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

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.