Fabrication of molecularly porous hyper-cross-linked thin film composite nanofiltration membrane using cyclic amine and linear cross-linker for highly selective organic solvent nanofiltration

A thin film composite molecularly porous hyper-cross-linked (TFC-MPCM) polyamide nanofiltration membrane was fabricated by interfacial polymerization using macrocyclic amine and linear cross-linker with acid chloride function at para-positions. The membrane was thoroughly characterized using Attenuated Total Reflectance-Fourier Transform Infra-red spectroscopy (ATR-FTIR), solid Cross Polarization-Magic Angle Spinning (CP-MAS) ¹³C NMR, Field Emission-Scanning Electron Microscopy (FE-SEM), Atomic Force Microscopy (AFM), Water Contact Angle (WCA), X-ray photoelectron spectroscopy (XPS) and Energy Dispersive X-ray spectroscopy (EDX) analysis showing the formation of continuous and dense polyamide active layer on the support. The membrane showed excellent performance in terms of permeate flux of the tested solvents including water, methanol, ethanol, isopropyl alcohol, acetone, n-hexane, and toluene. Membrane selectivity tests showed a rejection of >94% of Congo red (solute) from organic solvent (methanol) at 4 bar with a flux of 18.0 L m⁻² h⁻¹. The TFC-MPCM showed exceptional long-term stability in terms of rejection and flux.