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.