Self-assembled topological structures of post-processed two-dimensional materials exhibit novel physical properties distinct from those of their parent materials. Herein, the critical role of desulphurization on self-assembled topological morphologies of molybdenum disulfide ($MoS_2$) monolayer sheets is explored using molecular dynamics (MD) simulations. MD results show that there are differences in atomic energetics of $MoS_2$ monolayer sheets with different desulphurization contents. Both free-standing and substrate-hosted $MoS_2$ monolayer sheets show diversity in topological structures such as flat surface, wrinkles, folds and scrolls, depending on the desulphurization contents, planar dimensions and ratios of length-to-width of $MoS_2$ monolayer sheets. Particularly, at the critical desulphurization contents, they roll up into nanotube morphology, consistent with previous experimental observations. Moreover, the observed differences in the molecular morphological diagrams between free-standing and substrate-hosted $MoS_2$ monolayer sheets can be attributed to unique interatomic interactions and van der Waals interactions in them. The study provides important insights into functionalizing structural morphological properties of two-dimensional materials, e.g., $MoS_2$, via defect engineering.
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