FeMo integrated covalent organic frameworks: Peroxidase-mimetic colorimetric biosensors for multivariate sensing hydrogen peroxide and ascorbic acid in serum and beverages.

An efficient and readable sensor is desirable for food safety and diagnosis. Herein, a homogeneous mimicking enzyme was constructed by encapsulating polyoxometalate (NH₄)₃[FeMo₆O₁₈(OH)₆]·6H₂O (FeMo) into the covalent organic framework (FeMo@COF). Coordinating the spatial confinement effect of COF, FeMo exhibited superior peroxide-like activity to catalyze HO to O• which achieved the "on-off" consecutive sensing of HO and AA via a readable colorimetric mode, with the limit of detection (LOD) at 30 μM and 0.35 μM, respectively. A convenient smartphone assistant platform was established and realized rapid, portable, visual monitoring of AA with LOD of 0.06 μM, and satisfied recoveries with 96.88-104.65 % in human serum and 98.37-107.61 % in commercial beverages. Furthermore, a logic gate circuit was designed to illustrate the potential utilization of combining the intelligent facilities with the experiment. This strategy provides efficient, swift, convenient sensor FeMo@COF with great potential contribution in food safety and diagnosis.