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

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