Supramolecular nanocrystalline membranes with well-aligned subnanochannels for enhanced reverse osmosis desalination

Thin-film composite membranes are integral to the reverse osmosis (RO) process, effectively converting seawater and brackish water into potable water. While significant strides have been made in improving water permeability and salt rejection, there has been a corresponding lag in enhancing chlorine resistance and boron rejection. This study presents a suprasmolecular nanocrystalline membrane (SNM) with abundant subnanometer channels created through precisely assembled and well-oriented tetra-oligomer chains, enhanced by interfacial hydrogen bonding under nanoconfined space. The 6 nm-thick SNM exhibits highly aligned nanocrystalline domains and a Young's modulus of 4 ± 0.5 GPa. Benefiting from its ultrathin thickness and well-oriented subnanoscale channels, the SNM functions effectively as a permeation and selective layer, achieving 99.6% NaCl rejection at 55 bar with a 3.5 wt% NaCl feed and delivering 2-4 times higher water permeance than commercial seawater RO membranes. Molecular dynamics simulations reveal that the abundant, well-aligned subnanochannels facilitate rapid water transport while raising the energy barrier for sodium ion transport. Furthermore, the SNM shows superior boron rejection (exceeding 92.5% at pH 7), remarkable chlorine resistance (200 ppm NaClO exposure for 300 hours), and sustained operational stability under extreme pH conditions (1 and 13) for over 168 hours. These findings establish that space-confined interfacial hydrogen bonding governs the precision self-assembly of robust subnanochannels, offering a new paradigm for high-resilience desalination membranes.