Continuous layered subnanometer-scale channels show great promise for molecular sieving applications. Behavior suitable for such applications has been demonstrated for graphene and its derivatives, but these materials often suffer from poor stability in aqueous environments. There are methods to improve the stability using binders, but these approaches are costly and require additional steps.

Hyung Gyu Park, Swiss Federal Institute of Technology (ETH) Zurich, Switzerland, and colleagues have prepared a layered membrane made of MoS₂ that does not require any additives. Using a sequential procedure comprising chemical exfoliation, centrifugation, and vacuum filtration, they obtained a material with an interlamellar spacing of 6.2 Å. The structure did not change after prolonged soaking in strongly acidic or basic solutions, and the membrane showed gas-tightness and water permeability.

The researchers found that small organic molecules such as methanol can pass through the channels, while larger ones such as 1-propanol are blocked. In addition, diffusion selectivity for aqueous ions was found, thereby making this new material interesting for applications in separation technology and for the study of molecular transport phenomena.

• Stability, Molecular Sieving, and Ion Diffusion Selectivity of a Lamellar Membrane from Two-Dimensional Molybdenum Disulfide,
  Mengmeng Deng, Kijeong Kwac, Meng Li, Yousung Jung, Hyung Gyu Park,
  Nano Letters 2017.
  DOI: 10.1021/acs.nanolett.6b05238