Surface/interfacial transport through pores control desalination mechanisms in 2D carbon-based membranes

Abstract

The shortage of freshwater is a critical concern for contemporary society, and reverse osmosis desalination technology has gathered considerable attention as a potential solution to this problem. It has been recognized that the desalination process involving water flow through angstrom-sized pores has tremendous potential. However, it is challenging to obtain angstrom-sized pore structures with internal mass transfer and surface/interface properties matching the application conditions. Herein, a two-dimensional (2D) zeolite-like carbon structure (Carzeo-ANG) was constructed with unique angstrom-sized pores in the zeolite structure; then, the surface/interfacial transport behavior and percolation effect of the Carzeo-ANG desalination membrane were evaluated by density functional theory (DFT) calculations and classical molecular dynamics. The first-principles calculations in density functional theory were implemented through the Vienna ab initio simulation package (VASP), which is a commercial package for the simulation of carbon-based materials. The results show that Carzeo-ANG is periodically distributed with angstrom-sized pores (effective diameter = 5.4 Å) of dodecacyclic carbon rings, which ensure structural stability while maintaining sufficient mechanical strength. The remarkable salt–ion adsorption properties and mass transfer activity combined with the reasonable density distribution and free energy barrier for water molecules endow the membrane with superior desalination ability. At the pressure of 80 MPa, the rejection efficiency of Cl⁻ and Na⁺ were 100% and 96.25%, and the membrane could achieve a water flux of 132.71 L cm⁻² day⁻¹ MPa⁻¹. Moreover, the interconnected electronic structure of Carzeo-ANG imparts a self-cleaning effect.