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

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 approximate to 230 nm, comparable with the lateral dimension of small-sized MXene (approximate to 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.