Abstract
Many researchers have examined the desalination performance of various kinds of two-dimensional (2D) porous nanosheets prepared by top-down approaches such as forming pores on the plain based on molecular dynamics (MD) simulations. In contrast, it is rare to find MD simulations addressing the desalination performance of a 2D porous nanosheet prepared by bottom-up approaches. We investigated the desalination performance of a 2D porous nanosheet prepared by the assembly of cucurbit[6]uril (CB[6]) via MD simulation. The model 2D CB[6] nanosheet features CB[6] with the carbonyl-fringed portals of 3.9 Å and the interstitial space filled with hydrophobic linkers and dangling side chains. Our MD simulation demonstrated that the 2D porous CB[6] nanosheet possesses a 70 to 140 times higher water permeance than commercial reverse osmosis membranes while effectively preventing salt passage. The extremely high water permeance and perfect salt rejection stem from not only CB[6]’s nature (hydrophilicity, negative charge, and the right dimension for size exclusion) but also the hydrophobic and tightly filled interstitial space. We also double-checked that the extremely high water permeance was attributable to only CB[6]’s nature, not water leakage, by contrasting it with a 2D nanosheet comprising CB[6]-spermine complexes. Lastly, this paper provides a discussion on a better cucurbituril homologue to prepare a next-generation desalination membrane possessing great potential to such an extent to surpass the 2D porous CB[6] nanosheet based on quantum mechanics calculations.
Highlights
Two-dimensional (2D) nanomaterials such as graphene oxide or MXenes have received much attention as a compelling alternative for membrane fabrication owing to their unique properties capable of inducing low frictional water flow through the interlayer spacing in recent years [1,2]
The possibility of improving the desalination performance of porous single-layer nanosheets has been reported consistently through molecular dynamics (MD) simulations accompanied by the modification of pore designs or desalination conditions up to recently [15,16,17]
We carried out MD simulations using the GROMACS 4.5.3 package [30] to predict the desalination performance of a 2D porous CB[6] nanosheet
Summary
Two-dimensional (2D) nanomaterials such as graphene oxide or MXenes have received much attention as a compelling alternative for membrane fabrication owing to their unique properties capable of inducing low frictional water flow through the interlayer spacing (or d-spacing) in recent years [1,2]. The possibility of improving the desalination performance of porous single-layer nanosheets has been reported consistently through MD simulations accompanied by the modification of pore designs or desalination conditions up to recently [15,16,17]. Among several synthetic water channels, cucurbituril homologues, which are macrocycles with sub-nanometer pores [23,24,25], can be considered as a promising candidate for selective water transport owing to its well-defined channel structure and carbonyl-fringed portal This material has not yet been explored as a single-layer membrane in spite of its great potential. We utilized the polarizable continuum model (PCM) to model the water environment for the QM calculation
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