Ultrafast ion sieving using nanoporous polymeric membranes

The great potential of nanoporous membranes for water filtration and chemical separation has been challenged by the trade-off between selectivity and permeability. Here we report on nanoporous polymer membranes with an excellent balance between selectivity and perme- ability of ions. Our membranes are fabricated by irradiating 2-μm-thick polyethylene ter- ephthalate Lumirror® films with GeV heavy ions followed by ultraviolet exposure. These membranes show a high transport rate of K+ ions of up to 14 mol h−1 m−2 and a selectivity of alkali metal ions over heavy metal ions of >500. Combining transport experiments and molecular dynamics simulations with a polymeric nanopore model, we demonstrate that the high permeability is attributable to the presence of nanopores with a radius of ~0.5 nm and a density of up to 5 × 1010 cm−2, and the selectivity is ascribed to the interaction between the partially dehydrated ions and the negatively charged nanopore wall.This work was supported by National Science Foundation of China (Grant Nos. 11335003 and 31670852) and the National Magnetic Confinement Fusion Energy Research Project of China (2015GB113000). F.L. acknowledges the support from Peking University’s 100-talent plan. P.K. acknowledges the Australian Research Council for financial support. Christina Trautmann acknowledges support from the Deutsche Forschungsgemeinschaft (DFG-FOR1583