Molecular dynamics screening of water desalination through a graphdiyne–Ti3C2F2 Janus-type bilayer membrane: Observed salt rejection and water permeation under accelerated conditions

Nour El Haq El Macouti, Mohamed El Bouanounou, Abdelmajid Assila, E.K. Hlil, Y. Boughaleb, Mouhaydine Tlemçani, Abdеlowahеd Hajjaji, Said Laasri

Classical molecular dynamics simulations were used as a preliminary mechanistic screening tool to examine water desalination through an asymmetric graphdiyne–Ti 3 C 2 F 2 Janus-type bilayer membrane. A single 10 ns trajectory was performed at 300 K using a 0.6 M NaCl feed solution and an accelerated driving pressure of 150 MPa. Under these conditions, 141 water molecules crossed the membrane after the initial wetting period, corresponding to an observed permeation rate of approximately 14 molecules/ns, or 1876 mol m -2 s -1 at the simulated pressure. No Na + ions and one Cl − ion crossed the membrane, giving finite-trajectory rejection values of 100% and 95.5%, respectively. Because these values come from one trajectory and one Cl − event, they are not statistically converged membrane constants. Density profiles, RDFs, hydrogen-bond analysis, an apparent density-derived free-energy profile, pore stability, and water-orientation analysis suggest that ion exclusion is associated with dehydration at the enlarged pore and asymmetric membrane–water interactions. Quantitative validation requires independent replicas, graphdiyne-only controls, pressure-dependent simulations, and equilibrium free-energy calculations.