications

The usable capacity of porous materials for hydrogen storage

The usable capacity of porous materials for hydrogen storage

Syntheses, Crystal Structures and Adsorption Properties of Ultramicroporous Coordination Polymers Constructed from Hexafluorosilicate Ions and Pyrazine

Physisorption in Porous Materials

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