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Direct Hydrogen Binding to Metal Atoms in MOFs Could Lead to Boost in Storage Capacity

1 January 2007

Long
A simplified rendering of the structure of the MOF with 6.9 wt % hydrogen uptake. Details in paper referenced at end. Click to enlarge. Source: Jeffrey Long.

Chemical and Engineering News highlights three papers published in its sister publication, the Journal of the American Chemical Society, that report the first definitive evidence for hydrogen binding to open metal coordination sites in nanoporous metal-organic frameworks (MOFs).

Developing hydrogen storage systems of sufficient density for vehicles is proving to be a difficult problem. Direct binding, however, allows the hydrogen molecules to pack together more closely and may provide a major boost in storage capacity over simple hydrogen adsorption at nonmetal sites in previously prepared materials.

A team of researchers from University of California, Berkeley; General Motors (which funded the research); Purdue; NIST; University of Maryland; and Indiana University synthesized a manganese benzenetristetrazolate MOF with a previously unknown cubic topology. Crystals of the compound remain intact upon desolvation and show a total H2 uptake of 6.9 wt % at 77 K and 90 bar—at 60 g H2/L, this provides a storage density that is 85% that of liquid hydrogen. This capacity exceeds the Department of Energy’s 2010 targets of 6.0 wt % and 45 g/L.

The material exhibits a maximum isosteric heat of adsorption of 10.1 kJ/mol, the highest yet observed for a metal-organic framework. Neutron powder diffraction data demonstrate that this is directly related to H2 binding at coordinatively unsaturated Mn2+ centers within the framework. The data also showed H2 adsorption at several nonmetal pore sites.

A team of researchers in Australia and the US developed a copper benzenetricarboxylate MOF and used neutron powder diffraction to study D2 adsorption. The data revealed six distinct D2 adsorption sites in the framework, with sites at Cu2+ atoms occupied first, followed by nonmetal sites in smaller pores and then in larger pores.

Finally, a team from UC Santa Barbara, Stony Brook University and the Korea Research Institute of Chemical Technology prepared a nickel sulfoisophthalate MOF and used neutron scattering spectroscopy to identify strong metal-H2 binding sites and weaker nonmetal adsorption sites in the material.

The overall capacity for hydrogen of this material as well as the much stronger binding of hydrogen than in typical porous material represent an important step toward a possible utilization of porous media for hydrogen storage, according to the team.

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January 1, 2007 in Hydrogen, Hydrogen Storage | Permalink | Comments (5) | TrackBack (0)

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Comments

This sounds promissing for hydrogen storage. How well would this scale up I wonder? Also, anyone have any idea of ballpark cost per vehicle? I know it's early in the process, but if the materials and processes work out to some outrageous $200k USD per storage device/system....

Just thinking out loud for the most part.

no i don't think it will be costly,
no costly catalysators,
materials are involved,
synthesis step looks simple

is
1,3,5-tricyanobenzene

costly?

maybe its really a breakthrough,
77K and 90bar are not that harsh conditions

77K is very important, because liquid nitrogen could be used.

like with super conductors being able to use liquid nitrogen is a good thing;

I wonder how 'filling' a material like this vs filling a high pressure tank compares in speed? That seems to be many people's hang-up over EVs, the longer-than-usual fill times, and if this makes the fill even longer then it may not be the right stuff.

Words fail me. If you cannot get enough in a 10,000 psi cylinder, how are you going to get enough in a container filled with "nanoporous metal substrate", hydrides or other solids etc?

6.9% by weight - so the other 93.1% is dead weight.

77 Kelvin? Moe cryogenic rubbish. Really viable in a motor vehicle.

Beyond belief. Total intellectual dishonesty by all those participating in this Hydrogen charade.

Has anyone thought of using the earth to compress hydrogen? More precisely, what stops a company from running two cables down into the ocean 10,000 feet and supplying the cable with wind powered electricity, thereby producing hydrogen from the ocean at a pressure of 4454 psi. The hydrogen would be collected at depth and piped, at a collection pressure of 4454 psi, up to a surface collection station and further into existing high pressure gas distribution infrastructures.

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