Synthesis And Characterization Of Functional Zirconium Oxygen Clusters And Their Catalytic Degradation Properties For Organophosphate Esters

At present,nerve agents are widely used on the battlefield,which not only pose a serious threat to human safety but also cause pollution to the environment.Therefore,it is important to develop non-polluting and effective catalytic degradation materials for nerve agents to maintain social security.Nature’s phosphotriesterase（PTE）contains the active site,Zn（II）-OH-Zn（II）,which can catalyze the degradation of neurotoxic agents.In this paper,Zr₆（OH）₄O₄（OMc）₁₂ zirconium oxygen cluster containing Zr-OH-Zr catalytic sites with similar phosphotriesterase activity were selected and used with o-halogen benzoic acid（o-fluorobenzoic acid,o-chlorobenzoic acid,o-bromobenz oic acid and o-iodobenzoic acid）and aminobenzoic acid（m-aminoben zoic acid and p-aminobenzoic acid）,which are favorable for the catalytic degradation of nerve agents,respectively for modification.Zirconium oxygen clusters modified with o-halogenated benzoic acid and m/p-aminobenzoic acid were prepared,the structures were characterized by various characterization methods,and the degradation performance of the two types of materials against the nerve agent simulant DMNP and the nerve agent GD was systematically investigated,with the following results.（1）In this paper,a new class of Zr oxocluster degradation materials were prepared by reacting o-halogenated benzoic acids（o-fluorobenzoic acid,o-chlorobenzoic acid,o-bromobenzoic acid and o-iodobenzoic acid）with Zr₆（OH）₄O₄（OMc）₁₂ containing a PTE-like structure.Preparation of a new class of Zr oxocluster degradation materials,X-Zr cluster（X=F,Cl,Br,I）.The structure and stability of the prepared materials were characterized by single-crystal X-ray diffraction,IR,PXRD and thermogravimetry,the results demonstrated the successful synthesis of F-Zr cluster,Cl-Zr cluster,Br-Zr cluster,and I-Zr cluster.The performance of four materials for catalytic degradation of the nerve agent GD and its simulant DMNP was systematically investigated.The experimental results showed that the catalytic degradation of DMNP（2μL,p H=10）by 8 mg catalyst at room temperature showed that the activity of the catalysts was I-Zr cluster>Cl-Zr cluster>Br-Zr cluster>F-Zr cluster.90.0%of DMNP degradation was achieved after 180 min of catalytic reaction by I-Zr cluster.The degradation of DMNP by X-Zr cluster（X=F,Cl,Br,I）was in accordance with the primary kinetics,and the half-life and kinetic constants of I-Zr cluster were 14.0 min and 0.050 min^-1 respectively.The catalytic degradation of GD（4μL）was carried out under 1 m L of N-ethylmorpholine buffer solution（p H=8）and 8 mg of catalyst.The catalyst activities were I-Zr cluster>Cl-Zr cluster>Br-Zr cluster>F-Zr cluster,where 100%conversion of GD was achieved at 60 min and 30 min of reaction for Cl-Zr cluster and I-Zr cluster catalytic degradation of GD,respectively.The degradation of GD by X-Zr cluster（X=F,Cl,Br,I）was in accordance with the secondary kinetics,and the kinetic constants and half-lives of I-Zr cluster were 30.1L/（mmol×min）and 1.5 min.The degradation of GD by X-Zr cluster（X=F,Cl,Br,I）under the same conditions was better than that of Zr₆（OH）₄O₄（OMc）₁₂（76.9%of GD degradation at 90 min）.The degradation product study of the simulant DMNP showed that the catalyst catalyzed the hydrolysis reaction of DMNP and the P-O bond broke to produce non-toxic dimethyl phosphate and p-nitrophenol,and the I-Zr cluster was still catalytically active against DMNP after four repeated uses,which is a good material with catalytic degradation performance against the nerve agent.（2）The amino-modified Zr oxocluster materials,m-NH₂-Zr cluster and p-NH₂-Zr cluster were obtained by reacting m-aminobenzoic acid and p-aminobenzoic acid with Zr₆（OH）₄O₄（OMc）₁₂,respectively,using the ligand exchange method,and were characterized by IR,thermogravimetric analysis,CHN elemental analysis and ¹³C NMR,and the results showed that the amino benzoic acid successfully coordinated with Zr.In this paper,the degradation performance of m-NH₂-Zr cluster and p-NH₂-Zr cluster on the nerve agent simulant DMNP and nerve agent GD was systematically investigated.The results showed that the degradation activity of the catalysts was m-NH₂-Zr cluster>p-NH₂-Zr cluster at room temperature,catalyst dosage of 5 mg,and 2μL DMNP（p H=10）in the reaction system.The degradation of DMNP catalyzed by m-NH₂-Zr cluster reached 76.6%after 90 min.The degradation process of DMNP by m-NH₂-Zr cluster and p-NH₂-Zr cluster were in accordance with the primary kinetics,and the m-NH₂-Zr cluster degraded DMNP with the shortest half-life and kinetic constants of 12.9 min and 0.054min^-1.The catalytic activity of 5 mg catalyst for the degradation of 4μL GD at p H=8 was m-NH₂-Zr cluster<p-NH₂-Zr cluster,and the degradation rates of m-NH₂-Zr cluster and p-NH₂-Zr cluster to GD after 90 min of reaction were98.0%and 100%,respectively.The degradation of GD by the catalyst was in accordance with the secondary kinetics,and the kinetic constants and half-lives of the p-NH₂-Zr cluster were 12.4 L/（mmol×min）and 3.6 min.The degradation performance of m-NH₂-Zr cluster and p-NH₂-Zr cluster for both DMNP and GD under the same conditions was better than that of the Zr₆（OH）₄O₄（OMc）₁₂ material（49.2%for DMNP and 69.7%for GD at 90 min of reaction）.In this paper,the degradation products of DMNP were analyzed,and non-toxic dimethyl phosphate was detected in the degradation system of DMNP,which proved that DMNP underwent hydrolysis reaction during the reaction process,and the m-NH₂-Zr cluster was still catalytically active after four cycles,thus m-NH₂-Zr cluster and p-NH₂-Zr cluster are a good material for nerve agent degradation.