(130d) Ab Initio Force Field for Functional Groups on MoS2 Nanopores: Effects on Water Permeability and Ion Rejection

Ultrathin nanoporous membranes composed of two-dimensional (2D) materials exhibit exceptional properties, including high specific surface areas and superior separation efficiency, making them promising candidates for water treatment applications. Among these materials, molybdenum disulfide (MoS₂) stands out due to its remarkable long-term stability and excellent desalination performance compared to other 2D materials. While recent studies have demonstrated the potential of MoS₂ as membranes for desalination, previous molecular dynamics (MD) simulations have predominantly considered unfunctionalized Mo and S atoms at nanopore edges.^1,2 This limitation arises from the current lack of classical force fields capable of accurately describing functionalized MoS₂ nanopores, where interactions between water molecules and edge atoms may lead to the possibility of functionalization with hydrogen (H) and hydroxyl (OH) groups. To address this gap, we employ density functional theory (DFT)-based ab initio molecular dynamics (AIMD) simulations to investigate MoS₂ nanopores in an aqueous environment, where both Mo and S edges are exposed to water molecules. Our results reveal a strong tendency for hydrogenation at S sites and hydroxylation at Mo sites, suggesting a viable approach for tuning membrane properties. Utilizing potential energy surfaces (PES) obtained from DFT calculations, we develop high-fidelity force fields for H- and OH- functionalized MoS₂ nanopores. The resulting force field enables stable MD simulations of water and ion transport through Mo-OH and S-H terminated nanopores. In light of our proposed force field, previous simulation results through unfunctionalized MoS₂ nanopores would have to be re-evaluated. Overall, this work provides a framework for the realistic modeling of edge-functionalized MoS₂ in aqueous environments, facilitating its exploration for various applications in water purification, separation technologies, DNA sequencing, and a wide range of other fields.

References

(1) Hoenig, E.; Han, Y.; Xu, K.; Li, J.; Wang, M.; Liu, C. In Situ Generation of (Sub) Nanometer Pores in MoS₂ Membranes for Ion-Selective Transport. Nat Commun 2024, 15 (1), 7911. https://doi.org/10.1038/s41467-024-52109-8.

(2) Heiranian, M.; Farimani, A. B.; Aluru, N. R. Water Desalination with a Single-Layer MoS₂ Nanopore. Nature Communications 2015, 6 (1), 8616. https://doi.org/10.1038/ncomms9616.