Abstract
Natural gas is currently the main industrial source of helium, thus
He/CH4 separation has become increasing important, where
two-dimensional materials have been considered to be a potential
solution, but the gas transport mechanism within nanopores is not yet
clear. Here, both non-equilibrium molecular dynamics (NEMD) and
equilibrium MD (EMD) were employed to study the transport of
He/CH4 through nanopores of different MXenes with
various pore diameters (d ), nanopores’ density and functional
groups, which shows two main transport mechanisms, molecular sieving or
Knudsen diffusion. Small d is found to be crucial for the
molecular sieving mechanism and consequently, high
He/CH4 selectivity (S He/CH4). The
density profiles of He/CH4 along permeation direction
from EMD simulations were used to
predict S He/CH4 and permeance for the gas passing
through different nanopores, yielding results well agreeing with NEMD
simulations. This work provides theoretical insights into gas transport
in MXene nanopore for future nanopore designing engineering.