A graphene-like membrane with an ultrahigh water flux for desalination

YG Yan and WS Wang and W Li and KP Loh and J Zhang, NANOSCALE, 9, 18951-18958 (2017).

DOI: 10.1039/c7nr07193k

An ultrathin nanoporous membrane which combines high water permeability and high salt rejection is the core of ultrafiltration technology. Recently, we reported the synthesis of a chemically robust and nanoporous two-dimensional conjugated aromatic polymer (2D-CAP) membrane. Due to its array of highly regular sub-nanometer pores and channels, the ultrathin 2D-CAP membrane can be potentially used in desalination. Herein, we used molecular dynamics simulations to analyze the transmembrane hydrodynamics of mono-and multi-layer 2D-CAP membranes as a function of layer number. The energy barriers to water and ions across these membranes were calculated to evaluate the potential of 2D- CAP to function as the ultimate RO membrane. Our simulation results show that the bilayer CAP membrane exhibits superior ion rejection (100%) and a water flux (1172 L m(-2) h(-1) bar-1) with a performance that is three orders of magnitude higher than the commercial reverse osmosis membrane, which is three times higher than the theoretically reported monolayer nanoporous MoS2 membrane (the state-of-the-art membrane reported for desalination). In addition, the 2D-CAP bilayer membrane is highly resistant to swelling even at a high water flux. The monolayer 2D-CAP membrane shows good ion selectivity between monovalent and divalent ions.

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