Purification of octafluoropropane from hexafluoropropylene /octafluoropropane mixtures with a metal-organic framework exhibiting high productivity

Octafluoropropane (C3F8) electronic specialty gas is widely used in the process of etching and cleaning in semiconductor manufacturing industry. Removal of hexafluoropropylene (C3F6) impurities from C3F6/C3F8 mixtures thus is highly important but a formidable challenge since C3F6 and C3F8 possess similar physicochemical properties and molecular sizes. Herein we present a cobalt metal-organic framework (MOF) (termed as JXNU-21) constructed of 3-chloroisonicotinic ligands, featuring dangling 3-chloroisonicotinic ligands in the one-dimensional channels. Due to the rotation flexibility of the aromatic rings of the dangling 3-chloroisonicotinate ligands with uncoordinated nitrogen sites, the step-wise adsorption isotherms for the large-sized C3F8 were observed for JXNU-21. The high adsorption selectivity of 15.6 for C3F6/C3F8 (10:90) mixture and high C3F6 storage density (5.8 mmol g–1) under ambient conditions endow JXNU-21 with high potential for C3F6/C3F8 separation. The results of the breakthrough experiments show high-purity (99.999%) C3F8 gas can be achieved from a C3F6/C3F8 (10:90) mixture in one step. Additionally, the benchmark C3F8 productivity of 173.8 cm3 g–1 was obtained from the breakthrough experiments under ambient conditions, outperforming all other reported porous materials.