A covalent organic framework–MnO2 nanosheet system for determination of glutathione

Covalent organic frameworks (COFs) are usually synthesized by virtue of Schiff base reaction between amino and aldehyde groups. Owing to their electron-rich property, COFs are widely applied to detect electron-deficient nitroaromatic explosives through photoinduced electron transfer mechanism. However, except for these cases, the COFs-based chemosensors are rarely reported for the analysis of electron-rich biomolecules. In this work, a fluorescent platform constructed by COFs and MnO2 nanosheets is developed for sensitive detection of glutathione (GSH). It is found that the fluorescence of COFs can be effectively quenched by MnO2 nanosheets. The quenching mechanisms involving inner filter effect and static quenching effect are discussed in detail. Due to the reducing ability of GSH, it can trigger the reduction of MnO2 to Mn2+, accompanying with the fluorescence recovery of COFs. The linear range of GSH is achieved from 0.5 to 100 µM with a detection limit of 0.28 µM. This method is further applied for GSH detection in human serum samples with satisfactory results.