Efficient SF<sub>6</sub> 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 N-2. 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 x 8.4 & Aring; and 5.3 x 10 & Aring;) to adsorb up to 2.25 mmol g(-1) of SF6 at 10 kPa with an excellent SF6-over-N-2 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 SF6.