Colorimetric detection of hydrogen peroxide using metal-organic frameworks-based nanozymes

Hydrogen peroxide (H₂O₂) is an important intermediate in enzymatic glucose sensing systems and is widely used as an indicator for glucose determination in biomedical and healthcare applications. Nanozymes that mimic the activity of natural enzymes have attracted considerable attention as low-cost and highly stable alternatives to biological enzymes. In particular, peroxidase-like nanozymes are promising candidates for colorimetric H₂O₂ detection owing to their excellent catalytic stability and ease of preparation. In this study, metal-organic frameworks (MOF)-based composite nanozyme, MIL-CFO@SiO₂, was synthesized by integrating silica-coated cobalt ferrite (CoFe₂O₄, CFO) with a MIL-101(Fe) structure. A SiO₂ interlayer was introduced onto the CFO surface to enhance interfacial compatibility with the MOF and improve structural stability.

The synthesized composites were characterized using XRD, FT-IR, and SEM. The surface chemical properties and structural stability of MIL-CFO@SiO₂ were considered to contribute to the formation of highly active catalytic sites. The peroxidase-like activity of the composite was evaluated using SAT-3 (N,N'-Bis(2-hydroxy-3-sulfopropyl) tolidine, disodium salt tetrahydrate), as a chromogenic substrate in the presence of hydrogen peroxide (H₂O₂). MIL-CFO@SiO₂ effectively catalyzed the oxidation of SAT-3, resulting in a distinct color change. When applied to hydrogen peroxide detection, MIL-CFO@SiO₂ demonstrated higher peroxidase-like activity than MIL-101(Fe). These results suggest that the proposed composite is a promising nanozyme platform for simple and accurate colorimetric sensing and has applications in healthcare monitoring technology and early diagnosis of diabetes.