Highly porous ultrathin polyamide membranes for fast separation of small molecules from organic solvents

Membranes with permselective performance as well as high stability in harsh solvents are urgently desired for energy-efficient precise chemical separations. In this work, we utilize an adamantane diamine as a molecular building block to fabricate thin-film composite polyamide membranes for high-performance organic solvent nanofiltration (OSN). The bulky, cage-like adamantane structure acts as a molecular-level steric hindrance unit to inhibit polymer chain packing which generating interconnected micropores within the interfacially polymerized polyamide layer. This translates into high membrane methanol permeance of 20.6 L m-2 h-1 bar-1 and 94.7% retention to organic dye molecules with molecular weight down to 327 g mol-1. Furthermore, the membrane demonstrates high stability in different organic solvents taking advantage of the crosslinked rigid structure, which shows constant solute retention throughout a 180 h continuous filtration experiment with a DMF solution containing methyl orange as feed solution. Employing rigid and bulky molecular features in selective layer is thus demonstrated to significantly promote the polyamide membrane permeability and solvent resistance without compromising the overall selectivity.