Highly Efficient CO₂/C₂H₂ Separation by Porous Graphene via Quadrupole Gating Mechanism

Abstract

Acetylene (C2H2) is an important and widely used raw material in various industries (such as petrochemical). Generally, a product yield is proportional to the purity of C2H2; however, C2H2 from a typical industrial gas-production process is commonly contaminated by CO2. So far, the achievement of high-purity C2H2 separated from a CO2/C2H2 mixture is still challenging due to their very close molecular dimensions and boiling temperatures. Taking advantage of their quadrupoles with opposite signs, here, we show that the graphene membrane embedded with crown ether nanopores can achieve an unprecedented separation efficiency of CO2/C2H2. Combining the molecular dynamics simulation and the density functional theory (DFT) approaches, we discovered that the electrostatic gas-pore interaction favorably allows the fast transport of CO2 through crown ether nanopores while completely prohibiting C2H2 transport, which yields a remarkable permeation selectivity. In particular, the utilized crown ether pore is capable of allowing the individual transport of CO2 while completely rejecting the passage of C2H2, independent of the applied pressures, fed gases ratios, and exerted temperatures, featuring the superiority and robustness of the crown pore in CO2/C2H2 separation. Further, DFT and PMF calculations demonstrate that the transport of CO2 through the crown pore is energetically more favorable than the transport of C2H2. Our findings reveal the potential application of graphene crown pore for CO2 separation with outstanding performance.