Dynamic covalent interface engineering for 2D MXene membrane with interchangeable surface groups and tunable layer spacing for water treatment

Two-dimensional (2D) MXene-based materials are promising for water purification due to their nanometer interlayers, however, achieving adaptable and engineerable nanochannel surface properties in the 2D MXene membrane remains challenging. We propose a pioneering approach, called dynamic covalent interface engineering (DCIE), to address this issue. A poly (4-vinylphenylboric acid)-grafted MXene membrane was prepared, binding interchangeable diols via dynamic boronic ester chemistry. Alternative diols enhanced interlayer distancing to 1.49–1.60 nm. The interlayer-anchored diols transition from anionic to cationic and from hydrophilic to hydrophobic states through reversible covalent bond formation and cleavage, with no residue effect of previous diols. As a result, the membrane with swiftly tailored nanochannel properties exhibits exceptional switchable permeability and selectivity (98 % for Congo Red, 97 % for Gentian Violet) for various water treatment scenarios. This innovative method presents a promising strategy for fabricating customizable and switchable 2D MXene-based membranes with enhanced molecular transport and sieving effects, thus advancing water purification applications.