Generating Sub-nanometer Pores in Single-Layer MoS₂ by Heavy-Ion Bombardment for Gas Separation: A Theoretical Perspective

Single-layer molybdenum disulfide (MoS₂) filters with nanometer-size pores have attracted great attention recently due to their promising performance for membrane separation. Generating nanopores in MoS₂ controllably, however, is still a challenging task, which greatly limits the real application of MoS₂ filters. In this work, the pore forming process in single-layer MoS₂ 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 MoS₂ 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 MoS₂ filter with these sub-nanometer-size pores for separation of He, Ne, H₂, Ar, and Kr gases was evaluated by density functional theory-based first-principles calculations. The MoS₂ filter was found to show much higher selectivity for separating H₂/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 MoS₂. Our results suggest the potential application of ion beam technology in single-layer MoS₂ for membrane separation.