In recent years, Zr-based metal-organic frameworks (MOFs) have been developed that facilitate catalytic degradation of toxic organophosphate agents, such as chemical warfare agents (CWAs). Because of strict regulations, experiments using live agents are not possible for most laboratories and, as a result, simulants are used in the majority of cases. Reports that employ real CWAs are scarce and do not cover the whole spectrum of agents. We here present a comparative study in which UiO-66-NH, NU-1000, MOF-808, and PCN-777 are evaluated for their effectiveness in the degradation of paraoxon and the chemical warfare agents tabun, VX, and soman, in N-ethylmorpholine buffer (pH 10) as well as in pure water. All MOFs showed excellent ability to degrade the agents under basic conditions. It was further disclosed that tabun is degraded by different mechanisms depending on the conditions. The presence of an amine, either as part of the MOF structure (UiO-66-NH) or in the agent itself (VX, tabun), is the most important factor governing degradation rates in water. The results show that MOFs have great potential in future protective applications. Although the use of simulants provides valuable information for initial screening and selection of new MOFs, the use of live agents revealed additional mechanisms that should aid the future development of even better catalysts.

Nerve agents are among the most toxic substances known to man. Recent events in Syria, Malaysia, and the UK illustrate that the threat of these substances is real and actual. The timely detection and identification of nerve agents is of great importance to facilitate timely decontamination or medical countermeasures. In this work, an effective and sensitive detection system, based on the metal−organic framework (MOF) NU-1000, was developed for the disclosure of V-agents, a class of nerve agents that is very persistent, highly toxic, and difficult to detect. NU-1000 is a zirconium-based MOF that can hydrolyze VX into a nontoxic phosphonic acid and the thiol 2-(diisopropylamino)ethanethiol. In this work, it was hypothesized that the four noncoordinating sites that are present on each Zr-building brick of this MOF could be functionalized with the two carboxylates present in 5,5′-di-thio-bis(2-nitrobenzoic acid), DTNB. This dimeric (RS-SR) compound efficiently reacts with thiols by S−S bond exchange and results in the release of the chromophore RS-H. Thus, the target hybrid material (DTNB@ NU-1000) was expected to degrade VX and at the same time give a visual color response upon reaction of the thiol-containing degradation product of VX with MOF-bound DTNB. We here report that DTNB@NU-1000 can be readily synthesized and that it is surprisingly active in the degradation of VX in neutral buffer. Moreover, the degradation of VX resulted in a color response, the intensity of which showed linear correlation with the VX concentration used. The applicability of this material was illustrated by a proof-of-concept detection kit for VX-contaminated surfaces, as exemplified with VX-contaminated metal panels coated with military paint [chemical agent resistant coating]. This procedure requires minimal training burden, and VX contamination down to a level of about 1−2 μg/cm 2 could be reliably visually established, during a total handling time of 20 min.

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Novichoks are a novel class of nerve agents (also referred to as the A-series) that were employed in several poisonings over the last few years. This calls for the development of novel countermeasures that can be applied in protective concepts (e.g., protective clothing) or in decontamination methods. The Zr metal−organic framework MOF-808 has recently emerged as a promising catalyst in the hydrolysis of the V-and G-series of nerve agents as well as their simulants. In this paper, we report a detailed study of the degradation of three Novichok agents by MOF-808 in buffers with varying pH. MOF-808 is revealed to be a highly efficient and regenerable catalyst for Novichok agent hydrolysis under basic conditions. In contrast to the V-and G-series of agents, degradation of Novichoks is demonstrated to proceed in two consecutive hydrolysis steps. Initial extremely rapid P−F bond breaking is followed by MOF-catalyzed removal of the amidine group from the intermediate product. The intermediate thus acted as a competitive substrate that was rate-determining for the whole two-step degradation route. Under acidic conditions, the amidine group in Novichok A-230 is more rapidly hydrolyzed than the P− F bond, giving rise to another moderately toxic intermediate. This intermediate could in turn be efficiently hydrolyzed by MOF-808 under basic conditions. These experimental observations were corroborated by density functional theory calculations to shed light on molecular mechanisms.