Engineering hydrophilicity of graphene oxide membranes via poly(ionic liquid)s intercalation for efficient anion separation

Two dimensional (2D) membranes show huge potential for ion sieving applications owing to their regular sub-nanometer channels. How to engineer the channel micro-chemistry to pursue higher ion selectivity while maintaining promising ion transports remains challenging. In this work, we propose building rigidly confined charged 2D graphene oxide (GO) channels and manipulating their hydrophilicity via self-designed poly(ionic liquid)s (PILs) intercalation. The imidazolium cations on the PILs backbone not only stabilize the GO interlayer channels via non-covalent interactions but also create a positively charged environment for attracting anions entering into channels. The hydrophilicity variations of the side chains on the PILs help with realizing the regulation of the channel hydrophilicity. Under the electrodialysis mode, the GO membrane with the strongest hydrophobicity yields an impressive selectivity of 172.2 for Cl⁻ and SO₄²⁻, which is 48 times of Neosepta ACS, a commercial membrane specialized for anion separation. This work offers a brand-new route in exploring high-performance ion selective membranes.