(92c) CO2/N2 Separation in Metal Organic Framework Materials

CO₂/N₂ Separation in
Metal Organic Framework Materials
Perla B.
Balbuena
Department
of Chemical Engineering, Texas A&M University,
College
Station, TX 77843
In
recent years, metal-organic frameworks (MOFs), a class of nanoporous
materials, have received substantial attention due to their special adsorption
properties for gas storage and separation. 
The separation of CO₂ from N₂ present in flue gas
streams is especially significant due to the problems associated with CO₂
pollution of the atmosphere. Since gas separation is a
combination of thermodynamic and kinetic processes, both adsorption and
diffusion properties need to be taken into account. A huge challenge is that CO₂
and N₂ have similar kinetic
diameters (CO₂ 3.30 Å, N₂ 3.64 Å), making the separation
based purely on size very difficult. On the other hand, the modular nature of
the MOFs makes them attractive for introducing specific functional groups which
may enhance adsorption selectivity. 
Additional challenges are due to the chemical and thermal stability of
the framework materials and the presence of impurities in flue gas such as
water, O₂, NO_x, and SO_x. Here we review our recent computational
efforts in understanding the behavior of MOF materials for gas separations.  In particular we will refer to our results
using ab initio and density functional theory as well
as Grand Canonical Monte Carlo and classical molecular dynamics methods.  We will address important practical aspects of
MOFs such as the effect of the post-synthesis activation processes, as well as
their thermal and chemical stability.  In
addition, we will introduce a new concept based on shape selectivity for the
design of effective MOF materials.