Bioinspired Fabrication of Two-Dimensional Metal–Organic Framework-Based Nanozyme for Sensitive Colorimetric Detection of Glutathione

Inspired by the ultrahigh reactivity of the Fe–N4 active site in natural enzyme horseradish peroxidase (HRP), this work designs and fabricates a two-dimensional (2D) metal–organic framework (MOF)-based nanozyme, 2D Cu-TCPP(Fe) MOFs, involving long-ordered arrangement of the Fe–N4 macrocyclic units. The framework has been constructed by the bridging coordination between Cu(II) ions and the peripheral carboxyl groups of a Fe(III) ion-centered metalloporphyrin TCPPFe. Taking H2O2 and 3,3′,5,5′-tetramethylbenzidine (TMB) as the substrates, the nanozyme shows an excellent activity toward H2O2 decomposition with a Michaelis constant (Km) of 2.67 mM smaller than that of HRP. The hydroxyl radical (·OH)-involved reaction mechanism has been verified experimentally, with the Fe–N4 moieties identified as the active sites. As a proof-of-concept application, the nanozyme-catalyzed TMB + H2O2 system is employed as a colorimetric assay for glutathione detection, which delivers two linear ranges of 0.1–10 and 10–60 μM, with a lower detection limit of 90.8 nM (S/N = 3). In the meantime, the satisfying peroxidase-like (POD-like) activity of 2D Cu-TCPP(Fe) MOFs holds great potential for wider biochemical and biomedical applications.