Nanopore desalination technology hinges on high water-permeable membranes, which, at the same time, block ions efficiently. In this study, we consider a recently synthesized [<i>Science</i> <b>363</b>, 151–155 (2019)] phenine nanotube (PNT) for water desalination applications. Using both equilibrium and non-equilibrium molecular dynamics simulations, we show that the PNT membrane completely rejects salts but permeates water at a rate which is an order-of-magnitude higher than that of all the membranes used for water filtration. We provide the microscopic mechanisms of salt rejection and fast water-transport by calculating the free-energy landscapes and electrostatic potential profiles. A collective diffusion model accurately predicts the water permeability obtained from the simulations over a wide range of pressure gradients. We propose a method to calculate the osmotic pressure (Π) from the simulation data and find that Π across the membrane is very low (∼1-2 MPa), which thus makes it a suitable nanomaterial for energy-efficient reverse osmosis. These remarkable properties of PNT can be applied in various nanofluidic applications, such as ion-selective channels, ionic transistors, sensing, molecular sieving, and blue energy harvesting.

Highly permeable phenine nanotube membranes for water desalination

ACS Spring Meeting 2021

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