From a Metal-Organic Square to a Robust and Regenerable Supramolecular Self-assembly for Methane Purification.

Porous supramolecular assemblies constructed by noncovalent interactions are promising for adsorptive purification of methane because of their easy regeneration. However, the poor stability arising from the weak noncovalent interactions has obstructed their practical applications. Here, we report a robust and easily regenerated polyhedron-based cationic framework assembled from a metal-organic square. This material exhibits a very low affinity for CH 4 and N 2 , but captures other competing gases (e.g. C 2 H 6 , C 3 H 8 , and CO 2 ) with a moderate affinity. These results underpin highly selective separation of a range of gas mixtures that are relevant to natural gas and industrial off-gas. Dynamic breakthrough studies demonstrate its practical separation for C 2 H 6 /CH 4 , C 3 H 8 /CH 4 , CO 2 /N 2 , and CO 2 /CH 4 . Particularly, the separation time is ≈11 min g -1 for the C 2 H 6 /CH 4 (15/85 v/v) mixture and ≈49 min g -1 for the C 3 H 8 /CH 4 (15/85 v/v) mixture (under a flow of 2.0 mL min -1 ), respectively, enabling its capability for CH 4 purification from light alkanes.