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 CO 2 /CH 4 and CO 2 /CO. Our investigation of the performance of three crown ether pores reveals that Pore-2 enables rapid transport of CO 2 while effectively blocking CH 4 /CO in most cases, resulting in remarkably high selectivity. In CO 2 /CH 4 mixtures, the perfect selectivity and exceptional CO 2 transport are achieved through a combination of two gases size difference and robust trapping of CO 2 by Pore-2. For CO 2 /CO mixtures, the subtle difference in electrostatic interaction between Pore-2 and the two gases, with the carbon in CO 2 possessing a higher positive charge than that in CO, is responsible for the selective separation of CO 2 /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 CO 2 /CH 4 and CO 2 /CO separation, suggesting their potential as advanced gas sieving membranes.