Preparation and ion separation properties of sub-nanoporous PES membrane with high chemical resistance

The sub-nanochannel materials have attracted extensive attention because of the great potentials in ion separation and water filtration due to their unique ionic transport properties. However, effectively preparing the sub-nanoporous membranes with tunable channel size is still a challenge. In this study, a green and convenient method is introduced to prepare sub-nanoporous polyethersulfone (PES) membrane with highly aligned channels by swift heavy ion irradiation, UV sensitization, and water rinse. Through adjusting the membrane's UV sensitization time, the channel diameter of sub-nanoporous PES membrane can be facilely regulated at sub-nanoscale, which is essential to design the tailor-made membranes for specific applications. It is found that ionic transport in sub-nanoporous PES membrane exhibits voltage-activated features associated with the ionic dehydration at angstrom-confined space, with the corresponding I−V characteristics showing a dependence on ion species, channel size, and solution pH. Such a membrane can work as an excellent ion-exchange membrane in electrodialysis ion separation, exhibiting a separation ratio of K+:Na+:Li+:Mg2+ as high as 83:56:14:1 and K+ transport rate up to 0.82 mol h−1 m−2 under 10 V driving force. It is proved that the sub-nanoporous PES membrane also possesses strong chemical and electrochemical tolerances, which are the prerequisites for future utilizations.