Mixed gas adsorption of carbon dioxide and methane on a series of isoreticular microporous metal–organic frameworks based on 2-substituted imidazolate-4-amide-5-imidates

• Published in: Journal of materials chemistry 2012-01, Vol.22 (20), p.10221-10227
• Main Authors: Debatin, Franziska, Möllmer, Jens, Mondal, Suvendu Sekhar, Behrens, Karsten, Möller, Andreas, Staudt, Reiner, Thomas, Arne, Holdt, Hans-Jürgen
• Format: Article
• Language: English
• Subjects: Adsorption; Carbon dioxide; Constants; Isotherms; Materials selection; Mathematical models; Metal-organic frameworks; Methane; Selectivity
• ISSN: 0959-9428; 1364-5501
• DOI: 10.1039/c2jm15811f

In this work the adsorption of CO sub(2) and CH sub(4) on a series of isoreticular microporous metal-organic frameworks based on 2-substituted imidazolate-4-amide-5-imidates, IFP-1-IFP-6 (IFP = Imidazolate Framework Potsdam), is studied firstly by pure gas adsorption at 273 K. All experimental isotherms can be nicely described by using the Toth isotherm model and show the preferred adsorption of CO sub(2) over CH sub(4). At low pressures the Toth isotherm equation exhibits a Henry region, wherefore Henry's law constants for CO sub(2) and CH sub(4) uptake could be determined and ideal selectivity alpha sub(CO) sub(2)CH sub(4)has been calculated. Secondly, selectivities were calculated from mixture data by using nearly equimolar binary mixtures of both gases by a volumetric-chromatographic method to examine the IFPs. Results showed the reliability of the selectivity calculation. Values of alpha sub(CO) sub(2)CH sub(4)around 7.5 for IFP-5 indicate that this material shows much better selectivities than IFP-1, IFP-2, IFP-3, IFP-4 and IFP-6 with slightly lower selectivity alpha sub(CO) sub(2)CH sub(4)= 4-6. The preferred adsorption of CO sub(2) over CH sub(4) especially of IFP-5 and IFP-4 makes these materials suitable for gas separation application.