Molecular dynamics decoding of solvent polarity effects in two-dimensional MoSe2 membrane for organic solvent nanofiltration

Two-dimensional (2D) MoSe 2 is a promising candidate for organic solvent nanofiltration (OSN) membranes. Decoding its intrinsic OSN mechanism, particularly the regulatory role of solvent polarity, is essential for advancing its applications. In this study, all-atom molecular dynamics simulations are utilized to systematically explore the OSN mechanism of 2D MoSe 2 membranes. The results indicate that the permeabilities of all tested solvents increase monotonically with the enlargement of the interlayer spacing ( d ) in MoSe 2 membranes. For nonpolar solvents, the permeabilities are hardly affected by the interfacial effect of MoSe 2 nanosheets, with an exception only observed at d = 0.90 nm where benzene molecules form a upright arrangement inside the membrane due to their strong π-π interactions, which thereby inhibits the transport. For polar solvents, the permeabilities are significantly dominated by the interfacial effect of MoSe 2 nanosheets when d ≤ 1.45 nm. As the d increases beyond 2.00 nm, the influence of interfacial effect gradually weakens. However, acetonitrile remains a layered arrangement even at d = 2.50 nm due to its strong interaction with the MoSe 2 membrane. The rejection of α-methylstyrene dimer decreases with increasing d , and enhancing the polarity of solvents could effectively elevate its rejection rate. This work provides essential insights into the OSN mechanism of 2D MoSe 2 membranes, which is of great significance for the development of 2D-based OSN membranes. • All-atom MD simulations decode solvent transport in 2D MoSe 2 membranes. • Solvent permeability increases monotonically with interlayer spacing ( d ). • Nonpolar solvent transport is weakly affected by solvent-membrane interactions. • Polar solvent permeability is strongly governed by MoSe 2 interfacial effects. • α-Methylstyrene dimer rejection decreases with d but rises with solvent polarity.