Isoreticular Metal-Organic Frameworks with Aromatic Pores and Dimethylammonium Cations Enable Separation of Light Hydrocarbons and Xenon/Krypton.

The separation of C2-C3 hydrocarbons from methane in natural gas and xenon/krypton purification are crucial yet challenging industrial processes. Herein, we report two isoreticular metal-organic frameworks, ZJU-89 and ZJU-90, featuring aromatic pore environments and dimethylammonium cations, that synergistically enhance the separation of these industrially relevant gas mixtures. ZJU-90 exhibits an exceptional separation performance, achieving C 3 H 8 /CH 4 and C 2 H 6 /CH 4 ideal adsorbed solution theory (IAST) selectivities of 1065 and 48, respectively, at ambient conditions, outperforming most reported adsorbent materials. Remarkably, ZJU-90 enables the recovery of >99.95% purity methane from a C 3 H 8 /C 2 H 6 /CH 4 mixture in a single adsorption step. The material also demonstrates the efficient separation of xenon from krypton, even at low concentrations. The superior performance stems from the aromatic rings decorating the pore walls and the free dimethylammonium cations in the channels, which provide an ideal chemical environment for the selective binding of C 2 H 6 , C 3 H 8 , and Xe through multiple C-H···π interactions and van der Waals forces, as elucidated by theoretical calculations. This work highlights the power of reticular chemistry in designing materials with synergistic pore environments for efficient separations.