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CO₂-philic WS₂ laminated membranes with a nanoconfined ionic liquid

Chen, Danke, Wang, Wensen, Ying, Wen, Guo, Yi, Meng, Donghui, Yan, Youguo, Yan, Rongxin, Peng, Xinsheng
Journal of materials chemistry 2018 v.6 no.34 pp. 16566-16573
carbon dioxide, energy, gases, global warming, hydrogen, ionic liquids, methane, nanosheets, nitrogen, solubility, vapor pressure, vibration
The modern global climate change and global warming of Earth make it an urgent need to develop emerging CO₂ capture and storage techniques. Herein, we first reported the use of WS₂ nanosheets to construct laminated membranes for CO₂ separation. However, the WS₂ membrane showed poor CO₂ separation performance with Knudsen selectivities for N₂/CO₂ (1.28), CH₄/CO₂ (1.72) and H₂/CO₂ (4.96). To improve the performance, an ionic liquid (IL) 1-butyl-3-methyl imidazolium tetrafluoroborate ([BMIM][BF₄]) with high CO₂ solubility and practically no vapour pressure was used for filling the nanochannels of the WS₂ membrane. Compared to the bulk IL, the nanoconfined IL exhibits higher freezing temperature, shift of vibration bands and higher interaction energy between CO₂ and ILs. Besides, the prepared WS₂ laminated membrane with the nanoconfined ionic liquid shows excellent selectivities for CO₂/N₂ (153.21), CO₂/CH₄ (68.81) and CO₂/H₂ (13.56) in single gas measurements as well as good CO₂ permeance due to the nanoconfinement of the IL. The simulation results further confirmed and explained the CO₂ separation mechanism. It indicates that the nanoconfinement of ILs into the nanochannels of two-dimensional materials is a novel way to achieve CO₂-philic membranes to efficiently separate CO₂ from other light gases.