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From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
Liquid-Liquid Phase Separation of Aqueous Ionic Liquids in Covalent Organic Frameworks for Thermal Switchable Proton
Wenhui Yao1, Yongkui Chen1,2, Timing Fang3
1School of Chemistry and Materials Engineering, Xinxiang University, Xinxiang, Henan 453003, P. R. China.
Abstract:
Covalent organic frameworks (COFs) have regular channels that can accommodate guest molecules to provide highly conductive solid electrolytes. However, designing smart, conductive COFs remains a great challenge. Herein, we report the first example of PEG-functionalized ionic liquids (ILs) anchored on the COF walls by strong hydrogen bonding to fabricate thermally responsive COFs (IL@COF). We found that similar to the traditional IL/water mixture, the ILs undergo lower critical solution temperature (LCST)-type phase behavior within COF nanopores under high moisture levels. However, the phase separation temperature of aqueous IL decreases in COF channels due to the strong interaction between the IL and COF. Thus, the proton conductivity of IL@COF can be reversibly switched by phase miscibility and separation in COF nanopores, and there is no obvious decrease even after 20 switching cycles. Our work provides important clues for understanding liquid-liquid phase separation in a confined nanospace and opens a new pathway to switchable proton conductivity.
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