Three‐Channel Electron Engineered Fe‐88A@CeO 2 /CDs Nanozyme with Enhanced Oxidase‐Like Activity for Efficient Biomimetic Catalysis

Abstract Iron‐based metal‐organic framework (MOF) nanozymes have garnered considerable attention owing to a large specific surface area, adjustable porosity, large Fe‐O clusters, and unsaturated Fe sites. However, the sluggish charge‐transfer rate and restricted active sites of the nanozymes lead to poor enzyme‐like activity and further impede their biomimetic catalysis. Herein, a three‐channel electron‐engineered Fe‐88A@CeO 2 /carbon dots (Fe‐88A@CeO 2 /CDs) nanozyme is proposed for efficient biomimetic catalysis. Fe‐88A@CeO 2 /CDs nanozyme is prepared by incorporation of CeO 2 and CDs into the porosity of Fe‐88A. Specifically, the original Fe (II)/Fe (III) and the introduced Ce (III)/Ce (IV) redox couples of the nanozyme constitute a dual electron transfer channel. Furthermore, the presence of CDs produces another electron transfer channel. The three‐channel electron engineering strategy for nanozymes can accelerate the electron transfer process accompanied with more active sites, thereby greatly enhancing the oxidase‐like activity of Fe‐88A@CeO 2 /CDs for biomimetic catalysis. The nanozyme can efficiently convert oxygen to ·, oxidizing colorless 3,3′,5,5′‐tetramethylbenzidine (TMB) to blue ox‐TMB, and meanwhile the ox‐TMB effectively quenches the fluorescence of CDs. As proof of concept, the nanozyme is utilized to construct a colorimetric‐fluorescence bimodal immunosensor for monitoring Staphylococcal enterotoxin B with excellent performance. This work provides promising insight into designing excellent nanozymes for effective biomimetic catalysis in various fields.