Directed Synthesis
of Nanoporous Coordination Solids
Department
of Chemistry and Biochemistry
Arizona State University
This is an abstract
for a poster to be presented at the
Fifth
Foresight Conference on Molecular Nanotechnology.
There will be a link from here to the full article when it is
available on the web.
The assembly of porous frameworks by linking organic and
inorganic molecular building blocks into extended 1-D, 2-D and
3-D networks offers many attractive opportunities for designing
the topology and functionalizing the pores. Currently, at least
three challenges exist in establishing the synthetic chemistry
and utility of porous coordination solids. Firstly, attempts to
prepare materials with large pores has resulted in self-inclusion
of the assembled frameworks thus preventing access to the voids.
Secondly, in cases where the achievement of open frameworks has
been possible, removal of the guest species results in the
destruction of the framework. Thirdly, the assembly reactions
often produce either poorly crystalline or amorphous solids thus
precluding their full characterization. In this presentation, our
approach to resolving these issues including our most recent
success in this direction will be outlined and discussed.
Cationic, anionic and neutral porous networks constructed from
transition metal ions and highly symmetric organic molecules such
as 4,4'-bipyridine (4,4'-bpy) and 1,3,5-benzenetricarboxylic have
been prepared. Single crystals of these materials have been
obtained by either performing the assembly reaction in gel media
or hydrothermally in the temperature range 100-150 �C.
Interpenetration has been prevented by using large
hydrogen-bonded aggregates as the guest species to fill the
voids, which has resulted in the construction of open-frameworks
having pore dimensions of up to 35 �. Molecular and ionic guests
can be removed or exchanged from the pores to allow the inclusion
of other species into the channels. In this way, channels capable
of the selective inclusion of aromatics, alcohols, and anions
have been tailored. We have found that such processes occur with
high selectivity due to the presence of coordinatively
unsaturated metal ions and weak intermolecular forces operating
within the pores. This presentation will show that 1-D, 2-D and
3-D networks can be prepared as porous solids capable of
reversible binding of guests and selective inclusion that is not
only based on shape and size of incoming guests but also on their
electronic affinity to the channels. The synthesis,
structure and inclusion properties of these solids including
strategies for decorating the channels with organic  -systems and
coordinately unsaturated metal centers will be presented.
*Corresponding Address:
Omar M. Yaghi, Department of Chemistry and Biochemistry, Arizona
State University, Tempe, AZ 85287-1604. Phone: (602) 965-0057;
Fax: (602) 965-2747. E-mail: [email protected]
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