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

1.      Kauffman et. al. Angew. Chem. Int. Ed. 2011, 50, 10888 –10892

2.      Millward, A. R.; Yaghi, O. M. J. Am. Chem. Soc. 2005, 127, 17998.

3.      Wang, B.; Cote, A. P.; Furukawa, H.; O'Keeffe, M.; Yaghi, O. M. Nature 2008, 453, 207.

4.      Culp, J. T.; Smith, M. R.; Bittner, E.; Bockrath, B. J. Am. Chem. Soc. 2008, 130, 12427.

5.      Takamizawa, S.; Nakata, E.; Yokoyama, H. Inorg. Chem. Commun. 2003, 6, 763.

6.      Uemura, K.; Kitagawa, S.; Fukui, K.; Saito, K. J. Am. Chem. Soc. 2004, 126, 3817.

7.      Maji, T. K.; Matsuda, R.; Kitagawa, S. Nat. Mater. 2007, 6, 142.

8.      Shimomura, S.; Horike, S.; Matsuda, R.; Kitagawa, S. J. Am. Chem.Soc. 2007, 129, 10990.

9.      Snurr, R. Q.; Hupp, J. T.; Nguyen, S. T. AIChE J. 2004, 50, 1090.