Efficient SF6 capture and separation in robust gallium- and vanadium-based metal–organic frameworks

Abstract

Sulfur hexafluoride (SF₆) is a highly potent greenhouse gas (GHG) that is mainly emitted from high-voltage electrical applications. The global warming potential (GWP) of the gas is almost 23 000 times that of CO₂ and therefore, controlling its emission and recovery is of great importance from both an environmental and economic perspective. Solid adsorbents and adsorption-based technology is a cost-effective and energy-efficient pathway to recapture SF₆ from its sources, which usually consist of dilute SF₆ in N₂. Here, we present a group of four highly porous and robust gallium- or vanadium-based metal–organic frameworks (MOFs) with exceptional SF₆ uptake and selectivity. In particular, the novel gallium 1,2,4,5-tetrakis(4-carboxlatephenyl)benzene (TCPB⁴⁻) MOF (Ga-TBAPy) possesses 1-dimensional channels of suitable size (5.2 × 8.4 Å and 5.3 × 10 Å) to adsorb up to 2.25 mmol g⁻¹ of SF₆ at 10 kPa with an excellent SF₆-over-N₂ selectivity of 418. Ga-TCPB also exhibits high chemical stability in aqueous and acidic media as well as in organic solvents. 3D electron diffraction (3D ED) patterns combined with high-resolution electron microscopy images were employed to investigate the structure of these water-stable and cyclable MOF SF₆ adsorbents. Furthermore, this study demonstrates the possibility of using these highly stable MOFs to capture SF₆ from a gas mixture as well as how MOFs can offer an alternative and efficient way to mitigate the global warming contributions from the emission of SF_6.