Biomimetic Liquid-Sieving through Covalent Molecular Meshes

The porin pores of biological cell membranes enable molecules to be sieved out selectively while water molecules traverse the channel in a single file. Imitating this streaming mechanism is a promising way to create artificial liquid-sieving membranes, but ultrathin molecular pores need to be produced in a large membrane format to be functional under high transmembrane pressures. Here we show that a membrane composed of a covalent molecular mesh can filter mixtures of small molecules in a liquid by the porin-like mechanism. Tetrahedral network formers are polymerized layer-by-layer on a nanoporous substrate to yield a thin layer of a covalent molecular network containing an array of molecular meshes grown by a pore-limited mechanism. Each of the meshes exhibits high water permeability, estimated to be greater than 2500 Lm^-2 h^-1. Glucose or larger molecules are selectively sieved out while the solvent and solutes smaller than glucose traverse the mesh.