Recovery of High-Purity SF from Humid SF/N Mixture within a Co(II)-Pyrazolate Framework.

Sulfur hexafluoride (SF) is extensively employed in the power industry. However, its emissions significantly contribute to the greenhouse effect. The direct recovery of high purity SF from industrial waste gases would benefit its sustainable use, yet this represents a considerable challenge. Herein, we report the enrichment of SF from SF/N mixtures via adsorptive separation in a stable Co(II)-pyrazolate MOF BUT-53 (BUT: Beijing University of Technology), which features dynamic molecular traps. BUT-53 exhibits an excellent SF adsorption uptake of 2.82 mmol/g at 0.1 bar and 298 K, as well as an unprecedented SF/N (10:90) selectivity of 2485. Besides, the remarkable SF/N selectivity of BUT-53 enables recovery of high purity (>99.9%) SF from a low concentration (10%) mixture through a breakthrough experiment. The excellent SF/N separation efficiency was also well maintained under humid conditions (RH = 90%) over multiple cycles. Molecular simulation, single-crystal diffraction, and adsorption kinetics studies elucidate the associated adsorption mechanism and water tolerance.