Ligand-Defect Modulation of UiO-66(Ce) Unlocks Oxygen-Vacancy-Driven Glyphosate Hydrolysis and Sensitive Detection

A biomimetic dual-function nanozyme based on a cerium-based metal-organic framework (UiO-66(Ce)-3) with engineered oxygen vacancies was developed for efficient hydrolysis and sensitive detection of glyphosate. Acetic acid-triggered "missing-linker" defects partially disrupted the Ce-O coordination environment, generating oxygen vacancies and exposing Ce³⁺/Ce⁴⁺ redox sites. The Ce⁴⁺ centers polarize the phosphate bond, while the adjacent Ce³⁺ sites facilitate the nucleophilic cleavage of the C-P bond. Under alkaline conditions, UiO-66(Ce)-3 showed excellent organophosphorus hydrolase-like activity with a k_cat of 57.77 s^-1, an SA of 0.70 U·mg^-1, and a k_cat/K_m of 152.04 × 10³ M^-1 s^-1. The nanozyme effectively mitigated the glyphosate-induced toxicity in plants with a survival rate of 95%. Furthermore, the oxygen vacancies endowed pH-switch enzyme-like activity. With the pH at 4.0, UiO-66(Ce)-3 showed oxidase-like activity, which could realize high-sensitivity detection of glyphosate via point-of-care testing (LOD of 11.66 ng·mL^-1) with good stability and reusability. And it showed a good recovery of 93.51%-110.19% in complex matrices, validation against the HPLC. The prepared pH-switchable nanozyme provides a novel approach to the detection and degradation of organophosphorus compounds.