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.