Due to their high catalytic activity, stability and low cost, nanozymes with oxidase-like activity have attracted widespread interest in the fields of analytical detection and colorimetric sensing. To further promote the catalytic activity and the sensitivity of dopamine (DA) sensing, herein, a mixed valence Ce-MOF (MVCM) with enhanced oxidase-like activity was synthesized by the dielectric barrier discharge (DBD) microplasma method. Compared with hydrothermal synthesis, the prepared MVCM synthesized using a microplasma showed a higher catalytic activity, which benefits from a low Ce³⁺/Ce⁴⁺ ratio. Due to the spontaneous redox properties of Ce³⁺/Ce⁴⁺ in a MVCM, the MVCM-based colorimetric sensing of dopamine was established and showed a limit of detection of 0.74 μM over a linear range of 5–100 μM with high selectivity and stability and has been applied for the detection of dopamine in sweat. The proposed study provides an effective synthesis method for nanozymes with enhanced activity and shows great promise in widespread analytical and sensing applications.