Aminated graphene quantum dots intercalated MXene composite membranes for highly efficient dye/salt separation

Two-dimensional (2D) lamellar membranes exhibit great potential for efficient dye/salt separation, owing to their tunable interlayer channel structures and excellent molecular sieving selectivity. However, irregular stacking of 2D nanosheets and weak interlayer interactions often induce membrane swelling in aqueous environments, severely limiting their practical application prospects. In this study, a MXene composite membrane with structural stability, regular stacking, and outstanding permeability and selectivity was fabricated by incorporating zero-dimensional (0D) partially aminated graphene quantum dots (NGQDs) into MXene nanosheets. The experimental results demonstrate that 0D NGQDs can stably bind to MXene nanosheets via non-covalent interactions and disperse uniformly. The exposed amino groups on GQDs not only optimized the stacking structure of MXene layers but also enhanced interlayer forces by providing specific binding sites, thereby effectively alleviating the aqueous swelling issue of MXene membranes. The optimized composite membrane exhibited excellent rejection of Congo Red (CR) (>99 %), remarkable dye/salt separation efficiency, and long-term operational stability. Specifically, the separation factors for CR/NaCl and CR/Na 2 SO 4 mixed solutions reached 697 and 740, respectively, outperforming most 2D lamellar membranes and nanofiltration membranes reported in literature. This work provides valuable insights for the development and application of high-performance 2D lamellar membranes.