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 CH₄ and N₂ , but captures other competing gases (e.g. C₂ H₆ , C₃ H₈ , and CO₂ ) 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 C₂ H₆ /CH₄ , C₃ H₈ /CH₄ , CO₂ /N₂ , and CO₂ /CH₄ . Particularly, the separation time is ≈11 min g^-1 for the C₂ H₆ /CH₄ (15/85 v/v) mixture and ≈49 min g^-1 for the C₃ H₈ /CH₄ (15/85 v/v) mixture (under a flow of 2.0 mL min^-1 ), respectively, enabling its capability for CH₄ purification from light alkanes.