(484a) Selective Adsorption of CO2 On Flexible Ni/Dbm-Bpy MOF

Selective
Adsorption of CO₂ on Flexible NiDBM-BPY MOF

Fan Shi^1,2,*,  Jeffrey
Culp^1,2 and Christopher Matranga¹,

(1)U.S. Department of Energy, National
Energy Technology Laboratory, Pittsburgh, PA, USA (2)URS
Corporation, South Park, PA, USA

* fan.shi@netl.doe.gov

To maintain fossil fuels as
viable energy source, carbon capture and storage technology is essential. Recent
novel sorbents for CO₂ capture ^1-3, including Metal
Organic Frameworks (MOFs), have attracted a lot of interests. Flexible MOFs
have one attractive feature that their structure become
dynamic only in the presence of suitable guests such as CO₂, CH₄,
N₂, and H₂. These flexible materials can show interesting
host-guest phenomena including crystal-crystal transformations and gated
adsorption behaviors due to the structural transitions which occur between the
guest free and guest-loaded states.^4-6 Such dynamic host-guest
behavior is particularly attractive for applications involving sorbent-based
gas separations and selective adsorption such as CO₂ and CH₄
separations.^7-9 In order to develop materials for these
applications, a detailed understanding of the adsorption mechanisms of these
flexible hosts is needed.

The material in this study
is the linear chain coordination polymer catena-bis (dibenzoylmethanato)-(4,4′-bipyridyl)nickel(II),
or referred as ?NiDBM-BPY?. This neutral
one-dimensional polymer was propagated by a bridging 4,4′-bipyridine
ligand bound to the z-axes of the nickel complexes
which were bischelated in a planar fashion by two
anionic DBM ligands. CO₂ breakthrough from
binary mixtures, including CO₂/N₂, CO₂/H₂,
and CO₂/CH₄, was performed in a fix-bed reactor with ID
of 0.375? and a length of 12?. The average particle size of NiDBM-Bpy
was around 100 mm to minimize external mass transfer limitations. The gas composition
of effluent was analyzed by a Mass Spectrometry (Pfeiffer Vacuum). The breakthrough curve of CO₂
from a fixed-bed reactor packed with NiDBM-Bpy showed
a step-shape curve, which also indicated the structure expansion above the structure
transition threshold pressure. The selectivity for CO₂ over N₂,
H₂, and CH₄ was calculated and results confirmed the
sorbent's affiliation to CO₂ than other gases.

References

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