Hydrophobic fluorinated graphene templated molecular sieving for high efficiency seawater desalination

The scarcity of freshwater is of great challenge that the world is facing nowadays. The advances of nanomaterial based on the reverse osmosis (RO) technology provide new possibilities for desalination. In this study, using molecular dynamics simulation, we propose and design an excellent RO membrane composed of fluorinated graphene (F-GRA) nanochannels, by which the exceptionally high water permeation (reaching up to 61.1 L/cm(2)/ day/MPa) and the almost complete ion rejection are achieved. Notably, F-GRA nanochannel membranes exhibit a desalination performance much more promising than many other nanomaterials in previously theoretical studies. This superior desalination performance of F-GRA channels is attributed to the negatively charged surface and hydrophobicity of F-GRA, where the electrostatic interactions (attraction or repulsion) between ions and F -GRA surface cause the ideal ion rejection and the ultralow water friction on F-GRA mediated by its hydropho-bicity results in the excellent water penetration. Moreover, potential of mean force calculations further reveal that the water molecule reflects the lowest free energy barrier relative to ions when traversing through the F-GRA channel, indicating the energetical favorability of the successful water transport instead of ions. Our theoretical study offers a fascinating approach of molecular sieving design usable for future desalination.