Modifying polyamide layer via coupling reactions of dendrimer and polyphenol to maximize desalination performance

High-performance polyamide (PA) reverse osmosis membranes with enhanced water permeability and water-NaCl permselectivity are crucial for cost-effective and energy-efficient desalination. This study introduces a dual-step design strategy combining conventional interfacial polymerization (IP) with diazotization-coupling reactions to optimize membrane performance. By chemically grafting dendrimers and polyphenols onto nascent PA nanofilms, we engineered a composite desalination layer with reduced mass density (from 1.09 ± 0.013 g cm −3 to 1.22 ± 0.049 g cm −3 ) and increased porosity. Structural analysis reveals that thicker nanofilms exhibit lower densities due to dendrimer-induced nanovoid formation. The optimized membrane (G4D-tannic acid composite) achieves a water flux of 96.7 kg m −2  h −1 and more than 99 % NaCl rejection, surpassing both the original IP membrane and commercial benchmarks. These results demonstrate that covalent modification of PA layers through tailored coupling reactions can simultaneously enhance permeability and selectivity, advancing the design of next-generation desalination membranes.