Hydrogen peroxide (H₂O₂) is an important oxidizing agent that plays a crucial role in the food and beverage industry, the pharmaceutical industry, environmental fields amongst others. However, as a by-product of metabolic oxidation processes, it poses an immediate danger to life and health when concentrations are beyond the minimum threshold limit of 75 ppm. The detection of H₂O₂ is therefore of prime importance. Herein, a simple colorimetric assay for the detection of H₂O₂ based on the peroxidase-like mimetic activity of Fe₃O₄@MIL-100(Fe)-Au nanozyme was established. The triad-component nanozyme was synthesized by growing a five-layer MIL-100(Fe) metal-organic framework(MOF) around the magnetic Fe₃O₄ nanorod core and finally deposited gold on the core-shell structure. The oxidation of colorless 3,3,5,5 - tetramethylbenzidine to blue by H₂O₂ is very slow. The addition of the nanozyme increases the oxidation process. The magnetic property of the nanozyme was further harnessed to enhance the oxidation process on a magnetic field. The versatility of the as-prepared Fe₃O₄@MIL-100(Fe)-Au was demonstrated by applying it for the catalytic degradation 4-nitrophenol. The magnetic property was subsequently harnessed to enhance the catalytic degradation of the organic pollutant and also to conveniently effect separation of the catalyst after application. Besides the catalysis, the magnetic property of the composite was utilized to enhance the adsorption of bacteria pathogen. We believe such magnetic MOF-based composites have potential applications in many fields including microreactor systems.