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 impurities in the end product, even with state-of-the-art separation membranes. In this study, we demonstrate, using a molecular dynamics simulation approach, that graphene membranes embedded with crown ether nanopores exhibit unprecedented separation efficiency for CO2/CH4 and CO2/CO. Our investigation of the performance of three crown ether pores reveals that Pore-2 enables rapid transport of CO2 while effectively blocking CH4/CO in most cases, resulting in remarkably high selectivity. In CO2/CH4 mixtures, the perfect selectivity and exceptional CO2 transport are achieved through a combination of two gases size difference and robust trapping of CO2 by Pore-2. For CO2/CO mixtures, the subtle difference in electrostatic interaction between Pore-2 and the two gases, with the carbon in CO2 possessing a higher positive charge than that in CO, is responsible for the selective separation of CO2/CO. The separation capacity of Pore-2 under different gas feed ratios and temperatures undergoes a slight performance reduction in some cases. Our findings highlight the superior performance of graphene crown ether nanopores for CO2/CH4 and CO2/CO separation, suggesting their potential as advanced gas sieving membranes.