Gas phase adsorption of alkanes, alkenes and aromatics on the sulfone-DUT-5 Metal Organic Framework

A sulfone functionalized DUT-5 Metal Organic Framework 'SO2-DUT-5' was synthesized using 4,4'-bibenzoic acid-2,2'-sulfone linkers. Its adsorption properties were studied and compared to those of the pristine DUT-5 material. The inverse gas chromatographic method was used to study the adsorption of C-5-C-7 linear, branched and cyclic alkanes, alkenes and aromatic molecules. SO2-DUT-5 shows shape-selective behaviour in the adsorption of linear, branched and iso-alkanes, whereas DUT-5 is non-selective. The presence of sulfone groups results in both a reduced pore size and more specific interaction sites, leading to the shape-selective behaviour towards linear alkanes and the slightly elevated preference for aromatic compounds in the low coverage area. The separation of n-hexane/benzene and 1-hexene/benzene mixtures at higher coverage was studied by performing breakthrough experiments at different temperatures and pressures. A remarkable change in selectivity is observed when the loading of the adsorbing molecules increases. At low degree of pore filling, no significant separation between n-hexane/benzene or 1-hexene/benzene occurs, while at higher loading separation becomes apparent with a preferential adsorption of benzene. This separation at high loading is a result of the more favourable packing of benzene in this unidimensional pore system. (C) 2014 Elsevier Inc. All rights reserved.