The separation of xenon/krypton (Xe/Kr) mixtures plays a vital role in the industrial process of manufacturing high-purity xenon. Compared with energy-intensive cryogenic distillation, porous materials based on physical adsorption are very promising in the low-cost and energy-saving separation processes. Herein, we show that a cationic metal-organic framework (named as FJU-55) exhibits highly efficient Xe/Kr separation performance, which can be attributable to its uniform three-dimensional (3D) interconnection channels and the electro-positive features as the host framework. Moreover, FJU-55 demonstrates good Xe adsorption capacity of 1.41 mmol/g and excellent Xe/Kr selectivity of 10 (298 K and 100 kPa), together with a high Q_st value of 39.4 kJ/mol at low coverage area. The superior Xe/Kr separation performance of FJU-55 was further confirmed by the dynamic breakthrough experiments. Results obtained via molecular modeling studies have revealed that the suitable pore size and abundant accessible aromatic ligands in FJU-55 could offer strong multiple C–H∙∙∙Xe interactions, which play a collaborative role in this challenging gas separation task.

The separation of light hydrocarbons, including C₂H₆ and C₃H₈, is essential to natural gas upgrading. Meanwhile, N₂ removal from CH₄ is also crucial to concentrating low-quality coalbed methane, but the adsorption process is challenging because of the close kinetic diameter. This work reports two hydrogen-bonded metal-nucleobase frameworks (HOF-ZJU-201 and HOF-ZJU-202) capable of efficiently separating C₃H₈/CH₄, C₂H₆/CH₄, and CH₄/N₂. Due to strong affinity for C₃H₈ and C₂H₆, the low-pressure capacity for C₃H₈ (5 kPa) and C₂H₆ (10 kPa) of HOF-ZJU-201a exceeds most adsorbents. The ideal adsorbed solution theory (IAST) selectivity of C₃H₈/CH₄ and C₂H₆/CH₄ is 119 and 45 at ambient conditions. According to density functional theory calculations, surface polarization environments formed by electron-rich anions and electron-deficient purine heterocyclic rings contribute to the selective capture of C₃H₈ and C₂H₆ with greater polarizability. Furthermore, the high CH₄ adsorption capacity (1.73 mmol/g for HOF-ZJU-201a and 1.50 mmol/g for HOF-ZJU-202a at 298 K and 1.0 bar) and excellent CH₄/N₂ selectivity (6.0 for HOF-ZJU-201 at 298 K), as well as dynamic breakthrough experiments of binary CH₄/N₂ gas mixture implied their efficacy in the concentration of low-quality coalbed methane.