Solvent-resistant triazine-piperazine linked porous covalent organic polymer thin-film nanofiltration membrane

We present the fabrication of a novel porous covalent organic triazine-piperazine based membrane (CTP membrane) for solvent nanofiltration. The porous CTP skin layer grows on the top surface of polyacrylonitrile (PAN) support in presence of N, N-diisopropylethylamine (DIPEA) in the water/heptane interfacial reaction. The CTP skin layer membrane showed solvent-resistant property to a wide range of common solvents such as DMF, DMSO, and NMP; the stability of the composite membrane is limited by the PAN support. Chemical bonding and elemental analyses confirm the incorporation and linking of the triazine and piperazine components in the nanofilms skeleton. Electron microscopic image analysis demonstrates that the CTP skin layer nicely covers the PAN support and has porous and crumple morphology. The membrane exhibits excellent NF properties as demonstrated by the selective dye rejection and salt rejection experiment. The CTP membrane showed dye rejection (Reactive black-5; MW 992 gmol⁻¹) and salt rejection (Na₂SO₄) 96.7%, and 91.3%, respectively. The membrane comprised a stable porous robust structure, large surface area, well-defined pore topology, and solvent durability coupled with the zeta potential. All of these cooperatively benefits to achieve superior performances in separation, reusability with high permeance, leading to state of the art performance in the NF application.