Dipole moment mediated molecule transport behaviors in charged vertically-aligned 2D nanochannels

Nanochannel-molecule interactions are of paramount importance for molecule transport in confined nanochannels. Except for molecular solubility parameter, molecular dipole moment highly affects the electrostatic interactions with charged nanochannels, but its influence on molecule transport has yet been elucidated. The precise molecule separation based on dipole moment difference is therefore rarely reported. Herein, vertically-aligned nanochannel membranes with tunable charge properties were fabricated, the charge intensity of which was adjusted by regulating various functional groups ( CH 3 , NH 2 , F 3 ). Based on these robust and long-range 2D nanochannels, the influence of molecule dipole moment on its transport behaviors is explored for the first time. We demonstrate that compared with non-polar molecules, polar molecules with obvious dipole are induced to generate an induced dipole moment (D id ) in charged nanochannels. Molecules with small intrinsic dipole moments (D in ) exhibit a high dipole variation (over 73.5%) caused by the electrostatic interaction, leading to a high dependence of their permeance on the charge intensity of nanochannels. In contrast, molecules with large intrinsic dipole moments display negligible dipole variation (below 7.9%), and their permeance shows weak fluctuations to the charge intensity of nanochannels. Furthermore, we reveal that the total dipole moment (D t ) dominates the electrostatic interaction strength of molecules with the charged nanochannels, which affects the transport permeance. The permeance adheres to the formula: P = k 1 μ D t 2 r 0.5 V ( μ , viscosity; D t , total dipole moment; r , molecule diameter; V , charge intensity of nanochannel). Accordingly, a high separation factor of 8.36 for ethanol/water is achieved for charged membrane.