Scalable synthesis of ultrathin MoS2 membranes for dye desalination

Molybdenum disulfide (MoS2) has been fabricated into thin-film composite (TFC) membranes for dye desalination due to its excellent underwater stability and tunable interlay spacing. However, it remains challenging to synthesize thin layers of MoS2 with high water permeance and high dye rejection due to the difficulty in fabricating large crystalline sheets or exfoliation. Herein, we report a scalable method coupling bottom-up hydrothermal synthesis and top-down ultrasonic exfoliation to obtain well-dispersed MoS2 nanosheets and a vacuum filtration method to prepare ultrathin membranes (thickness: 30 – 60 nm) for dye desalination. The MoS2 nanosheets and membranes are thoroughly characterized for their chemistries and nanostructures. The membrane with 60-nm MoS2 exhibits water permeance of 32 LMH/bar, Na2SO4 rejection of 2.3%, and Direct Red-80 rejection of 99.0%. The MoS2 membranes exhibit dye desalination performance superior to state-of-the-art commercial polyamide membranes and many leading membranes based on two-dimensional materials.