Organic solvent permeation through HKUST-1 MOF membranes: Molecular-scale insights

HKUST-1 is a popular metal-organic framework (MOF) that is widely for organic solvent nanofiltration (OSN). This study targets a molecular-level understanding of the organic solvent permeation characteristics of HKUST-1-based OSN membranes. Non-equilibrium molecular dynamics (NEMD) simulations are conducted to investigate the permeation of two polar (namely, methanol and acetone) and five non-polar (namely, hexane, cyclohexane, toluene, xylene, and CCl 4 ) organic solvents through the HKUST-1 membrane. Compared to polar protic methanol and polar aprotic acetone, non-polar solvents exhibited higher solvent flux due to their weaker interactions with the HKUST-1 membrane, except for CCl 4 , which has the highest viscosity and relatively larger molecular diameter. Among the non-polar solvents, the highest permeation flux exhibited by hexane (256×10 4 ± 24×10 4 kg∙m -2 ∙h -1 ) is attributable to the lowest viscosity, narrow potential mean force distribution, relatively lower energy barrier, and loss of long-range interactions. Furthermore, it is recommended to use the moving wall (MW)-NEMD approach for slow-permeating solvents, owing to its straightforward implementation and ease of use. Conversely, the boundary-driven (BD)-NEMD method is more effective for fast-permeating solvents, as it allows for extended simulation times with reasonably sized systems, avoiding the need for large-scale setups and thereby reducing computational costs. The molecular-level insights revealed here are expected to be valuable in the advancement of MOF membranes for OSN. • Molecular dynamics study of organic solvent permeation through the HKUST-1 MOF • Compared permeation of two polar and five non-polar organic solvents • Non-polar solvents permeate faster due to weaker interactions with membrane • Highest flux is tied to low viscosity, narrow PMF distribution, low energy barrier • Different NEMD approaches recommended depending on permeation rates