Bimetallic Valence Modulation Strategy Boosted Peroxidase-/Laccase-like Activity of a MoCu-2MI MOF Nanozyme for Portable-Device-Enabled Trimodal Sensing of D-Penicillamine and Colorimetric Analysis of Phenolic Pollutants

Rational design of high-performance nanozymes with multiple enzyme-mimicking activities for biochemical sensing is one of the most promising directions in this area. D-PA is a kind of S-containing pharmaceutical for treating various diseases; the side effects caused by its unreasonable intake/residual have posed severe threats to human health and the living environment, making its accurate analysis gradually significant. However, most previous works exhibited the drawbacks of complicated synthesis of nanomaterials, unreliable single-modal results, and limited portable sensing ability. Herein, we prepared a low-cost MoCu-2MI MOF nanozyme via a simple hydrothermal method and revealed its excellent peroxidase/laccase dual-enzyme-mimicking properties that might benefit from a bimetallic valence modulation strategy via multifaceted experiments (EIS, EPR, ROS probes, and Michaelis-kinetic tests). Initially, MoCu-2MI MOF worked as a POD mimic and catalyzed the oxidation of TMB into blue-colored Ox-TMB. By synergistically harnessing the visual/photothermal effect of Ox-TMB and the effective reduction and ROS-scavenging abilities of D-PA, we constructed the first colorimetric-RGB-photothermal trimodal D-PA sensor with the assistance of portable devices, bringing evidently strengthened cost-effectiveness, reliability, and portable sensing ability. The LODs for D-PA under the three modes were 0.24, 7.88, and 7.98 μM, which could compete with most previous works. Moreover, the trimodal sensor presented satisfactory applicability in human serum and milk samples. More surprisingly, taking 2,4-DP as the model target (LOD = 0.11 μM), we further achieved the visual analysis of phenolic pollutants based on the excellent LAC-like activity of MoCu-2MI MOF. This work not only offered an effective approach for the exploration and controllable modulation of nanozymes with multiple enzyme-like properties but also opened up unique horizons for the design of multimodal portable biosensors.