A nickel-based metal-organic framework for efficient SF6/N2 separation with record SF6 uptake and SF6/N2 selectivity

Seeking top-performing adsorbents with salient structural stability and renewability to realize efficient adsorption and enrichment of sulfur hexafluoride (SF6) from the gaseous blend is of great importance. Here, an ultramicroporous nickel-based metal-organic framework (MOF), termed Ni(NDC)(TED)0.5 with multiple naphthalene rings-functionalized pore environment, was synthesized to efficiently separate SF6/N2 mixture. Equilibrium adsorption results show that Ni(NDC)(TED)0.5 possesses a record IAST SF6/N2 selectivity (7 5 0) and SF6 uptake (61.86 cm3 cm−3), higher than all adsorbents reported so far, and resolves the trade-off phenomenon between SF6 adsorption capacity and SF6/N2 selectivity. In particular, the selectivity is 2.3 times that of the current highest material (SBMOF-1). Furthermore, theoretical calculations reveal that the pore centers of material are the most energetically-favorable preferential adsorption sites. Meanwhile, the stronger affinity between SF6 and framework is attributed to the shorter interaction distance between F atom on SF6 and pore wall. Breakthrough tests confirm this MOF can completely separate SF6/N2 mixture. The breakthrough uptake (56.60 cm3 cm−3) and dimensionless time (τ: 281.8) of this material for SF6 are separately 1.6 and 2.5 times that of the currently reported benchmark (Cu-MOF-NH2). In combination of excellent structural stability and recyclability, this material may be an ideal material for the recovery of SF6 from SF6/N2 mixture.