Highly efficient and selective H2/CH4 separation by graphene membranes with embedded crown ethers

Designing a highly selective and fast separation membrane is critical to realize H2-sieving with efficient performance, which is still a challenge by far. In this study, we combine molecular dynamics (MD) and first-principle approaches to investigate the H2 separation property of graphene crown ether. Our MD results demonstrate that graphene crown ether exhibits a superior H2-sieving performance under various temperatures and external pressures, allowing fast passage for H2 while completely rejecting CH4. The H2 permeability exceeds 105 GPU at selectivities exceeding 1500. These results highlight an outstanding performance of crown ether pores for separating H2 from mixtures with CH4. Observed from MD simulation trajectories, this highly selective separation is caused by the intrinsic dimensional difference between the two types of gases and the pore. The first-principle calculations further confirm that it is energetically more favorable for H2 to transit the graphene crown ether than for CH4. Our findings suggest a novel application of the graphene crown ether in H2-sieving with great promise for future membrane designs.