A ferroelectric-induced few-nanometer-thick graphene membrane enables molecular sliding for ultra-fast separation

Graphene's atomically smooth surface offers a promising platform for achieving superlubricity, not only in solid-state contacts but also in mass transport. While its ability to minimize interfacial friction has been extensively explored in microelectromechanical systems, engines and biomedical implants, harnessing this property for near-frictionless molecular flow to enable ultra-fast permeation remains a fundamental challenge. The principal limitation lies in the fabrication of defect-free graphene membranes with an exposed surface for probing intrinsic molecular friction and the associated transport phenomena. Here, we demonstrate a ferroelectric-polarization-assisted strategy for fabricating a 3.5-nm-thick graphene skin membrane for ultra-fast and selective separation. This is achieved by electrospinning a graphene oxide (GO)-poly(vinylidene fluoride) (PVDF) mixture, followed by thermal reduction. The crucial step involves the electric-field-induced transition of PVDF from the paraelectric (α) to the ferroelectric (β) phase, which promotes ordered chain packing and reduces the polymer's affinity for GO, thereby driving the spontaneous segregation of GO to the PVDF nanofiber surface. The resulting graphene surface minimizes interfacial interactions with permeating molecules, reducing the molecular flow friction coefficient by 2-3 orders of magnitude. Acting either as a selective layer or a support, the membrane exhibits ultra-fast permeation of water and organic solvents, surpassing current state-of-the-art membranes for water and solvent purification. For instance, a water flux up to 105.1 L m^{- 2} h^{- 1}, a salt rejection of >99.99% and long-term stability of 1000 h are achieved for desalination of hypersaline with salt concentrations >150 g L^{- 1}. This work establishes a new paradigm for realizing ultra-fast molecular transport and provides a versatile platform for investigating nanoscale fluidics at material interfaces.