Engineering nano-trap distribution in metal-organic frameworks enables boost of SF₆/N₂ separation

Separating/capturing SF₆, having the strongest global warming potential, from exhaust gas with low concentration (1%–10%) in the power industry is significant for both greenhouse gas emission control and SF₆ recycling and reutilization. In this study, we achieved highly efficient SF₆/N₂ separation under different SF₆ concentrations (1% and 10%) using two homologous metal-organic frameworks, Ni-bpz and Zn-bpz. This outcome underscores the effectiveness of rational nano-traps distribution engineering for targeted separation applications. The molecular simulation suggests that an SF₆ molecule interacts with a single nano-trap in Zn-bpz. At the same time, it is efficiently confined by two adjacent nano-traps in the parallel distribution of Ni-bpz. Consequently, exceptional SF₆/N₂ selectivity for 1/99 and 10/90 mixtures have been respectively achieved in Ni-bpz (516, SF₆/N₂ = 1/99) and Zn-bpz (608, SF₆/N₂ = 10/90) at 298 K and 1 bar. In dynamic breakthrough experiments, Ni-bpz exhibits a record pure N₂ (≥ 99.99%) productivity (1496 mL/g) for an SF₆/N₂ (1/99) gas mixture. Moreover, both MOFs demonstrate excellent water resistance across multiple cycles, suggesting their high promise for practical application.