Engineering Supramolecular Binding Sites in an Ultrastable and Hydrophobic Metal–Organic Framework for C2H6/C2H4 Separation

Abstract

The separation of ethane (C₂H₆) from ethylene (C₂H₄) is critical for obtaining polymer-grade C₂H₄. Adsorptive separation with C₂H₆-selective MOFs offers a viable alternative to energy-intensive cryogenic distillation, enabling the direct production of high-purity C₂H₄. In this study, we developed an ultrastable ethane-selective metal–organic framework, UiO-67-(CH₃)₂, which demonstrates enhanced C₂H₆ adsorption (4.10 mmol g^–1 at 1 bar and 298 K), higher C₂H₆/C₂H₄ selectivity of 1.70, and an increased C₂H₆/C₂H₄ adsorption ratio of 1.53 compared to unmodified UiO-67. GCMC simulations demonstrate that C₂H₆ forms more C–H···π interactions with the surrounding benzene rings and more C–H···C interactions with methyl groups compared to C₂H₄, highlighting the synergistic effects of supramolecular interactions. Furthermore, the hydrophobic pore environment also minimizes water interference, with exceptionally low water uptake (0.019 g g^–1 at 60% RH), ensuring robust separation capacity under high humid conditions. The introduction of methyl groups not only significantly enhances C₂H₆ adsorption performance and C₂H₆/C₂H₄ separation selectivity but also improves material’s hydrophobicity.