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

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.