Ultra-fast catalytic detoxification of organophosphates by nano-zeolitic imidazolate frameworks

Organophosphate Detoxification and Acetylcholinesterase Reactivation Triggered by Zeolitic Imidazolate Framework Structural Degradation

Organophosphate (OP) toxicity is related to inhibition of acetylcholinesterase (AChE) activity, which plays a key role in the neurotransmission process. In this work, we report the ability of different zinc zeolitic imidazolate frameworks (ZIFs) to behave as potential antidotes against OP poisoning. The Zn-L coordination bond (L = purine, benzimidazole, imidazole, or 2-methylimidazole) is sensitive to the G-type nerve agent model compounds diisopropylfluorophosphate (DIFP) and diisopropylchlorophosphate, leading to P-X (X = F or Cl) bond breakdown into nontoxic diisopropylphosphate. P-X hydrolysis is accompanied by ZIF structural degradation (Zn-imidazolate bond hydrolysis), with the concomitant release of the imidazolate linkers and zinc ions representing up to 95% of ZIF particle dissolution. The delivered imidazolate nucleophilic attack on the OP@AChE adduct gives rise to the recovery of AChE enzymatic function. P-X bond breakdown, ZIF structural degradation, and AChE reactivation are dependent on imidazolate linker nucleophilicity, framework topology, and particle size. The best performance is obtained for 20 nm nanoparticles (NPs) of Zn(2-methylimidazolate)2 (sod ZIF-8) exhibiting a DIFP degradation half-life of 2.6 min and full recovery of AChE activity within 1 h. 20 nm sod ZIF-8 NPs are not neurotoxic, as proven by in vitro neuroblastoma cell culture viability tests.

High Capacity Adsorption and Degradation of a Nerve Agent Simulant and a Pesticide by a Nickel Pyrazolate Metal-Organic Framework

The development of materials that enable the efficient removal of toxic compounds is important for the improvement of current protective materials or decontamination technologies. Current materials rely either on agent removal by adsorption or by effecting (catalytic) degradation. Ideally, both of these mechanisms are combined in a single material in order to target a more broad spectrum of toxic agents and to improve the performance of the materials. Recent attempts to combine materials with either adsorptive or catalytic properties into a composite material are promising, although the overall performance often suffers from competition for the agent between the adsorptive and catalytic domains in the composites. In this work, we propose that metal-organic frameworks (MOFs) could feature both adsorptive properties as well as catalytic properties in a single structural domain, thereby avoiding a reduction in the overall performance originating from competitive agent interactions. We showcase this concept using the MOF Ni3(BTP)2, which exhibits strong affinity and high capacity for the storage of a nerve agent simulant and a pesticide. Moreover, it is demonstrated that the adsorbed agents are efficiently degraded and that the nontoxic degradation products are rapidly expelled from the MOF pores. Its ability to catalyze the hydrolytic degradation of both organophosphate and organophosphorothioate compounds highlights another unique feature of this material. The presented concept illustrates the feasibility for developing materials that target a broader spectrum of agents via adsorption, catalysis, or both and by their broader reactivity toward different types of agents.

Capture and Decomposition of the Nerve Agent Simulant, DMCP, Using the Zeolitic Imidazolate Framework (ZIF-8)

Understanding mechanisms of decontamination of chemical warfare agents (CWA) is an area of intense research aimed at developing new filtration materials to protect soldiers and civilians in case of state-sponsored or terrorist attack. In this study, we employed complementary structural, chemical, and dynamic probes and in situ data collection, to elucidate the complex chemistry, capture, and decomposition of the CWA simulant, dimethyl chlorophosphonate (DMCP). Our work reveals key details of the reactive adsorption of DMCP and demonstrates the versatility of zeolitic imidazolate framework (ZIF-8) as a plausible material for CWA capture and decomposition. The in situ synchrotron-based powder X-ray diffraction (PXRD) and pair distribution function (PDF) studies, combined with Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), zinc K-edge X-ray absorption near edge structure (XANES), and Raman spectroscopies, showed that the unique structure, chemical state, and topology of ZIF-8 enable accessibility, adsorption, and hydrolysis of DMCP into the pores and revealed the importance of linker chemistry and Zn²⁺ sites for nerve agent decomposition. DMCP decontamination and decomposition product(s) formation were observed by thermogravimetric analysis, FT-IR spectroscopy, and phosphorus (P) K-edge XANES studies. Differential PDF analysis indicated that the average structure of ZIF-8 (at the 30 Å scale) remains unchanged after DMCP dosing and provided information on the dynamics of interactions of DMCP with the ZIF-8 framework. Using in situ PXRD and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), we showed that nearly 90% regeneration of the ZIF-8 structure and complete liberation of DMCP and decomposition products occur upon heating.