Selective gas adsorption by novel pocket-like supramolecular coordination cages based on sulfonylcalix[4]arene-supported cobalt(II) and nickel(II) tetranuclear clusters and 4,4'-sulfonyldibenzoate linkers.

Rational design of the nanoporous metal-organic cages (MOCs) with tunable shapes, cavity sizes and adsorption properties is a tremendously important and emerging field, enabling the development of new, highly efficient molecular systems for the separation, storage, and transport of specific target guests. Herein, we report the synthesis and solid-state characterization of two novel isoreticular MOCs displaying a pocket-like shape, resulting from the linkage of two tetranuclear shuttlecock-like [MII4] sub-building units (M = Co and Ni), supported by sulfonylcalix[4]arene (SO2CA) in a cone conformation and four 4,4'-sulfonyldibenzoate linkers. Overall, the presence of 12 -SO2- groups, connected by 16 aryl units, allows the obtained supramolecular assemblies to be considered highly electron-deficient molecules, which are particularly appealing candidates for application as selective adsorbents. These coordination compounds, displaying pores of two distinct types with sizes of ca. 3 Å and 7 Å and BET surface areas of 271 and 409 m2 g-1 for Co- and Ni-based MOCs, respectively, demonstrate selective adsorption capacity towards industrially important gases and CO2, which is observed for the first time for SO2CA-supported MOCs of the pocket-like type.