Amidoxime-functionalized polymer of intrinsic microporosity (AOPIM-1)-based thin film composite membranes with ultrahigh permeance for organic solvent nanofiltration

Advanced organic solvent nanofiltration (OSN) membranes with high permeance and stability are highly needed in petrochemical and pharmaceutical industries. Recently, polymers of intrinsic microporosity (PIMs) have attracted significant attention for the development of advanced membranes, because of their high porosity and solution processability. In this study, a thin film composite membrane based on an amidoxime-functionalized PIM (AOPIM-1) was prepared by spin coating followed by solvent activation. The activation approach could dramatically improve the solvent permeance of the membrane without compromising its rejection performance. The changes in porosity of the AOPIM-1 layer before and after activation were confirmed by positron annihilation Doppler spectroscopy. The optimum membrane exhibited an impressively high ethanol permeance of 15.5 L m−2 h−1 bar−1, nearly one orders of magnitude higher than that of Starmem240 (a commercial polyimide-based OSN membrane) with a comparable rejection of Rose Bengal (MW 1017 Da). In addition, the present membrane exhibited outstanding stability in polar solvents and a remarkably high rejection of active pharmaceutical ingredients (vitamin B12) from ethanol. This work could provide a new avenue for developing highly permeable OSN membranes and is expected to stimulate the use of PIM membranes in OSN applications.