Integrated High Water Affinity and Size Exclusion Effect on Robust Cu-Based Metal–Organic Framework for Efficient Ethanol–Water Separation

Purification of ethanol from ethanol/water mixtures is important in industrial separation processes, especially for bioethanol fuel purification. In this work, a robust Cu-triazole metal–organic framework (Cu-Tria) with interconnected 3D supermicroporous channels containing tridentate bridging triazole ligands and rich open Cu2+ sites was identified to separate ethanol/water mixtures. By virtue of the size exclusion effect for ethanol and excellent water affinity, this MOF exhibits an ideal molecular sieving effect for ethanol/water separation. The DFT calculation results reveal that a water molecule can form coordination bonds with Cu2+ open metal sites, and the subsequent water molecules can form multiple hydrogen bonds with the coordinated water. Breakthrough experiments of water/ethanol mixtures (v/v = 5/95) show that complete water/ethanol separation can be achieved, and online mass spectrometry results reveal that the purity of the collected ethanol from the outlet is up to 99.99%. More importantly, this MOF displays excellent water, alkali, and acid stability, as well as outstanding recyclability for water/ethanol separation. Consequently, the Cu-Tria can be deemed as a potential porous adsorbent for the purification of bioethanol fuel.