In-situ COF-modified nanofibrous substrates for construction of high-flux polyamide nanofiltration membrane

The thin-film composite (TFC) membranes fabricated via interfacial polymerization (IP) of polyamide selective layers on porous substrates have prevailed in nanofiltration. An effective porous substrate is expected to play a synergistic role in optimizing the overall membrane performance by reducing transport resistance and promoting the formation of the selective layers. Although electrospun nanofibrous membranes (ENM) with high porosity and interconnected network are inherently engineered as substrates to facilitate transport processes, their poor monomer storage ability impedes the subsequent formation of defect-free polyamide layers. In this work, an in-situ covalent organic framework-modified ENM (COF@ENM) was prepared and employed as a hybrid substrate to construct ultra-thin and defect-free polyamide TFC membranes. The introduction of TpPa-SO₃H COF effectively captures and stores the amine monomers through inherent pores and electrostatic interaction. The optimized PA/COF@ENM membrane achieved a remarkable water permeance of 45.7 ± 0.5 L·m −2 ·h −1 ·bar −1 , while successfully maintaining a high Na 2 SO 4 rejection of 98.6 %. Overall, the outstanding performance of the in-situ TpPa-SO₃H COF-modified nanofibrous substrates-based TFC membrane can lead to new advances in nanofibrous substrates manufacturing.