Northwestern University researchers have broken a world record by
creating two new synthetic materials with the greatest amount of surface
areas reported to date.
Named NU-109 and NU-110, the materials belong to a class of
crystalline nanostructure known as metal-organic frameworks (MOFs) that
are promising vessels for natural gas storage for vehicles, catalysts,
and other sustainable materials chemistry.
The materials' promise lies in their vast internal surface area. If
the internal surface area of one NU-110 crystal the size of a grain of
salt could be unfolded, the surface area would cover a desktop. Put
another way, the internal surface area of one gram of NU-110 would cover
one-and-a-half football fields.
A paper describing the findings, "Metal-organic Framework Materials
with Ultrahigh Surface Areas: Is the Sky the Limit?" was published
August 20 in the Journal of the American Chemical Society.
The research team, led by Omar Farha, research associate professor of
chemistry in the Weinberg College of Arts and Sciences, has
synthesized, characterized, and computationally simulated the behavior
of the two MOFs that display the highest experimental
Brunauer-Emmett-Teller surface areas of any porous material on record,
7,000 m2/g; that is, one kilogram of the material contains an
internal surface area that could cover seven square kilometers.
(Brunauer-Emmett-Teller, or BET, is an analysis technique for measuring
the surface area of a material.)
The extremely high surface area, which is normally not accessible due
to solvent molecules that stay trapped within the pores, was achieved
using a carbon dioxide activation technique. As opposed to heating,
which can remove the solvent but also damage the MOF material, the
carbon dioxide-based technique removes the solvent gently and leaves the
pores completely intact.
The development could rapidly lead to further advances. MOFs are
composed of organic linkers held together by metal atoms, resulting in a
molecular cage-like structure. The researchers believe they may be able
to more than double the surface area of the materials by using less
bulky linker units in the materials' design.
The research comes from the labs of Joseph T. Hupp, professor of
chemistry in Weinberg, and Randall Q. Snurr, professor of chemical and
biological engineering at the McCormick School of Engineering.
Other authors include SonBinh Nguyen, professor of chemistry in
Weinberg; Ibrahim Eryazici, Nak Cheon Jeong, Brad G. Hauser, Amy A.
Sarjeant, and Christopher E. Wilmer, all of Northwestern; and A. Özgür
Yazaydın of the University of Surrey in the United Kingdom.
The MOF-designing and -synthesizing technology is being
commercialized by NuMat Technologies, a Northwestern startup that has
won more than $1 million in business plan competitions since
incorporating in February.
http://www.sciencedaily.com/releases/2012/09/120907125148.htm
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