Ultrathin poly (vinyl alcohol)/MXene nanofilm composite membrane with facile intrusion-free construction for pervaporative separations

Abstract Molecular separations using synthetic membranes have been widely recognized as energy-efficient processes relative to conventional separation technologies. Rational design of the membrane structures for attainment of exceptionally permselective materials is highly beneficial in this respect. Herein, an ultrathin organic-inorganic hybrid nanofilm is formed on a hydrophobic polytetrafluoroethylene porous substrate through a facile and scalable solution casting process, thereby realizing an intrusion-free composite structure. Nanosizing Ti3C2Tx MXene and sulfosuccinic acid are incorporated as nanofiller and crosslinker to manipulate the structural rigidity and free-volume property by polymer-nanofiller interaction and polymer chain crosslinking while simultaneously rendering outstanding membrane transport property, selectivity and stability. The synthesized nanofilm composite membrane with thickness down to ≈230 nm, comparable with the lateral dimension of small-sized MXene (≈142 nm), exhibits outstanding pervaporative separation of water from various aqueous-ion or -alcohol mixtures with high throughput that is around 5–70 times of other reported polymer-based membranes. Transport modelling of this hybrid nanofilm suggests that ultralow-resistance permeation behavior induced by MXene nanosheets dominates as the nanofilm thickness approaches the filler size.