Photoactivated Covalent Organic Frameworks as an Oxidase-like Nanozyme for the Ultrasensitive Detection of Glutathione

The advancement of nanozymes with oxidase-initiating activity that are affordable and stable is essential for real-time monitoring in biosensors, medicine, and environmental protection and remains a significant challenge. Covalent organic framework (COF) is an emerging type of crystalline porous organic framework material that is constructed from organic building units by covalent bonds. In this study, we successfully synthesized three isoreticular two-dimensional (2D) COFs by choosing diarylamino-benzene-based tetra-amines to construct [4 + 4]-type COFs. The resultant COFs exhibited excellent oxidase-mimicking activity under light stimulation, which can catalyze the oxidation of tetramethylbenzydine (TMB) by the formation of O2•– free radicals under an open-air condition. A sensitive sensor was designed based on the oxidase-mimicking activity of these COFs for the determination of glutathione (GSH) in real samples, achieving a detection limit of 0.22 μM, outperforming the standard materials studied in GSH detection within reticular frameworks. This work offers possibilities for investigating the oxidase-initiating activity of nanozymes and broadening the utilization of COFs in the realm of biosensing.