Generating Sub-nanometer Pores in Single-Layer MoS by Heavy-Ion Bombardment for Gas Separation: A Theoretical Perspective.

Single-layer molybdenum disulfide (MoS) filters with nanometer-size pores have attracted great attention recently due to their promising performance for membrane separation. Generating nanopores in MoS controllably, however, is still a challenging task, which greatly limits the real application of MoS filters. In this work, the pore forming process in single-layer MoS by heavy-ion bombardment was investigated in detail using molecular dynamics simulations. We found that pores with sub-nanometer size (0.6-1.2 nm) can be created in the MoS sheet by single-ion bombardment, with a probability as high as 0.8 pores per incident ion. The size and shape of the nanopore can be tuned controllably by adjusting bombardment parameters. Furthermore, the performance of the MoS filter with these sub-nanometer-size pores for separation of He, Ne, H, Ar, and Kr gases was evaluated by density functional theory-based first-principles calculations. The MoS filter was found to show much higher selectivity for separating H/He and He/Ne than that reported for graphene and other membranes. Such high selectivity was attributed to the interaction between gases and the charged edge of pores in MoS. Our results suggest the potential application of ion beam technology in single-layer MoS for membrane separation.