TGQR 2010Q4 Report.pdf - Teragridforum.org

2.2.8
Chemistry: Molecular Simulation of Adsorption Sites in Metal-Organic Frameworks (PI:
Randall Snurr, Northwestern)
Metal-organic frameworks (MOFs) are a new class of nanoporous materials that could be
designed for a variety of purposes. For example, nanoscale pores tailored to attract a crowd of
hydrogen gas molecules, which normally like plenty of elbow room, might be one way to pack
more fuel into the tank of a hydrogen-driven vehicle or a fuel cell-powered mobile phone. Snurr
likens nanoporous materials in this case to a sponge, one self-assembled Tinker Toy fashion by
miniscule metal linker pieces and organic struts that join to form a 3-D structure laced with tiny
channels. Snurr and colleagues simulate adsorption sites in MOFs to predict how the materials
will perform.
A focus in 2010 was trying to develop or screen porous
materials for capturing CO2 from the exhaust gases of
coal-fired power plants. Carbon capture and sequestration
are widely viewed as a possible way to reduce CO2
emissions. The idea is to separate the carbon dioxide out
of flue gas from a coal-fired plant and then store the CO2
far underground in geologic formations. Snurr’s group is
modeling porous materials for their ability to separate
CO2 from the other gases in the flue gas stream. They
have developed a consistent molecular modeling method
and validated it against experimental data for 14
representative MOFs. With this validation, they are
screening large numbers of existing and hypothetical
MOFs.
In addition, the materials might be designed for potential
applications in catalysis, chemical separation and to
reduce auto emissions, among other things. Such
materials could lower the energy demands—and cost—of
energy-intensive processes, such as distillation, making
them “greener.” The materials could be useful in chiral
chemistry applications as well, for instance separating
active and inactive forms of molecules for use in drugs.
The researchers employ Monte Carlo simulations to
understand the materials and their properties, such as the
amount of molecules they adsorb, at an atomic level.
Snurr and colleagues likewise can predict the position and
orientation of adsorption sites. Their predictions match
Figure 2.8. The structure of a metal-organic
framework (MOF) with potential for use in
carbon dioxide capture systems superimposed
behind a silhouette of a coal-fired power plant.
Specially designed MOFs might be used to
separate CO2 from flue gas for storage deep
underground, keeping the CO2 out of the
atmosphere.
well with published results from experimental results using X-ray diffraction. The Monte Carlo
technique employed is particularly useful for evaluating a model with a large number of inputs
and more than a few uncertain parameters over and over again to yield an aggregate result, a
description that fits, say, an atomic-level representation of a metal-organic framework and its
guest molecules. The work uses computing resources at several TeraGrid sites, including Purdue,
NCSA and TACC. Recent papers covering the research include “Screening of Metal-Organic
Frameworks for Carbon Dioxide Capture from Flue Gas Using a Combined Experimental and
Modeling Approach," J. Am. Chem. Soc. 131, 18198-18199 (2009).
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