Computational Design of 2D Covalent-Organic Framework Membranes for Organic Solvent Nanofiltration

Covalent-organic frameworks (COFs) are ordered crystalline materials covalently formed by building blocks of light elements. There has been increasing interest in the development of COF membranes for chemical separation. In this study, seven two-dimensional (2D) COF membranes are computationally designed with different functional groups and aperture sizes. By 245 sets of molecular simulations, the seven ultrathin COF membranes are investigated for organic solvent nanofiltration (OSN) of seven solvents (acetonitrile, acetone, methanol, ethanol, isopropyl alcohol, methyl ethyl ketone, and n-hexane) and four solutes (2,5-furandiamine, paracetamol, α-methylstyrene dimer, and Nile red). The solvent fluxes through the COF membranes are revealed to be governed by the aperture size and membrane functionality, as well as solvent properties. In general, the larger the aperture size, the higher is the flux. For membranes with comparable aperture size, the hydrophobic one exhibits higher fluxes than the hydrophilic c...