Division of Physical Science and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
School of Science and Technology, Nottingham Trent University, Nottingham, NG11 8NS, UK
Two-dimensional covalent organic framework (COFs) membranes have shown promise for organic solvent nanofiltration applications. However, the ability to modulate the chemical properties of the membranes and their effects on the molecular transport process has not yet been explored. Here, we demonstrate the synthesis of two COF membranes (TFP-MPOHF and TFP-MPF) with the same scaffold structures but different internal chemical properties. The presence of hydroxyl groups in the TFP-MPOHF membranes resulted in a significant improvement in polar solvent permeability. In contrast, the hydrophobic TFP-MPF membranes offered excellent permeability to nonpolar solvents, which was 130 – 235% higher than the TFP-MPOHF and commercial polymeric membranes. In addition, both COF membranes exhibited precise molecular sieving capacity with an apparent molecular weight cut-off (MWCO) of 800 g mol-1 and excellent stability. A deviation from the pore-flow model was observed for the TFP-MPOHF membranes, which was due to the specific interactions between solvent molecules and polar channel walls.