Preparation of a triazine porous organic polymer thin film by nanoparticle-polymer reticulation for high-efficient molecule/ion separation

Abstract

Porous organic polymer (POP) membranes show great promise for the precise separation of organic molecules and salt ions due to their high porosity, tunable pore aperture, and robust porous structure. However, their application is hindered by the poor processability of POPs and complicated and uncontrollable membrane preparation. Herein, we report a nanoparticle-polymer reticulation (NPR) strategy by bridging POP nanoparticles for the fabrication of POP nanochannel membranes with a relatively large area (>700 cm²). A new type of water dispersible and processible triazine porous organic polymer (TPOP) nanoparticles was synthesized via the facile and straightforward Debus–Radziszewski reaction. Chitosan (CS) macromolecules as the bridge tied the self-assembled TPOP nanoparticles into a thin film via in situ chemical cross-linking on a polymeric porous substrate, wherein the resultant film thickness, pore size and separation performance could be conveniently tuned. The NPR strategy enabled the construction of an ultrathin and continuous nanochannel TPOP-CSM membrane, presenting both a high water permeance of ∼130 L m⁻² h⁻¹ bar⁻¹ and dye/salt selectivity of ∼35, which is one order of magnitude higher than that of conventional polymeric nanofiltration membranes. Meanwhile, the membrane exhibited good fouling resistance and antibacterial properties in an aqueous environment. Our strategy may provide a paradigm shift in engineering POP nanomaterials and constructing next-generation advanced separation membranes.