Divergent Adsorption Regulation in Metal-Organic Frameworks for Highly Efficient CF/CF Separation.

The efficient removal of low-concentration components from homologous mixtures is often hampered by the co-directional effect of traditional thermodynamic regulation approaches, typically leading to a trade-off between adsorption capacity and selectivity. Focusing this challenge on the critical task of purifying perfluorocarbons in electronics industry, a divergent regulation strategy is reported that significantly improves the separation efficiency of low-concentration hexafluoroethane (CF) from tetrafluoromethane (CF). This approach involves the selective shielding of open metal sites and the modulation of channel geometry within an electron-deficient ligand-based pore environment, thereby facilitating a CF dense-packing accommodation mode while weakening the CF affinity due to the reduced host-guest interactions. Simultaneously enhanced CF adsorption and reduced CF adsorption are achieved, resulting in record-high low-pressure CF uptake and CF/CF selectivity. Comprehensive insights into the unique separation mechanism are illustrated through a combination of solid-state MAS nuclear magnetic resonance (SSNMR), molecular simulations, and meticulously designed comparative experiments. As a result, benchmark CF/CF separation performance is achieved, as demonstrated by the unprecedented electronic-grade (over 99.999%) CF productivity (401 L kg) obtained from an industrially relevant CF/CF (3:97) mixture, as well as the excellent water/air/heat stability and recyclability.