Mixed-valence Ce-Fe bimetallic MOFs with multi-enzyme-like activities for colorimetric biosensing and catalytic...

Metal-organic frameworks (MOFs) have emerged as highly sought-after artificial nanozymes due to the distinct crystalline, tailored structure, tunable composition. In this work, a one-step solvothermal method was adopted to synthesize a series of bimetallic MOFs (Ce_xFe_y-MOF) through the substitute of Fe into Ce-MIL-140A. Interestingly, with introducing Fe(_III) ions, MOFs crystal structure gradually changed from Ce-MIL-140A to Fe-MIL-88B. The resulted bimetallic Ce_xFe_y-MOF exhibited controllable multiple enzyme-like properties, including peroxidase-like (POD-like), oxidase-like (OXD-like) and phosphatase-like activities, which can be modulated by varying the Ce/Fe ratio. Specifically, Ce₅Fe₅-MOF displayed much more remarkable OXD-like and POD-like activities, while Ce₉Fe₁-MOF demonstrated high phosphatase-like activity. The reaction kinetics and potential influence factors of Ce₅Fe₅-MOF and Ce₉Fe₁-MOF were systematically investigated, demonstrating their high catalytic activity, outstanding durability and recyclability. Finally, Ce₅Fe₅-MOF were applied for detection of ascorbic acid (AA) and degradation of phenol with its OXD-like and POD-like activities, respectively. This work opens new insight into design of mixed mental MOFs as multiple nanozymes.