Construction of protein-based separation membranes with tunable structure and performance through protein co-assembly

Proteins have emerged as promising materials to fabricate advanced separation membranes due to natural abundance, high biocompatibility, and precisely defined molecular structures. However, existing studies have primarily focused on enhancing membrane performance using proteins, with limited investigation into the mechanism of membrane-formation and structure-performance relationship of protein-based membranes. In this study, lysozyme (Lyz) and hemoglobin (BHb) were co-assembled to construct defect-free, tunable nanofiltration membranes with sub-10 nm pore sizes. The assembly behaviors in solutions, on solid substrates and on porous substrates were investigated. It is demonstrated that the membrane formation is predominantly governed by interface-induced planar growth of protein assembled nanofilms. The BHb electrostatically interacts with Lyz to tailor the pore structure of the protein assembled nanofilm, ultimately leading to the formation of programmable Lyz/BHb membranes. Furthermore, systematic optimization of key parameters including protein concentration and pH enables precise control over structure and performance of membranes. The protein membrane without defects and nanoparticles could be created by protein co-assembly with short time and multi-layer growth. The resulting Lyz/BHb membranes exhibit exceptional tunability in nanometer, with pore sizes at 1.4–6.0 nm and water permeance varying from 39 to 310 L⸱m −2 ⸱h −1 ⸱bar −1 . These protein-based membranes demonstrate high efficiency in diverse separation tasks, including protein retention, dye recovery, and antibiotic removal. This work provides a versatile and simple method for tailoring properties of protein-based membranes, offering promising opportunities for the development of customized separation membranes for various industrial and environmental applications.