Post–Synthetic Modification of MOF–808 for Mixed Matrix Membranes with High and Stable Ion Separation Capacity

The global clean water crisis is a pressing sustainable development challenge that demands urgent solutions. Membrane separation technology has emerged as a leading approach for seawater desalination, offering great potential to address freshwater scarcity. However, achieving both high water flux and high salt rejection in desalination membranes remains a major challenge. Mixed matrix membranes (MMMs), which combine polymer substrates with functional fillers, have shown promise, but their performance is often limited by poor compatibility between the embedded materials and the polymer matrix. In this work, a post-synthetic modification of the metal-organic framework MOF-808 was carried out to improve the interfacial compatibility between the modified MOF-808-SP and polyethersulfone substrate. Remarkably, increasing the loading of MOF-808-SP sustained the membrane selectivity while simultaneously enhancing water flux. This performance contrasts with membranes containing unmodified MOF-808, highlighting the crucial role of improved MOF-polymer compatibility in achieving synergistic separation performance.