Peroxidase-like Active Cu-MOFs Nanozymes for Colorimetric Detection of Total Antioxidant Capacity in Fruits and Vegetables

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In this study, two types of Cu-MOFs (Cu-TCPP and CuO-TCPP) with a two-dimensional layered porous structure were prepared via in situ polymerization using Cu2+, CuO, and TCPP as raw materials. Both Cu-MOFs exhibited peroxidase-like activity, capable of catalyzing the oxidation of TMB by H2O2 to form oxTMB, resulting in an absorption peak at 652 nm and a color change from colorless to blue. Subsequently, the addition of AA can reduce oxTMB back to TMB, causing the color of the system to lighten or become colorless. Based on this principle, a simple and rapid colorimetric method for AA detection was established and successfully applied to the detection of TAC in fruits and vegetables. The results showed that Cu-TCPP and CuO-TCPP had a large linear range of ascorbic acid detection of 0.01–100 mM (Cu-TCPP) and 0.05–100 mM (CuO-TCPP). This study not only provides a novel method for preparing nanozymes with peroxidase-like activity, but also offers a simple approach for analyzing the TAC of food.