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

• Adsorption properties on an SO2-DUT-5 MOF compared with pristine DUT-5.
• Shape selective behaviour for the SO2-DUT-5 and none for DUT-5 at low loadings.
• Selective separation of benzene for both materials at high loadings.

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 C5–C7 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.

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