Nanoparticle-Assembled Thin Film with Amphipathic Nanopores for Organic Solvent Nanofiltration

Polymeric thin film composite (TFC) membranes have been proven promising for a wide range of separation applications. However, their development is significantly hindered by low permeance (below 8.0 L m^-2 h^-1 bar^-1). Here, we report the fabrication of new films with nanoparticle-assembled structure via interfacial polymerization using quantum dots (QDs) as building blocks. The tailored QDs with hydrophobic and hydrophilic regions permit cross-linking into nanoparticle-assembled defect-free thin films. Significantly, amphipathic QDs show good affinity to polar and nonpolar molecules, facilitating their fast dissolution into film. Meanwhile, the nanopores (∼1.4 nm) render fleet diffusion of molecules, which highly promotes the transfer of molecules within the film. This synergetic effect endows the resultant TFC membrane with high permeance, over 2 orders of magnitude higher than the conventional polyamide films. The permeances for acetonitrile and n-hexane reach 46.9 and 50.8 L m^-2 h^-1 bar^-1, respectively. We demonstrate that films fabricated by hydrophilic and hydrophobic QDs exhibit different molecular transfer mechanisms, and the corresponding model equations are established. The film fabricated by amphipathic QDs shows a combination transfer mechanism of the two models. Furthermore, those QD-based TFC membranes display favorable structural and operational stability, holding promise for industrial separation applications.