Covalent organic framework modified polyamide nanofiltration membrane with enhanced performance for desalination

A novel thin film nanocomposite (TFN) membrane was prepared by incorporating covalent organic frameworks (COFs) into polyamide (PA) layer on a polyether sulfone (PES) substrate, through interfacial polymerization method. The porous structure of COFs (SNW-1) provided more passageway for water transport. Meanwhile, the reaction between SNW-1 and trimesoyl chloride (TMC) during interfacial polymerization formed strong covalent bonds for better interface compatibility. The surface hydrophilicity of the hybrid membrane was improved due to the existence of amine-rich SNW-1. The influence of the interfacial polymerization conditions and piperazine (PIP) and the loading of SNW-1 on the membrane performance were investigated. The resultant PA-SNW-1/PES membrane with a SNW-1 loading of 1 g/m2 exhibited an increased pure water flux from 100 L m−2 h−1 MPa−1 to 192.5 L m−2 h−1 MPa−1 compared to the pristine PA membrane while the rejection to Na2SO4 maintained above 80%. Moreover, the membrane also showed long-term running stability.