Fabrication and application of high-performance Noria-based organic solvent nanofiltration membranes for low-polarity natural product separation

This research aimed to develop a high-performance organic solvent nanofiltration (OSN) membrane using porous organic cage Noria and nonplanar molecules to separate low-polarity bioactive components from a representative herbal extract and remove pigments like chlorophylls. The OSN membranes were fabricated and further modified via interfacial polymerization on polysulfone (PSF) ultrafiltration substrates. Among the fabricated membranes, the OSN-10 membrane, prepared by interfacial polymerization of Noria and cyclohexane-1,3,5-tricarbonyl chloride (HTC), demonstrated noteworthy performance. It demonstrated high solvent permeance of both methanol (29.28 L m−2h−1bar−1) and ethanol (16.98 L m−2h−1bar−1). Importantly, a bioactive stilbene, cajaninstilbene acid (CSA), was successfully enriched from pigeon pea leaf extracts using OSN-10 membrane while maintaining a high chlorophyll rejection rate of over 90 %. The Noria-based OSN-10 membrane developed in this work exhibited impressive organic solvent permeability and an optimal molecular weight cut-off, making it highly suitable for CSA separation. Overall, the OSN-10 membrane demonstrated excellent separation performance, remarkable chlorophyll rejection rate, and significant potential for application in low-polarity natural product separation. Also, the membrane process significantly reduces the use of organic solvents, simplifies isolation and purification, and offers cost advantages with industrialization potential compared to traditional solvent extraction methods.