A novel fluorescent sensor for highly sensitive detection of ascorbic acid in food based on inhibiting phosphatase-like activity of Zr-based MOF

Nanozyme-based sensors for detecting ascorbic acid (AA) generally depend on the reducibility of the analyte. However, these sensors are susceptible to interference from reducing substances in food. Herein, a novel fluorescent sensor for AA detection was developed based on inhibiting the phosphatase-like activity of a Zr-based metal-organic framework (Zr-CAU-28). Hydroxyl-rich AA molecules adsorb on the surface of Zr-CAU-28 through hydrogen bonding with [Zr₆O₄(OH)₄] cluster, leading to a decrease in the relative content of terminal hydroxyl groups within the catalytic sites. The constructed sensor exhibits a wide detection range (0.08-11 μg·mL^-1) and low detection limit of 0.025 μg·mL^-1. Potential interfering studies demonstrated the good selectivity of the sensor. Moreover, the fluorescent sensor can effectively detect AA in juices and vitamin C tablets, with the recovery rate ranging from 96.25 % to 108.50 %. This work represents the first application of phosphatase mimics for AA detection, offering a new strategy for food analysis.