Ligand Engineering Enhances the Phosphatase Property of Zr-MOF Nanocrystals as Regulators to Alleviate Plants...

This work establishes a structure-activity relationship to enhance the phosphatase activity of MOF nanozymes and demonstrates a method to alleviate phosphorus deficiency stress in plants. Specifically, ligand engineering was centered on enhancing Lewis acidity to improve the phosphatase property of the Zr-MOF nanocrystals (NCs). The approach focused on constructing appropriate electron delocalization by increasing the electronegativity of the ortho-substituents on the ligands, resulting in a Lewis acidity of 784 µmol·g^-1. Among them, Zr(F)-MOF NCs exhibited a K_m of 0.095 mM, a K_cat of 0.137 s^-1, and a specific activity of 10.74 U·mg^-1. Theoretical calculations and in situ characterization revealed the mechanism by which ligand engineering enhances substrate adsorption and atomic orbital interactions in Zr-MOF NCs. The catalytic ability of Zr(F)-MOF NCs toward phosphorus-containing organic substrates in soil effectively mitigated Pi-deficiency stress, improving root development, leaf phenotype and photosynthetic performance. The root growth and biomass of phosphorus-deficient Arabidopsis and mung bean were restored to > 70% and > 79% of normal levels, respectively. Metabolomics analysis further revealed the nanozyme-mediated stress-resistance pathways, including organic acid secretion, antioxidant release, and sugar phosphate synthesis related to defense and signal transduction. Overall, this work provides a systematic nanotechnology-based methodology for addressing Pi stress in plants.