UiO-66(Ce) Nanozymes with Dual-site Synergistic Catalysis for Efficient Hydrolysis of Organophosphorus Poisons

Abstract

Nanozymes are a class of nanomaterials capable of mimicking the activity of phosphatase, offering sustainable hydrolysis and efficient catalytic strategies to address environmental pollution caused by organophosphorus pesticides (OPs). However, challenges such as low activity and insufficient mechanistic understanding of nanozymes remained critical concerns. Herein, UiO-66(Ce) was synthesized and loaded onto polyvinylidene difluoride (PVDF) to obtain UiO-66(Ce)/PVDF for hydrolysis of p-nitrophenol phosphate (p-NPP), a simulant of OPs. The structure of UiO-66(Ce) contained three proton types, namely μ₃-OH, Ce-OH₂, and Ce-OH. It was shown that the catalytic activity originated from the defect site (Ce-OH₂/Ce-OH). Water molecules on the Ce-OH₂ site dissociated to produce OH^- during catalysis, which led to the formation of Ce-OH. The process was enhanced in alkaline environments. Interestingly, Ce-OH with different valences played distinct roles during hydrolysis of p-NPP. On this basis, OH^--assisted Ce(III)/Ce(IV)-OH dual-site synergistic catalytic mechanism was proposed: the Ce(IV)-OH site first coordinated with the phosphate group to reduce its electron density and activate the P-O bond, and then the Ce(III)-OH site attacked the P atom to realize the nucleophilic attack on the P-O bond. Finally, UiO-66(Ce)/PVDF was adhered to the impeller for hydrolysis of p-NPP, providing novel insights into removing p-NPP from water bodies.