Construction of Multiple Nonpolar SF₆ Nano-Traps by Highly Stable Pyrazole-Based MOFs for SF₆ Recovery

Sulfur hexafluoride (SF₆), widely used in electric power systems, is one of the most potent greenhouse gases. Efficient separation of SF₆/N₂ by adsorptive separation technology based on porous materials is of great significance in the industry yet remains a daunting challenge. Herein, a novel strategy is introduced to construct unique pore channels with multiple SF₆ nano-traps by precisely selecting bipyrazole ligands to design the nonpolar surface of microporous metal-organic frameworks (MOFs), which significantly enhances the material's affinity for SF₆. A series of ultra-stable bipyrazole-based MOFs, M(BPZ) (M═Co, Ni, Zn), are synthesized and investigated. Among these three materials, Co(BPZ) and Zn(BPZ) show excellent SF₆ uptakes of 2.47 and 2.39 mmol g^-1 at 298 K and 0.1 bar while Co(BPZ) exhibits the highest SF₆/N₂ (10/90, v/v) IAST selectivity of 748. Breakthrough experiments reveal that SF₆/N₂ mixtures can be efficiently separated by Co(BPZ) with a high SF₆ (≥99.5 %) productivity of 46.1 L kg^-1. Theoretical calculations suggest that SF₆ preferably adsorbs in the channels through multiple S-F···π (pyrazole rings) van der Waals interactions. This work provides a straightforward approach for exploring adsorbents in efficient SF₆/N₂ separation.