Highly Permeable MoS₂ Nanosheet Porous Membrane for Organic Matter Removal

MoS₂ nanosheets were synthesized by a bottom-up green chemical process where l-cysteine was used as a sulfur precursor. With specific concentrations, molar ratio of reactants, and pre-mixing conditions, MoS₂ nanosheets of 200-300 nm in size and 4.2 nm in average thickness were successfully obtained. Porous membranes were then prepared by depositing the MoS₂ nanosheet suspension on a 0.1 μm pore size poly(vinylidene difluoride) membrane filter in a multiple batch procedure. The membrane deposited with 12 batches of MoS₂ nanosheets achieved 93.78% removal of bovine serum albumin. Acid red removal of 95.65% was also achieved after the second filtration pass. The porous MoS₂ nanosheet membrane also demonstrated a high water flux of 182 ± 2.0 L/(m² h). This result overcame the trade-off between selectivity and permeability faced by polymeric ultrafiltration membranes. The MoS₂ nanosheets as building blocks formed not only intersheet slit pores with a narrow half-width to restrict the passage of organic molecules but also macro-channels allowing easy passage of water. The assembled MoS₂ nanosheet membrane delivered promising separation of protein molecules and a high flux, attributing to its porous nanostructure, and could be a potential membrane for various water applications.