Self-assembly enabled nano-intercalation for stable high-performance MXene membranes

Two-dimensional (2D) lamellar membranes, such as graphene and MXene based surfaces have attracted growing interest for water purification. However, 2D membranes still face critical challenges, such as low stability, high internal resistance, and the tradeoff between permeability and selectivity, leading to unsatisfactory separation performance. Herein, high-performance MXene membranes with stable and tunable lamellar nanochannels are fabricated by facile self-assembly of negatively charged 2D MXene (Ti3C2Tx) nanosheets and positively charged 0D alumina (Al2O3) nanoparticles. The internal nanochannels (e.g., d-spacing) and surface properties (e.g., hydrophilicity and roughness) of the prepared MXene membranes can be precisely tailored by self-assembly of MXene/Al2O3 with different mass ratios. The optimized membrane with an MXene/Al2O3 mass ratio of 1:1 exhibits an outstanding water permeability of 88.8 LMH/bar (four times higher than that of the unmodified MXene membrane) and high molecule separation performance (>99.5% rejections to Rhodamine B and Methyl Blue). Such high separation performance outperforms many 2D membranes reported in literature, mainly because of the tunable interlayer spacing and favorable surface properties. The optimized MXene membrane also shows significantly enhanced channel stability after nano-Al2O3 intercalation during self-assembly. The selfassembly enabled nano-intercalation demonstrated in this work provides a facile method for engineering highperformance 2D membranes with stable and tunable nanochannels for precise molecular separation.