Defective MOF incorporating CF3 functionality via fragmented linker co-assembly for high C2H6/C2H4 selectivity and C2H6 uptake

The production of high-purity ethylene requires an adsorbent with high C₂H₆/C₂H₄ selectivity, outstanding C₂H₆ adsorption, and facile C₂H₆ regeneration. Towards this goal, a series of novel defective CF₃-functionalized metal–organic framework (MOF) materials (UiO-66-nCF₃, n = 25, 50, 60, and 75) were synthesized by co-assembling the framework with terephthalic acid as the linker and various percentages (n) of CF₃-functionalized ligands. The C₂H₆ adsorption strength increased as the density of CF₃ groups increased. In particular, UiO-66-50CF₃ exhibited high C₂H₆/C₂H₄ selectivity (2.04), excellent C₂H₆ adsorption (2.5 mmol/g), and modest C₂H₆ isosteric heat of adsorption (Q_st) (∼28.9 kJ/mol). Additionally, the material exhibited high C₂H₆/C₂H₄ breakthrough selectivity (1.64) and large high-purity (>99.9 %) C₂H₄ productivity (7.32 L_STP kg⁻¹) under dynamic flow conditions (C₂H₆/C₂H₄ = 1:15 (v/v)). UiO-66-50CF₃ could readily be regenerated at room temperature, and demonstrated good hydrothermal stability in boiling water for 1 h and high thermal stability up to 500 °C. The incorporation of a high density of CF₃ groups within a MOF via fragmented linker co-assembly is a promising strategy for developing adsorbents for C₂H₆/C₂H₄ separation.