Electrostatic Potential Matching in an Anion-Pillared Framework for Benchmark Hexafluoroethane Purification from Ternary Mixture

Abstract

One-step purification of CF₃CF₃ from ternary CF₃CH₂F/CF₃CHF₂/CF₃CF₃ mixture is crucial since its vital role in the semiconductor industry. However, efficient separation of chemically inert CF₃CF₃ remains challenging due to the difficulty in creating specific recognition sites in porous materials. In this work, we report the first example of anion-pillared MOFs to the separation of fluorinated electronic specialty gases, utilizing the unique electrostatic potential matching in the bipolar pores of SIFSIX-1-Cu to realize a benchmark CF₃CH₂F/CF₃CHF₂/CF₃CF₃ separation. SIFSIX-1-Cu exhibits the highest CF₃CH₂F and CF₃CHF₂ adsorption capacity at 0.01 bar, as well as the highest CF₃CH₂F/CF₃CF₃ and CF₃CHF₂/CF₃CF₃ IAST selectivity. Additionally, high-purity (≥ 99.995%) CF₃CF₃ with record productivity (882.9 L kg⁻¹) can be acquired through one-step breakthrough experiment of CF₃CH₂F/CF₃CHF₂/CF₃CF₃ (5/5/90). Theoretical calculations further reveal that the coexistence of electronegative SiF₆²⁻ and partially electropositive H sites promotes SIFSIX-1-Cu to effectively anchor CF₃CH₂F and CF₃CHF₂ through multiple supramolecular interactions.