(674f) Ultrathin Covalent-Organic Framework Membranes for Organic Solvent Nanofiltration: A Molecular Simulation Study

Covalent-organic frameworks (COFs) are ordered crystalline materials formed by covalently linking different building blocks of light elements. Their supreme structural tunability and stability make them promising candidates for chemical separation. In this study, a series of functionalized 2D COFs are computationally designed and investigated for organic solvent nanofiltration (OSN). By grafting various functional groups onto the parent structure TpPa-1 COF, seven TpPa-X ultrathin nanofiltration membranes are produced with aperture size ranging from 5.2 Å to 7.6 Å. TpPa-X membranes show high flux towards various organic solvents, including alcohols, acetonitrile, acetone, and n-hexane. The solvent flux is mainly governed by the aperture size and functionalities of the membranes, as well as solvent properties. In general, the larger the aperture size, the higher is the flux. However, for two membranes of comparable aperture size, the hydrophobic one exhibits a higher flux towards polar solvents; while the opposite is true for non-polar solvents, where a higher flux is observed through hydrophilic membranes. The TpPa-X membranes also exhibit good rejection of active pharmaceutical ingredient (API) molecule, suggesting that they might be used for pharmaceutical applications.