Ce-MOF with Intrinsic Haloperoxidase-Like Activity for Ratiometric Colorimetric Detection of Hydrogen Peroxide

Metal-organic framework (MOF) nanozymes, as emerging members of the nanozymes, have received more and more attention due to their composition and structural characteristics. In this work, we report that mixed-valence state Ce-MOF (MVCM) has intrinsic haloperoxidase-mimicking activity. MVCM was synthesized by partial oxidation method using Ce-MOF as a precursor. In the presence of H2O2 and Br-, MVCM can catalyze oxidative bromination of chromogenic substrate phenol red (PR) to produce the blue product bromophenol blue (Br4PR), showing good haloperoxidase-like activity. Because of the special chromogenic substrate, we constructed a ratiometric colorimetric-sensing platform by detecting the absorbance of the MVCM-(PR, Br-) system at wavelengths of 590 and 430, for quantifying H2O2, where the detection limit of the H2O2 is 3.25 mu M. In addition, the haloperoxidase-mimicking mechanism of the MVCM is proposed. Moreover, through enzyme kinetics monitoring, the K-m (H2O2 and NH4Br) of the MVCM is lower than that of cerium oxide nanomaterials, indicating that the MVCM has a stronger binding affinity for H2O2 and NH4Br than other materials. This work provides more application prospects for the development of nanozymes in the field of biosensors in the future.

Automated summary

In this study, mixed-valence state Ce-MOF (MVCM) nanozymes with intrinsic haloperoxidase-mimicking activity were synthesized and demonstrated good performance in catalyzing oxidative reactions. A ratiometric colorimetric-sensing platform was developed based on MVCM's capability to quantify H2O2 with a low detection limit. The proposed haloperoxidase-mimicking mechanism of MVCM and its stronger binding affinity for H2O2 and NH4Br compared to other materials provide new insights for the future development of nanozymes in biosensing applications.