From a Metal–Organic Square to a Robust and Regenerable Supramolecular Self‐assembly for Methane Purification

Abstract

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. C2H6, C3H8, 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 C2H6/CH4, C3H8/CH4, CO2/N2, and CO2/CH4. Particularly, the separation time is ≈11 min g−1 for the C2H6/CH4 (15/85 v/v) mixture and ≈49 min g−1 for the C3H8/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.

[M8L4]8+-Type Squares Self-Assembled by Dipalladium Corners and Bridging Aromatic Dipyrazole Ligands for Iodine Capture

“…The extensively developed metal-directed self-assembly has evolved as an elegant and efficient strategy for the controllable bottom-up construction of well-defined supramolecular architectures, − which are based on various noncovalent bonds, such as van der Waals, coordination, electrostatic, hydrogen, and halogen bonds. − More recently, functional supramolecular assemblies have played critical roles in catalysis, biological simulations, molecular recognition, host–guest encapsulation, anion sensing, and functional materials because of their structural diversity and excellent physical properties. − So far, all of these supramolecular assembled structures have been exquisitely designed since the 1990s for metal–organic/organometallic square macrocycles (“molecular squares”). ,− Recently, there has been strong interest in the design and function of molecular squares, − and they are widely used in various fields, such as catalysis, luminescence, and anticancer therapy due to the interesting physical and chemical properties of these architectures. − Among multidentate N-donor ligands, pyrazole ligands are often used in the self-assembly of polynuclear pyrazole-bridged ring structures with metal nodes via directional metal–ligand interactions. , In our previous studies, functional square-like metallamacrocycles were prepared via a directed self-assembly approach that exploited metal–ligand and metal–metal bonding interactions. − These macrocyclic metal assemblies have displayed attr...…”