Two-Site Enhanced Porphyrinic Metal-Organic Framework Nanozymes and Nano-/Bioenzyme Confined Catalysis for Colorimetric/Chemiluminescent Dual-Mode Visual Biosensing.

The rational design of efficient nanozymes and the immobilization of enzymes are of great significance for the construction of high-performance biosensors based on nano-/bioenzyme catalytic systems. Herein, a novel V-TCPP(Fe) metal-organic framework nanozyme with a two-dimensional nanosheet morphology is rationally designed by using V2CTx MXene as a metal source and iron tetrakis(4-carboxyphenyl)porphine (FeTCPP) ligand as an organic linker. It exhibits enhanced peroxidase- and catalase-like activities and luminol-H2O2 chemiluminescent (CL) behavior. Based on the experimental and theoretical results, these excellent enzyme-like activities are derived from the two-site synergistic effect between V nodes and FeTCPP ligands in V-TCPP(Fe). Furthermore, a confined catalytic system is developed by zeolitic imidazole framework (ZIF) coencapsulation of the V-TCPP(Fe) nanozyme and bioenzyme. Using the acetylcholinesterase (AChE) as a model, our constructed V-TCPP(Fe)/AChE@ZIF confined catalytic system was successfully used for the colorimetric/CL dual-mode visual biosensing of organophosphorus pesticides. This work is expected to provide new insights into the design of efficient nanozymes and confined catalytic systems, encouraging applications in catalysis and biosensing.