Chemists design world's lowest-density crystals for use in clean energy
Posted on Sunday, April 15, 2007 @ 22:49:02 UTC by vlad
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 Chemists at UCLA have designed new organic structures for the storage
of voluminous amounts of gases for use in alternative energy
technologies.
The research, to be published on April 13 in the journal Science,
demonstrates how the design principles of reticular chemistry have been
used to create three-dimensional covalent organic frameworks, which are
entirely constructed from strong covalent bonds and have high thermal
stability, high surface areas and extremely low densities.
The team of researchers comprises chemists from the Center for
Reticular Chemistry at UCLA’s California NanoSystems Institute and the
departments of chemistry and biochemistry at UCLA.
Led by Omar Yaghi, UCLA professor of chemistry and biochemistry,
the team has developed a class of materials in which components can be
changed nearly at will. Reticular chemistry, the brainchild of Yaghi,
is the chemistry of linking molecular building blocks by strong bonds
into predetermined structures. The principles of reticular chemistry
and the ability to construct chemical structures from these molecular
building blocks has led to the creation of new classes of materials of
exceptional variety.
The covalent organic frameworks, or COFs (pronounced "coffs"), one
of these new classes of materials, are the first crystalline porous
organic networks. A member of this series, COF-108, has the lowest
density reported of any crystalline material.
"These are the first materials ever made in which the organic
building blocks are linked by strong bonds to make covalent organic
frameworks," Yaghi said. "The key is that COFs are composed of light
elements, such as boron, carbon and oxygen, which provide thermal
stability and great functionality."
COF-108, the latest advance in reticular chemistry development, has
a high surface area, with more than 4,500 meters per gram. "One gram,
unraveled, could cover the surface area of approximately 30 tennis
courts," Yaghi said.
In the push to develop methods to control greenhouse gas emissions,
some of the biggest challenges have been finding ways to store hydrogen
for use as a fuel, to use methane as an alternative fuel, and to
capture and store carbon dioxide from power plant smokestacks before it
reaches the atmosphere. Yaghi and his colleagues believe COFs are
uniquely suited for all these applications because of their functional
flexibility and their extremely light weight and high porosity.
Through reticular chemistry, Yaghi has developed a process whereby it
is possible to utilize the arsenal of organic building blocks to
construct a large number of new COF structures whose components can be
easily designed to suit a particular application. The pore size and
pore functionality of these materials can be varied at will.
Yaghi, whose research overlaps chemistry, materials science and
engineering, is a member of the California NanoSystems Institute (CNSI)
at UCLA, which encourages cross-disciplinary collaboration to solve
problems in nanoscience and nanotechnology. Yaghi is also the director
of the Center for Reticular Chemistry at the CNSI.
"I have long been interested in making materials in a rational
way," Yaghi said. "At the beginning of my career, I always thought it
should be possible to create a predetermined chemical structure by
linking together well-defined molecules as building blocks, just as an
architect creates a blueprint prior to construction on buildings."
A year ago, Yaghi made national headlines when he and his team at
UCLA, along with colleagues at the University of Michigan, conducted
research that could lead to a hydrogen fuel that powers not only cars
but laptop computers, cellular phones, digital cameras and other
electronic devices. The findings were reported in the Journal of the
American Chemical Society in March 2006.
The materials used in that research, invented by Yaghi in the early
1990s, are called metal-organic frameworks, or MOFs, which have been
described as crystal sponges. These frameworks have nanoscale-size
openings, or pores, in which Yaghi and his colleagues can store gases —
such as hydrogen and methane — that are generally difficult to store
and transport.
BASF, a global chemical company based in Germany, has licensed the
technology and is moving forward on commercialization of MOFs.
In the fall of 2006, Yaghi was named one of the "Brilliant 10" by
Popular Science magazine, which described him as a "hydrogen
nano-architect" whose "research papers rank among the most influential
in his field." At the age of 42, Yaghi is already ranked No. 22 on the
list of the Top 100 most-cited chemists by Thomson Scientific.
Source: University of California - Los Angeles
Via: http://www.physorg.com/news95617436.html
In Other News:
H-1B ANSWER: INNOVATION, April 13
What technology company executive doesn't
champion innovation? Innovation is held up as the holy grail of high tech.
Innovation promises to better the world, raise living standards and provide a
good job for everyone.
Full story at http://www.physorg.com/news95683048.html
RESEARCHERS EXPLORE SCRAPPING INTERNET, April 13
(AP) -- Although it has
already taken nearly four decades to get this far in building the Internet, some
university researchers with the federal government's blessing want to scrap all
that and start over.
Full story at http://www.physorg.com/news95695366.html
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