Empirical indication for desalinating properties of porous boron nitride

In recent years, inorganic 2D materials have been recognized as promising candidates for membrane filtration. In particular, theoretical studies predict the excellent desalination performance of nanoporous hexagonal boron nitride. However, studies showing the experimental realization of such systems are to this date missing. In this work, we demonstrate the desalinating properties of sp2-bonded boron nitride. Secondary Ion Mass Spectrometry experiments have shown the clear separation of NaCl and water by the boron nitride film: Na and Cl ions have been retained and trapped in the near-surface region, while water permeated through its whole depth. Analysis based on the diffusion equation revealed that the diffusion coefficient of water is over 3 orders of magnitude higher than the diffusion coefficient of NaCl in the temperature range of 25-65°C, manifesting that boron nitride is a material of high potential for use as a selective layer for membrane filtration.