Graphene quantum dots (GQDs)-assembled membranes with intrinsic functionalized nanochannels for high-performance nanofiltration

Abstract

Recent innovations highlight the great potential of zero-dimensional materials of graphene quantum dots (GQDs) as attractive candidates for fabricating advanced nanofiltration membranes. In this study, a novel class of thin-film composite (TFC) nanofiltration membranes derived from assembled GQDs with amino/sulfonic modification (GQDs_N/S) as building blocks directly, is developed to achieve highly selective water transport for high-performance nanofiltration via interfacial polymerization. Based on the transport behavior, the intrinsically hydrophilic sulfonic groups are introduced to endow the membrane with stronger internal polarity and more accessible sites for easier water molecules infiltration, while engineering the nanochannels by covalently immobilizing GQDs between the terminal amino groups and trimesoyl chloride. Furthermore, an enhanced interparticle space with enlarged free volumes between GQDs is obtained for rapidly transporting water molecules inside the membrane, owing to the intercalation of sulfonic groups acting as spacers to break up the tightly stacking structure of GQDs. The resultant GQDs_N/S TFC membrane exhibits superior separation properties with high water permeance of 9.82 L m-2h−1 bar−1 and 97.4% rejection against Na2SO4, giving rise to more than 2-fold higher water permeability without obviously sacrificing the membrane selectivity, and revealing an outperformed separation property when compared to state-of-the-art nanofiltration membranes. Simultaneously, the sulfonic and amino sites firmly anchored on GQDs with custom-tailored functionality further enables the GQDs_N/S TFC membrane to perform an outstanding antifouling property and durability over the long-term operation condition. The proposed approach opens new pathways to fabricate highly permeable-selective nanofiltration membranes.