Nanoarchitectonics of a covalent organic supramolecular cage (COSC) for fluorescent visual detection of macrolides

Macrolides, a major group of antibiotic pollutants, have been widely observed in water and sediments. For onsite identification of macrolides in water environments, we designed and synthesized a quadrangular prism-shaped covalent organic supramolecular cage (COSC) <i>via</i> an aldol-amine condensation. Multiple hydrogen bonding sites were introduced into the building blocks to increase host-guest interactions. Meanwhile, by introducing a stimuli-sensitive module, TPE, the fluorescence of the supramolecule changes upon encapsulation of the clarithromycin guest which was a type of macrolides. The cage structure was fully characterized using NMR and high-resolution ESI mass spectrometry. The fluorescence recognition process and detection limitations of the cage for clarithromycin were investigated using NMR, UV-vis, and fluorescence spectroscopy. This study expands the application of precisely designed covalent supramolecular cages for monitoring antibiotic-based environmental pollutants.