Rapidly and ultra-sensitive colorimetric detection of H₂O₂ and glucose based on ferrous-metal organic framework with enhanced peroxidase-mimicking activity

In this article, a novel metal-organic framework, namely MIL-101(Fe-II), was firstly synthesized via a facile method. In the presence of H2O2, MIL-101(Fe-II) possesses excellent peroxidase-like activity toward the classical chromogenic substrate, N,N-Diethyl-p-phenylenediamine sulfate salt (DPD). The substitution of Fe2+ enhances the construction of Fe(II)-oxo nodes and accelerates electrons transfer between DPD and H2O2, thereby improving the peroxidase-mimicking catalytic activity of MIL-101(Fe-II) nanoenzyme. Additionally, DPD molecules could be adsorbed readily onto the surface of the nanoparticles due to the pi-pi interaction. The study of Michaelis constant indicates that the MIL-101(Fe-II) exhibits a higher affinity towards DPD (0.16 mM) in contrast to horseradish peroxidase (0.78 mM). In view of the impressive catalytic performance of MIL-101(Fe-II), two reliable monitoring platforms for the rapid detection of H2O2 and glucose were established with extremely low detection limits of 18.04 nM and 0.87 mu M in the ranges of 40-5000 nM and 1.2-300 mu M, respectively. The study of the catalytic mechanism indicates that DPD oxidation is attributed to the hydroxyl radical (center dot OH) produced from the decomposition of H2O2 catalyzed by MIL-101(Fe-II). Furthermore, the developed sensor indicates high selectivity and stability and can be effectively appropriate for the detection of H2O2 and glucose in real samples. This work not only provides a novel nanozyme with superior catalytic performance for biological analysis, but also broadens the application field of MIL-101(Fe-II) material.