Crown Ether Nanopores in Graphene Membranes for Highly Efficient CO2/CH4 and CO2/CO Separation: A Theoretical Study

Gas separation is a critical step in various applications,e.g.,industrial separation and purification and carbon capture and separation,although it remains challenging due to the presence of impuritiesin the end product, even with state-of-the-art separation membranes.In this study, we demonstrate, using a molecular dynamics simulationapproach, that graphene membranes embedded with crown ether nanoporesexhibit unprecedented separation efficiency for CO2/CH4 and CO2/CO. Our investigation of the performanceof three crown ether pores reveals that Pore-2 enables rapid transportof CO2 while effectively blocking CH4/CO inmost cases, resulting in remarkably high selectivity. In CO2/CH4 mixtures, the perfect selectivity and exceptionalCO(2) transport are achieved through a combination of twogases size difference and robust trapping of CO2 by Pore-2.For CO2/CO mixtures, the subtle difference in electrostaticinteraction between Pore-2 and the two gases, with the carbon in CO2 possessing a higher positive charge than that in CO, is responsiblefor the selective separation of CO2/CO. The separationcapacity of Pore-2 under different gas feed ratios and temperaturesundergoes a slight performance reduction in some cases. Our findingshighlight the superior performance of graphene crown ether nanoporesfor CO2/CH4 and CO2/CO separation,suggesting their potential as advanced gas sieving membranes.