Protein Nanosheet-Programmed Interfacial Polymerization for Heterogeneous Polyamide Desalination Membranes

Spatial regulation of monomer diffusion during interfacial polymerization (IP) is critical for engineering high-performance polyamide (PA) reverse osmosis membranes yet remains difficult to control with conventional nanomaterial additives. Here, we report a biomimetic diffusion-programming strategy using Mycobacterium smegmatis porin A (MspA) protein nanosheets (MNSs) as interfacial regulators. The MNSs integrate MspA nanochannels within a PB-PEO polymer matrix, coupling matrix-imposed diffusion restriction with channel-mediated rapid MPD transport. This protein-channel/polymer-matrix architecture creates spatially heterogeneous MPD diffusion pathways during IP, directing the formation of PA layers with elevated and leaf-like structures. The resulting heterogeneous PA architecture increases the water-accessible surface area and reduces local transport resistance, while maintaining selective-layer integrity and a high cross-linking degree. The optimized TFCM-0.26 membrane achieved a water permeance of 3.55 L m-2 h-1 bar-1, representing a 77.5% increase over the control TFC membrane, while maintaining excellent NaCl rejection above 99%. The membrane also exhibited stable salt-separation performance under varied salinity, pressure, and long-term operation. Mechanistic diffusion measurements and single-channel transport analyses confirmed that MspA nanochannels provide localized fast MPD transport within the diffusion-restrictive PB-PEO matrix. This work demonstrates that protein nanosheets can serve as programmable nanointerfacial regulators for directing PA formation, offering a biomimetic strategy to alleviate the permeability-selectivity trade-off in desalination membranes.