Molecular insights into the CO2 separation mechanism of GO supported deep eutectic solvent membrane

[Display omitted] •The GO-SDESMs show excellent CO2 selectivity over N2 and gas permeability.•MD combined with DFT simulations are used to study the CO2 separation mechanism.•Changing the ChCl/EG molar ratio can feasibly modulat the gas separation capacity. The two-dimensional material supported ionic liquid membrane has been proved to have good stability and CO2 separation performance. However, the high price of ionic liquid largely limits its practical utilization. On benefit of the low price and good CO2 separation performance, the deep eutectic solvent (DES) has significant advantage for practical application comparable to current popular polymer gas separation membrane. However, as one new members of gas separation membrane, the CO2 separation mechanism of two-dimensional material supported deep eutectic solvent membrane is still unclear. In this work, the graphene oxide supported deep eutectic solvent (ChCl/EG) membrane (GO-SDESM) were prepared, and molecular dynamics simulation combined with density functional theory were adopted to investigate the CO2 separation performance. The higher DES/CO2 interaction than that of DES/N2 provides excellent CO2 solubility selectivity over N2. Moreover, it was found that the separation performance could be feasibly modulated by changing the ChCl/EG molar ratio. With the decreased proportion of ChCl in DES, both the CO2 permeance and N2 permeance increases, and the CO2 selectivity keeps perfect 100% at low ChCl/EG molar ratio and decreases at high ChCl/EG molar ratio. The modulation mechanisms were discussed in detail from the driving force and resistance force of gas transmembrane transport, viscosity and free volume of DES. Our study provides a molecular level understanding of the gas separation mechanism of GO-SDESM and provides theoretical guidance for the design of gas separation membranes.