Novel Carborane Based Metal Organic Framework for Record Electronic Specialty Gas C2F6 Purification via Molecular Sieving.

The production of high-purity perfluoroethane (C2F6), an essential electronic specialty gas, requires the removal of its partially-fluorinated analog, pentafluoroethane C2F5H. This separation is exceptionally challenging due to their similar physicochemical properties. Herein, we report a novel carborane-based metal-organic framework, ZNU-23 (Ni-CB-HPBTA), engineered with a pearl-chain-like pore architecture to achieve unprecedented molecular sieving separation. The narrow pore channel and large cavity in ZNU-23 facilitate the high and fast uptake of C2F5H (65.2 cm3·g-1 at 298 K and 1 bar) while nearly completely excluding C2F6, leading to a record-high IAST selectivity exceeding 5000 for a C2F5H/C2F6 (1/99) mixture. Dynamic breakthrough experiments confirm its excellent separation performance across various mixture ratios, remarkable stability under humid and elevated-temperature conditions, and superb recyclability. Mechanistic studies via GCMC simulations and DFT calculations attribute this performance to the multi-site confinement of C2F5H within the pearl-chain pores and the complete steric exclusion of the larger C2F6 molecule. The potential C2F5H binding sites within the framework were further revealed by C2F5H-loaded single crystal structure of ZNU-23.