Desalination behavior of composite membrane with petal shaped pore—formed by superimposition of covalent organic framework with large aperture difference

•The composite membrane with six “petals” shaped pores is constructed.•The desalination performance of composite is tested by MD simulation.•The composite membrane can simultaneously obtain high water flux and ion rejection.•Small aperture and large surface contribute to superior desalination performance.•Water permeance can be improved by properly increasing the layers spacing.