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.