Hetero-dimensional 1D silk nanofibril and 2D MXene composite membrane with tailorable nanofluidic channels for enhanced water purification

Laminar membranes assembled with two-dimensional (2D) nanosheets, where the confined space provides efficient sieving performance at nanoscale, have attracted widespread interests for precise molecular separation. However, regarding the trade-off effect between selectivity and permeability, as well as the swelling issues of nanosheets, to maintain the stability of 2D laminar membranes remain a great challenge. Herein, 1D silk nanofibers (SNFs) was introduced to 2D MXene nanosheets to design a 1D/2D heterojunction structure for fabricating 2D laminar membrane with tunable interlayer distance and enhanced stability. The SNFs expanded the d-spacing of MXene nanosheets and enhanced the stability of the membranes due to their strong interactions and excellent mechanical toughness. The optimized membrane possessed a remarkable pure water permeability (24.45 L m−2 h−1 bar−1) and dyes rejections (99.41% against congo red (MW: 696.7 Da), 99.43% against xylene brilliant cyanin G250 (MW: 854.0 Da) and 99.08% against methyl blue (MW: 799.8 Da)). Moreover, the decorated membrane exhibited moderate salt rejections against Na2SO4 (64.30%), MgSO4 (14.35%), MgCl2 (3.90%) and NaCl (15.85%), which was rather competitive for separating dye/salt mixed solutions.