Water purification by membranes is widely investigated to address concerns related to the scarcity of clean water. Achieving high flux and rejection simultaneously is a difficult challenge using such membranes because these properties are mutually exclusive in common artificial membranes. Nature has developed a method for this task involving water-channel membrane proteins known as aquaporins. Here, the design and fabrication of graphene oxide (GO)-based membranes with a surface-tethered peptide motif designed to mimic the water-selective filter of natural aquaporins is reported. The short RF8 (RFRFRFRF, where R and F represent arginine and phenylalanine, respectively) octapeptide is a concentrated form of the core component of the Ar/R (aromatic/arginine) water-selective filter in aquaporin. The resulting GO-RF8 shows superior flux and high rejection similar to natural aquaporins. Molecular dynamics simulation reveal the unique configuration of RF8 peptides and the transport of water in GO-RF8 membranes, supporting that RF8 effectively emulates the core function of aquaporins.

Aquaporins (AQPs), the natural water channel, have been actively investigated for overcoming the limitations of conventional desalination membranes. An AQP-based biomimetic high-pressure desalination membrane is designed by tethering AQP-carrying red blood cell membrane (RBCM) vesicles onto graphene oxide (GO). RBCMs with AQPs are incorporated into GO based on the molecular recognition between the integrin of RBCM and Arginine-Glycine-Aspartate (RGD) ligand on the GO surface. GO is pre-functionalized with the Glycine-Arginine-Glycine-Aspartate-Serine peptide to capture RBCMs. RBCMs are inserted between GO flakes through the material-specific interaction between integrin of RBCM and RGD ligand, thus ensuring sufficient coverage of channels/defects in the GO for the full functioning of the AQPs. The incorporated AQPs are not completely fixed at the GO, as tethering is mediated by the integrin-RGD pair, and suitable AQP flexibility for appropriate functioning is guaranteed without frictional hindrance from the solid substrate. The integrity of the GO-RBCMs binding can provide mechanical strength for enduring high-pressure reverse-osmosis conditions for treating large amounts of water. This biomimetic membrane exhibits 99.1% NaCl rejection and a water permeance of 7.83 L m −2 h −1 bar −1 at 8 bar with a 1000-ppm NaCl feed solution, which surpasses the upper-bound line of current state-of-the-art membranes.