Multilayer Graphene Sheet with Conical Nanopores as a Membrane for High-Permeance Molecular Separation

Mitigating leaks through permeable defects by stacking graphene layers would greatly reduce the molecular permeance through porous graphene membranes for gas separation. We propose a multilayer graphene membrane with conical nanopores which instead presents an ultrahigh molecular permeance even higher than those of single-layer graphene membranes. Comparison with existing experimental data also shows that such membranes present an excellent separation performance in the aspect of molecular permeance. The highly permeable conical nanopore is particularly promising for the strongly adsorbed gases on the graphene surface, such as CO2 and H2S. The underlying mechanisms are revealed by using molecular dynamics simulations, including (1) a large permeable area in the penetration side and (2) low permeation resistance caused by molecular bouncing in the nanopore for finding a possibility of permeation. The proposed conical nanopore can not only improve the molecular permeance through the defect-free and easy-fabricated multilayer graphene membranes but also provide a good example for the applications involving molecular permeation through nanopores.