Effects of functionalization on the nanofiltration performance of PIM-1: Molecular simulation investigation

As a unique class of microporous polymers, polymers of intrinsic microporosity (PIMs) have attracted considerable interest for organic solvent nanofiltration (OSN). Here, we report a molecular simulation study to investigate OSN through six PIMs (pristine PIM-1 and five functional PIMs). The permeabilities of four organic solvents (methanol, ethanol, acetonitrile and acetone) through PIM-1 are found to correlate well with a combination of membrane and solvent properties. In the presence of a solute (mometasone furoate), the predicted solvent permeabilities through PIM-1 agree well with available experimental data. The solute is 100% rejected in all the solvents; however, it has different effects on solvent permeation. For protic solvents (methanol and ethanol), the permeabilities are marginally reduced by the solute; this is attributed to the favourable interaction between the solute and protic solvent, thus the solute is less accumulated at the membrane interface. Upon substituting the cyano groups in PIM-1 by various functional groups (hydroxyl, amine, amidoxime, tetrazole and carboxyl), the functional PIMs generally exhibit larger swelling degrees in methanol and higher methanol permeability, surpassing many existing OSN membranes. This simulation study provides microscopic insights into the effects of functionalization on OSN and reveals the complex interplay of solute-solvent-membrane interactions in governing OSN performance.