(479h) Metal-Organic Framework With Optimal Adsorption Thermodynamics and Kinetics for CO2 Separations

Metal-Organic Framework with Optimal Adsorption Thermodynamics and Kinetics for CO₂ Separations

Youssef Belmabkhout¹, Amy Cairns¹, Ryan Luebke¹, Patrick Nugent², Stephen D. Burd², Michael. J Zaworotko² and Mohamed Eddaoudi^1,2.

¹KAUST Advanced Membranes & Porous Materials Center, Functional Material Design, Discovery and Development (FMD³)King Abdullah University of Science and Technology
4700 King Abdullah University of Science and Technology Thuwal 23955-6900 (Kingdom of Saudi Arabia)

²Department of Chemistry, University of South Florida, 4202 East Fowler Avenue, Tampa, Florida 33620, USA.

*Corresponding author email: youssef.belmabkhout@kaust.edu.sa

Metal Organic Frameworks MOFs (MOFs) is burgeoning class of materials are comprised of metals or metal clusters (“nodes”) coordinated to multi-functional organic ligands (“linkers”) and they offer myriad of surface areas up to 7000 m²/g [1]. Furthermore, the modular nature of MOMs and their use of known coordination chemistry lead to enormous diversity of structures and properties [2].   Unfortunately, though extra-large surface area and pores facilitate high gravimetric uptake of gases at low temperature and/or high pressure, they are not conducive to highly efficient separations at the relatively low pressures necessary for the capture of CO₂ particularly for post-combustion. Unsaturated metal centers (UMCs) [3] or organic amines[2] that chemically interact with CO₂ can promote enhanced binding for CO₂ but there are drawbacks: high energy costs associated with activation, regeneration and recycling of the sorbent material, especially for amines [2]; competition with water vapor, especially for UMCs [4]; selectivity tends to monotonically decrease with increased loading of sorbate.  Consequently, a sorbent with favorable CO₂ sorption kinetics and/or constant and moderate adsorption enthalpies over a wide range of CO₂ loading will permit efficient CO₂ capture from flue gas with low regeneration costs. We describe herein an approach to synergistically balance the kinetics and thermodynamics of CO₂ sorption selectivity through a crystal engineering and reticular chemistry strategy that affords control over pore functionality and size. The resulting MOFs are microporous sorbents with narrow one dimensional square channels lined by periodically arrayed SiF₆^2- (SIFSIX) anions. These MOFs exhibit exceptional CO₂ selectivity under conditions practically relevant to CO₂ separation and capture in the context of post-combustion (flue gas CO₂/N₂), pre-combustion (shifted synthesis gas stream CO₂/H₂) and natural gas upgrading (natural gas cleanup CO₂/CH₄) [5].

[1] Farha, O. K. et al. J. Am. Chem. Soc. 134, 15016-1502 (2012).

[2] Sumida, K. et al. Chem. Rev. 112, 724-781 (2012).

[3] Caskey, S. R., Wong Foy, A. G. & Matzger, A. J.. J. Am. Chem. Soc. 130, 10870-  

     10871 (2008).

[4] Kizzie, A. C., Wong Foy, A. G. & Matzger, A. J. Langmuir 27, 6368-6373 (2011).

[5] Nugent, P., Belmabkhout, Y., Burd, S. et al. Nature (2013) 10.1038/nature11893.