CO2-philic WS2 laminated membranes with a nanoconfined ionic liquid

Abstract

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.