Polyester membranes with covalent organic frameworks-modified microfiltration substrate via interfacial polymerization for efficient dye nanofiltration

Currently, polyester (PE) membranes prepared using green materials have gained more attention in the membrane separation field. Most of the previously reported PE membranes are synthesized on ultrafiltration substrate, which hinders the enhancement of water permeance. This paper proposes a new strategy to fabricate PE membranes with covalent organic frameworks (COFs) modified microfiltration substrate via interfacial polymerization (IP). On the one hand, COFs modify the Nylon microfiltration substrate while affecting the subsequent IP process to obtain the thinner and smoother selective layer. This process was also analyzed by molecular dynamics (MD) simulation. On the other hand, the excellent hydrophilicity of the PE layer also endowed the anti-fouling properties of the covalent organic frameworks-polyester/Nylon (COF-PE/Nylon) membrane. The optimal COF-PE/Nylon membrane had 99.6 % Congo red (CR) rejection, and dye/salt (CR/NaCl) selectivity was 63.1. Meanwhile, the pure water permeance reached 157.5 L m−2h−1 bar−1, higher than the PE membrane prepared on the ultrafiltration substrate. The present work demonstrated the excellent separation performance of COF-PE/Nylon membranes and provided a reference for subsequent PE membrane preparation on various substrates.