Tailoring Separation Performance of Nanofiltration Membranes by Construction of Tin(II)-α-diimine Coordination Bonds in Polyimides

Polyimide nanofiltration (NF) membranes with customizable chemical structures and excellent overall performance have attracted great interest in desalination and wastewater treatment. This work introduced novel Tin(II)-α-diimine coordination interactions to tailor the separation performance of polyimide NF membranes. Microstructural analysis confirmed the successful construction of coordination sites between Tin(II) and the diimine moieties. As expected, the resulting coordinated NF membranes exhibited uniform nanopores and reduced absolute negative charges on their surfaces, facilitating outstanding NF separation. The optimal coordinated polyimide NF membranes exhibited a high rejection rate of over 98% for methylene blue (MB) and a low rejection rate of less than 2% for NaCl and Na2SO4, demonstrating significant potential for application in dye desalination. Additionally, the obtained NF membranes demonstrate better long-term separation stability. As a preliminary study, this work provides a new strategy to modulate the microstructure and surface electric charge of NF membranes, potentially leading to greater application potential in dye desalination, seawater desalination, etc.