Layer-by-layer assembly of TpPa-SO ₃ H/TpEB composite membranes for nanofiltration

Layer-by-layer assembled covalent organic framework membranes were fabricated by alternately depositing negatively charged TpPa-SO 3 H and positively charged TpEB nanosheets onto a pretreated nylon support via vacuum filtration. The resulting TpPa- SO 3 H/TpEB composite formed a compact selective layer stabilized by electrostatic attraction and π-π stacking. By optimizing the layer number and deposition density, the bilayer membrane achieved 99.3% Congo Red rejection with a permeance of 86.0 L m -2 h -1 bar -1 and >99% rejection for multiple dyes, with a molecular weight cutoff of 461.38 Da.