(45h) Tunable Edge Charges As a New Paradigm for Designing Optimal Two-Dimensional Desalination Membranes

Heteropolar two-dimensional materials exhibit pronounced electrostatic interactions at the solid-liquid interface, facilitating unique nanoscale transport pathways and modulation of interfacial properties. Here, we demonstrate that functional groups, including hydrogen, hydroxyl, and oxo, can modulate charges differently at boron and nitrogen terminated edges of nanopores in hexagonal boron nitride, leading to highly selective membranes for salt and boron rejection. Using quantum mechanically computed charge distributions in molecular simulations reveals that hydrogen-functionalized boron-terminated pores and oxygen-functionalized nitrogen-terminated pores demonstrate superior salt rejection of close to 100%, due to roughly neutral edge atoms which offer balanced ion rejection. These nanoporous structures allow for simultaneously high water flux and ion rejection, presenting edge charge as a new paradigm for designing efficient desalination membranes. In contrast, hydrogen-functionalized nitrogen-terminated nanopores offer 100% rejection of boron, a difficult-to-remove neutral contaminant found in seawater, due to positive edge charges, which although compromise anion rejection, repel boric acid molecules with positively charged termini. Overall, our work provides rich insights into water and ion transport via realistic functionalized nanopores and demonstrates new charge-mediated pathways for highly selective ionic and molecular rejection.