The petrochemical, chemical, and pharmaceutical industries need separation processes to purify chemicals and solvents in addition to recovering valuable catalysts. Traditional methods such as adsorption, distillation, extraction, and evaporation are energy-intensive and can account for up to 40 - 70 % of total production costs. In contrast, Membrane-based separation technologies are recognized as energy-efficient alternatives to conventional, thermal separation methods due to their low carbon footprint, small space requirement, and operation without phase transitions. In this context, advanced organic solvent nanofiltration (OSN) membranes have emerged as a promising alternative for relatively low temperature separations that involve aggressive chemical environments. Although inorganic materials have extraordinary solvent and thermal stability, they have several drawbacks, such as scaling-up problems, high cost, and poor mechanical properties. To address these limitations, organic polymeric membranes, such as polyamide, polyacrylonitrile, cellulose acetate, and silicone, have attracted attention for OSN applications owing to their lower cost, easier scalability, and simple processing. However, their susceptibility to swelling or dissolution in organic solvents can affect their performance and long-term stability. Therefore, novel polymeric materials with improved resistance to organic solvents are needed for OSN. In this study, we present a novel polymer, poly(isatin fluorene), with a tert-butyloxycarbonyl (BOC) group grafted to the isatin unit (PIF-BOC). This polymer exhibited excellent solubility in chloroform, allowing for surface coating to fabricate thin-film composite (TFC) membranes. Commercial polyacrylonitrile (PAN) membranes were coated with a thin PIF-BOC selective layer (~100 nm thickness), forming a shiny, smooth, and homogeneous surface. FTIR analysis confirmed the effective lamination of the barrier layer, as proven by the characteristic three carbonyl peaks of PIF-BOC. The resulting TFC membranes displayed promising separation performance with permeance values of 0.4 - 2.1 Kgh-1m-2bar-1 and n-octane/iso-cetane separation factor of ~ 1.2 -1.9, comparable to commercial silicone-based OSN membranes while offering cost savings of over threefold. These findings highlight the potential of PIF-BOC as a cost-effective and scalable material for advanced OSN membrane applications.
