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There is no doubt though that the first big application of MOFs -
storage of gases - will be highly important, given the urgency of
developing alternatives to fossil fuels for automobiles. �For hydrogen
storage, MOFs are already used, and many carmakers have these products
in prototypes,� said F�rey.
MOFs are porous materials with microscopic sized holes, resembling
honeycombs at molecular dimensions. This property of having
astronomical numbers of tiny holes within a relatively small volume
can be exploited in various ways, one of which is as a repository for
gases. Gas molecules diffuse into the MOF solid and are contained
within its pores. In the case of gas storage, MOFs offer the crucial
advantage of soaking up some of the gas pressure exerted by the
molecules. This makes hydrogen derived from non-fossil energy sources
such as fuel cells, or even genetically engineered plants, potentially
viable as a fuel for cars while the alternative of pressurised
canisters is not. The key difference is that the amount of gas stored
in a conventional cylinder at say 200 atmospheres pressure could be
accommodated in an MOF vessel of the same size at just 30 atmospheres,
which is much safer.
The porous nature of MOFs enables them to be exploited in quite
another way as catalysts to accelerate chemical reactions for a wide
variety of materials production and pharmaceutical applications,
although this field, as F�rey noted, is still in its infancy. Yet
already the field is gaining interest beyond academia from serious
companies, with a significant development at the ESF workshop being
the presence and support of German chemicals giant BASF. This in turn
has provided high endorsement of the field�s potential and has
stimulated interest from other companies, according to F�rey.
But several challenges remain before this potential can be realised,
the first one being to assemble research and development teams with
the right body of skills. As F�rey noted, many of the skills already
exist but the researchers need to expand their horizons and focus more
broadly on the big picture beyond their specialised domains. There is
also the technical challenge of learning first how these materials are
formed, and then applying the knowledge to design MOFs matched to
specific requirements. MOFs are crystalline solids that form in highly
regular patterns from solutions, just as salts and sugars do.
Researchers need to learn how to manipulate the starting conditions to
obtain just the crystalline composition and arrangement they want.
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