Decontamination of neutral aqueous systems containing organophosphate esters by zirconium-based metal organic frameworks with or without amino groups

The usage of organophosphate esters as pesticides or nerve agents in chemical warfare caused vital environmental and safety issues. Although metal organic frameworks (MOFs) are often applied to remove the organophosphate esters by adsorption and catalytic degradation, a basic environment with N -ethylmorpholine buffer is essential. In this study, four kinds of zirconium-based MOFs (Zr-MOFs), labeled UiO-66, UiO-67, UiO-67-NH 2 , and UiO-67-2NH 2 , were prepared by the solvothermal method to decontaminate aqueous solutions containing organophosphate esters of paraoxon (POX) and sarin (a nerve agent) without adding any additional basic buffer. Effects of MOF/POX mass ratio and temperature on degradation kinetics and efficiency were investigated in detail. A possible mechanism for the POX decontamination by Zr-MOFs was proposed and verified. Results showed that the POX decontamination catalyzed by Zr-MOFs was a pseudo-first-order reaction. The introduction of amino groups in Zr-MOFs could increase the decontamination rate, which follows the order of “UiO-67-2NH 2 > UiO-67-NH 2 > UiO-67 > UiO-66”. The half-lives of POX and sarin with UiO-67-2NH 2 were 18 min and 5 min respectively, and more than 90% POX and 99% sarin could be decontaminated at room temperature. Compared with previous similar studies on POX degradation in N -ethylmorpholine buffer, UiO-67-2 N H 2 performs significantly better in terms of catalytic efficiency and environment. This work would broaden the application scope for the decontamination of aqueous solutions containing organophosphate esters under mild conditions, and offer an effective approach for the treatment of chemical warfare agents in modern society. Four types of Zr-MOFs prepared with different organic ligands by the solvothermal method can decontaminate POX into p -nitrophenol and diethyl phosphate in a neutral aqueous solution, and the activation energy (Ea) of UiO-67-2NH 2 is much lower than those of UiO-67-NH 2 , UiO-67, and UiO-66. • Zirconium-based metal organic frameworks (Zr-MOFs) were modified with amino groups. • The introduction of amino groups in Zr-MOFs could improve paraoxon decontamination. • Mechanism of POX degradation catalyzed by Zr-MOFs was proposed and verified. • More than 90% paraoxon can be degraded by Zr-MOFs in neutral aqueous solution. • Zr-MOF with two amino groups could remove >99% of sarin with a t 1/2 of 5 min.