A novel hydrophobic carborane-hybrid microporous material for reversed C2H6 adsorption and efficient C2H4/C2H6 separation under humid conditions

Abstract

Since ethylene (C₂H₄) is important feedstock in the chemical industry, developing economical and energy-efficient adsorption separation techniques based on ethane (C₂H₆)-selective adsorbents to replace the energy-intensive cryogenic distillation is highly demanded, which however remains a daunting challenge. While previous anionic boron cluster hybrid microporous materials display C₂H₄-selective features, we herein reported that the incorporation of a neutral para-carborane backbone and aliphatic 1,4-diazabicyclo[2.2.2]octane (DABCO) enables the reversed adsorption of C₂H₆ over C₂H₄. The generated carborane-hybrid microporous material ZNU-10 (ZNU = Zhejiang Normal University) is highly stable in humid air and maintains good C₂H₆/C₂H₄ separation performance under high humidity. Gas loaded single crystal structure and density-functional theory (DFT) calculations revealed that the weakly polarized carborane and DABCO within ZNU-10 induce more specific C–H^δ+⋯H^δ−–B dihydrogen bonds and other van der Waals interactions with C₂H₆, while the suitable pore space allows the high C₂H₆ uptake. Approximately 14.5 L kg⁻¹ of polymer grade C₂H₄ can be produced from simulated C₂H₆/C₂H₄ (v/v 10/90) mixtures under ambient conditions in a single step, comparable to those of many popular materials.