Efficient SF6 Separation from a SF6/N2 Gas Mixture Based on Terephthalate Metal–Organic Framework MIL-53(Al)

Adsorptive separation presents an energy-saving and efficient separation process; however, the development of adsorbents that combine high capacity, high selectivity, and low cost remains a challenge. Here, we investigated the separation of SF₆ on three isoreticular metal–organic frameworks based on terephthalate ligands, MIL-53(Al), MIL-53(Cr), and MIL-47(V), and confirmed the promising potential of MIL-53(Al) to overcome this challenge. Compared with MIL-53(Cr) and MIL-47(V), which have larger pore sizes or lack polar μ–OH sites, MIL-53(Al) exhibited superior adsorption ability, achieving a high SF₆ uptake and SF₆/N₂ uptake ratio among the known MOFs, with low material cost. Molecular simulations revealed its strong affinity for SF₆ and guest-responsive flexibility, which was consistent with the gate-opening behavior of the isotherms. Fixed-bed breakthrough experiments confirmed the excellent performance of MIL-53(Al) in the separation of the SF₆/N₂ gas mixture, achieving the high productivity (41.50–44.88 L/kg) of 98.2–99.9% SF₆ in a single adsorption–desorption cycle at 298 K.