To improve the peroxidase-like activities of metal–organic frameworks (MOFs) as nanozymes, a ternary MIL-100(Fe)@PMo₁₂@3DGO nanocomposite was designed and fabricated by encapsulating Keggin-type H₃PMo₁₂O₄₀ (PMo₁₂) with fast and reversible multi-electron redox processes and an electron-rich structure into MIL-100(Fe), then being covered by three-dimensional graphene (3DGO) with higher conductivity, larger surface area, higher porosity, and better chemical stability. As a consequence, the as-prepared MIL-100(Fe)@PMo₁₂@3DGO nanocomposite exhibits excellent peroxidase-like activities, namely, the lowest limit of detection (0.14 μM) in the range of 1–100 μM for glucose to date, to the best of our knowledge, attributed to the individual and synergistic effects of H₃PMo₁₂O₄₀, 3DGO and MIL-100(Fe).