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

Abstract

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-NH2, and UiO-67-2NH2, 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-67-2NH2 > UiO-67-NH2 > UiO-67 > UiO-66”. The half-lives of POX and sarin with UiO-67-2NH2 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-67-2NH2 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.