Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain
the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in
Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles
and JavaScript.
Large single crystals of charged 2D polymers are synthesized on a water surface, under kinetic control, by the irreversible Katritzky reaction. The crystals can act as an anion-selective membrane for osmotic energy generation.