Optimization of interlayer spacing and pore structure in multilayer graphene oxide membranes via pressure-driven molecular dynamics simulations

The interplay between interlayer spacing ( H ) and pore width ( A ) plays a central role in determining the performance of graphene oxide (GO) membranes for water desalination. In this work, atomistic molecular dynamics simulations employing the OPLS-AA force field and the TIP3P water model are used to investigate pressure-driven water and ion transport through multilayer porous GO membranes. Unlike previous studies, the effects of H and A are systematically decoupled by maintaining a constant pore offset, enabling geometric confinement to be isolated from tortuosity effects. The results show that interlayer spacings near H ≈ 11.0 Å exhibit enhanced mechanical stability under high applied pressure due to the formation of robust hydration layering, which suppresses the structural collapse observed in more confined channels. Transport analysis reveals the emergence of a high-flux plateau regime in which variations in hydraulic permeability become statistically marginal across multiple geometries. Within this regime, configurations combining restricted pore entrances with moderately expanded interlayer spacing provide a favorable balance between water transport and structural robustness. Although no ion permeation events are observed within the simulation window, pronounced differences in internal ion dynamics are identified. Wider pore architectures promote increased intra-membrane ion accumulation, whereas restricted pore designs effectively limit internal ion retention by enforcing steric exclusion at the feed interface. Overall, these findings establish a design framework for GO membranes that shifts optimization from maximizing flux alone toward controlling intra-channel ion accumulation to enhance long-term operational stability.