In Situ Domain-Confined CoIrO_<i>x</i> Clusters within MOFs: Efficient Artificial Nanozymes for Multimodal Sensing.

Abstract

Inadequate control over particle size and intermediate adsorption leads to low active site density and sluggish reaction kinetics, which remain critical challenges for the development of high-performance nanozymes. Here, we report a one-pot strategy that simultaneously enables IrO_<i>x</i> nucleation, metal organic framework (MOF) formation, and cobalt (Co) doping, thus constructing in situ confined Co-doped IrO_<i>x</i> (CoIrO_<i>x</i>) cluster complexes within MOFs (denoted as CoIrO_<i>x</i>/CoIr-MOFs). Systematic characterization revealed that MOF nanosheets grown on the preferentially nucleated CoIrO_<i>x</i> surface inhibit their excessive growth and aggregation, ultimately confining ultrafine CoIrO_<i>x</i> uniformly within the interlayer regions and forming tight interfaces. Moreover, Co doping into the IrO_<i>x</i> lattice weakens the adsorption energy of the OH* intermediates, thereby reducing the overpotential for oxygen reduction and the energy barrier of the rate-determining step. Concurrently, it enhances the substrate affinity of the catalytic sites. The as-prepared CoIrO_<i>x</i>/CoIr-MOFs can directly catalyze oxygen or hydrogen peroxide to generate reactive oxygen species (ROS), exhibiting multienzymes (oxidase, peroxidase, and laccase) like activities that enable different signal transduction. As a proof of concept for the rational design of the nanozyme, CoIrO_<i>x</i>/CoIr-MOFs constructed a triple-modal sensing platform. Its highly efficient detection performance for glutathione (GSH) stems from the excellent catalytic properties of CoIrO_<i>x</i>/CoIr-MOFs under the synergistic regulation of in situ confinement and Co doping. This work provides a foundational design strategy for metal oxide/MOF heterostructures with excellent catalytic performance and supports the further applications of advanced nanozyme in catalysis and biosensing.