High-flux and stability nanofiltration membranes prepared with β-cyclodextrin and in-situ co-polymerized of TpPa COFs for dye desalination

Polyester membranes are increasingly utilized in wastewater treatment due to their chlorine resistance. Nonetheless, they face challenges such as limited permeability. The integration of covalent organic frameworks (COFs) can significantly enhance the performance of nanofiltration membranes. However, the heterogeneous dispersion of COFs in solution results in poor compatibility with polyester membranes, leading to increased membrane defects and compromising nanofiltration performance. This study presents the development of COFs-polyester hybrid membranes via a simple one-step in-situ co-polymerization method. During the interfacial polymerization (IP), p-phenylenediamine (Pa) and 1,3,5-triformylphloroglucinol (Tp) were integrated into a β-cyclodextrin (β-CD) aqueous solution and a trimesoyl chloride (TMC) organic solution, respectively. The uniform dispersion of COFs monomers within the IP monomer solution addressed heterogeneity issues, improving compatibility with polyester membranes. The in-situ co-polymerized COFs not only enhanced the sieving capabilities but also improved the hydrophilicity, and free volume of the membranes. The optimized membranes demonstrated a permeance of 105 L/m 2 ·h·bar, with rejection rates of 98.5 % for Congo red and 6 % for Na 2 SO 4 . Moreover, these membranes exhibited remarkable resistance to chlorine, organic solvents, and antifouling capabilities. This study offers novel insights into the application of COFs in polyester membranes, providing a straightforward, cost-effective, and scalable integration strategy.