Highly-selective MOF-303 membrane for alcohol dehydration

• Published in: Journal of membrane science Vol. 661; p. 120879
• Main Authors: Lai, Jun-Yu, Wang, Ting-Yuan, Zou, Changlong, Chen, Jiun-Jen, Lin, Li-Chiang, Kang, Dun-Yen
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05-11-2022
• Subjects: Alcohol dehydration; Metal-organic framework; MOF membrane; Pervaporation; Metal-organic framework; MOF membrane; Alcohol dehydration; Pervaporation
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2022.120879

Metal-organic frameworks (MOFs) are an emerging class of crystalline microporous materials, which have drawn considerable attention for separation applications. While a number of successful examples of MOF-based membranes for gas separation have been reported, only a few of pure MOF membranes presented high performance in pervaporation. This work reports on the application of a highly hydrophilic MOF, MOF-303, for dehydration of ethanol as well as isopropanol (IPA) via pervaporation. Dense MOF-303 membranes are fabricated with either a sodium hydroxide or urea solution. The latter recipe renders MOF-303 crystals a low quantity of missing linker; and it also yields a membrane with fewer pinhole-type defects. The MOF-303 membrane prepared with urea presents a relatively low air permeance and much higher separation performance for of water-ethanol and water-IPA mixtures, as compared to that synthesized with sodium hydroxide. The MOF-303-urea membrane possesses high separation factors for water/ethanol (55349) and for water/IPA (3801) at 303 K. At a higher temperature of 343 K, this membrane still offers a good water/ethanol separation factor of 1874. A 7-day pervaporation operation on the MOF-303-urea membrane demonstrates that the separation performance drops gradually during the test, but it can be restored via a thermal treatment on the membrane. Molecular simulations are performed to shed light on the transport property of water, ethanol, and IPA in MOF-303. The computational results suggest that the dehydration capability of this MOF can be attributed to both of its water-selective adsorption and diffusion, particularly the latter. Specifically, a relatively high diffusion barrier to the alcohols in MOF-303 results in the high selectivity of water over ethanol or IPA.
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•MOF-303 membrane presents water/ethanol selectivity of nearly 60,000.•The separation performance of MOF-303 membrane can be restored through thermal reactivation.•Molecular simulations elaborate key structural characteristics of MOF-303 for its high water/alcohol selectivity.