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

Permeable Self-Association of Metal-Organic Framework 808/Ag-Based Fiber Membrane for Broad-Spectrum and Highly Efficient Degradation of Biological and Chemical War Agents

The threat posed by biological and chemical warfare agents (BCWA) to national security, the environment, and personal health underscores the need for innovative chemical protective clothing. To address the limitations of conventional activated carbon materials, which are prone to falling off and adsorption saturation, an efficient self-association approach was introduced. In this study, we proposed the immobilization of metal-organic framework (MOF) 808 and Ag nanoparticles onto a polypropylene (PP) fiber membrane using a rapid self-association method facilitated by chitosan (CS). The MOF 808/Ag-based (PP-CS/808-Ag) fiber membrane demonstrated exceptional degradation efficiency, achieving a remarkable rate of t1/2 within 2 h for the mustard simulant 2-chloroethyl ethyl sulfide (2-CEES) and a rate of t1/2 = 4.12 min for the G-series simulant dimethyl 4-nitrophenylphosphate (DMNP). A theoretical computational model was developed to determine the overall reaction mechanism, and it was verified that MOF 808 and Ag nanoparticles were mainly involved in the hydrolysis process against 2-CEES and DMNP. The PP-CS/808-Ag composite fiber film was prepared as the core layer, and the fracture strength, bending resistance, and moisture permeability were better than those specified by many countries for biochemical protective clothing, showing that it has a broad application prospect in developing a generation of broad-spectrum bioprotective clothing.

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.

Boosted ability of ZIF-8 for early-stage adsorption and degradation of chemical warfare agent simulants

Efficient adsorption of hazardous substances from the environment is crucial owing to the considerable risks they pose to both humans and ecosystems. Consequently, the development of porous materials with strong adsorption capabilities for hazardous substances, such as chemical warfare agents (CWAs), is pivotal for safeguarding human lives. Specifically, the early-stage adsorption proficiency of the adsorbents plays a vital role in determining their effectiveness as ideal adsorbents. Herein, we report the efficient adsorption of CWA simulants using thermally treated ZIF-8 (T-ZIF-8). The T-ZIF-8 samples were prepared by subjecting ZIF-8 to a simple thermal treatment, which resulted in a more positive surface charge with extra open metal sites. Although the pore volume of T-ZIF-8 decreased after thermal treatment, the positive surface charge of T-ZIF-8 proved advantageous for the adsorption of the CWA simulants. As a result, the adsorption capacity of T-ZIF-8 for the CWA simulants improved compared to that of pure ZIF-8. Notably, T-ZIF-8 exhibited a remarkably enhanced adsorption ability in the early stage of exposure to the CWA simulants, possibly due to the effective polar interactions between T-ZIF-8 and the simulants via the electron-rich components within the CWA simulants. Moreover, the enhanced adsorption capacity of T-ZIF-8 led to the fast degradation of simulant compared to pure ZIF-8. T-ZIF-8 also demonstrated excellent stability over three adsorption cycles. These findings highlight that T-ZIF-8 is an outstanding material for the early-stage adsorption and degradation of CWA simulants, offering high effectiveness and stability.

Defective MOF-74 with ancillary open metal sites for the enhanced adsorption of chemical warfare agent simulants

The development of effective porous adsorbents plays a vital role in eliminating hazardous substances from the environment. Toxic chemicals, including chemical warfare agents (CWAs), pose significant risks to both humans and ecosystems, highlighting the urgency to create efficient porous adsorbents. Therefore, substantial attention has been directed towards advancing adsorption techniques for the successful eradication of CWAs from the environment. Herein, we demonstrate a rational approach for enhancing the adsorption capability of a porous metal-organic framework (MOF) by employing ancillary open metal sites within the MOF structure. To generate defective MOF-74 (D-MOF-74) with ancillary open metal sites, some of the 2,5-dihydroxy-1,4-bezenedicarboxylic acid (DHBDC) linkers originally present in the MOF-74 structure were replaced with 1,4-benzenedicarboxylic acid (BDC) linkers. The absence of hydroxyl groups in the BDC linkers compared to the original DHBDC linkers creates ancillary open metal sites, which enhance the adsorption ability of D-MOF-74 for CWA simulants such as dimethyl methyl phosphonate, 2-chloroethyl ethyl sulfide, and methyl salicylate by providing effective interaction sites for the targeted molecules. However, excessive creation of open metal sites causes the collapse of the originally well-developed MOF-74 structure, resulting in a substantial reduction in its empty space and a subsequent decline in adsorption efficiency. Thus, to produce a defective MOF with the best performance, it is necessary to replace an appropriate amount of organic linker and create suitable open metal sites. Moreover, D-MOF-74 displays excellent recyclability during consecutive adsorption cycles without losing its original structure and morphology, suggesting that D-MOF-74 is an effective and stable material for the removal of CWA simulants.

Enhanced adsorption capacity of ZIF-8 for chemical warfare agent simulants caused by its morphology and surface charge

The effective separation of toxic chemicals, including chemical warfare agents (CWAs), from the environment via adsorption is of great importance because such chemicals pose a significant threat to humans and ecosystems. To this end, the development of effective porous adsorbents for CWA removal has received significant attention. Understanding the specific interactions between adsorbents and CWAs must precede for the development of effective adsorbents. Herein, we report the relationship between the adsorption capacity of porous ZIF-8 and its morphological and surface characteristics. Four types of ZIF-8, which have different morphologies (such as cubic, rhombic dodecahedron, and leaf- and plate-shaped samples), were selectively prepared. The four types of ZIF-8 were found to have different surface charges owing to dissimilarly exposed components on the surfaces and additionally incorporated components. The specific surface charges of ZIF-8 were found to be closely related to their adsorption capacities for CWA simulants such as 2-chloroethyl ethyl sulfide (CEES) and dimethyl methyl phosphonate (DMMP). Cubic ZIF-8, with the most positive surface charge among four ZIF-8 samples, exhibited the highest adsorption capacity for CEES and DMMP via the effective polar interaction. Moreover, ZIF-8 exhibited excellent recyclability without losing its adsorption capacity and without critical morphological or structural changes.

XRD and Spectroscopic Investigations of ZIF-Microchannel Glass Plates Composites

In this study, new composite materials comprising zeolitic imidazolate framework (ZIF) structures and microchannel glass (MCG) plates were fabricated using the hydrothermal method and their morphological and spectral properties were investigated using XRD, SEM, FTIR, and Raman spectroscopy. XRD studies of powder samples revealed the presence of an additional phase for a ZIF-8 sample, whereas ZIF-67 samples, which were prepared through two different chemical routes, showed no additional phases. A detailed analysis of the FTIR and micro-Raman spectra of the composite samples revealed the formation of stable ZIF structures inside the macropores of the MCG substrate. The hydrophilic nature of the MCG substrate and its interaction with the ZIF structure resulted in the formation of stable ZIF-MCG composites. We believe that these composite materials may find a wide range of important applications in the field of sensors, molecular sieving.

Tuning luminescence of the fluorescent molecule 2-(2-hydroxyphenyl)-1H-benzimidazole via zeolitic imidazolate framework-8

Zeolitic imidazolate framework-8 (ZIF-8) is one of the most promising metal-organic frameworks because of its excellent high porosity, stability and geometrically well-defined structure. However, the application of ZIF-8 in the field of fluorescent molecular sensing has not been intensively explored. Our work demonstrates the versatility of ZIF-8 as a carrier material, which can be used for small molecule [2-(2-hydroxyphenyl)-1H-benzimidazole (HPBI)] capture and fluorescence enhancement. ZIF-8 displays luminescent behavior changes when combined with HPBI, as the emission peaks of ZIF-8 and HPBI are located in the same range for resonance enhancement of fluorescence. The results of the experiment indicate that the fluorescence enhancement effect will change in the presence of different concentrations of HPBI. We propose that the pore structure of ZIF-8 could provide an opportunity for the adsorption of HPBI molecules, and eventually the adsorption would saturate. The high porosity of ZIF-8 provides the path to HPBI aggregation or entrance into the ZIF-8 internal structure. Our results suggest that ZIF-8 may offer great promise for molecular fluorescence sensing.

Directly decorated CeY zeolite for O2-selective adsorption in O2/N2 separation at ambient temperature

The traditional zeolites used in air separation are generally N₂-selective adsorbents. It was found for the first time that the O₂/N₂ adsorption selectivity can be reversed by directly decorating the Ce metal ion sites of a traditional Y zeolite with imidazole molecules, which results in a novel O₂ adsorbent. The O₂/N₂ selectivity changes from 0.9 to 1.6 under normal conditions, and most importantly, the O₂ adsorbent is recyclable. The in situ XPS characterization results indicate that the imidazole modification can change the electronic state of Ce in the Y zeolite and increase its affinity for O₂, which is confirmed by theoretical calculations. Dynamic breakthrough adsorption experiments show that the adsorbent has significant application potential in air separation.

A stable and plug-and-play aluminium/titanium dioxide/metal-organic framework/silver composite sheet for sensitive Raman detection and photocatalytic removal of 4-aminothiophenol

The sensitive detection and rapid removal of 4-aminothiophenol (4-ATP, a poisonous pesticide) demand special design to potential substrates. Herein, a metal-organic framework (ZIF-8) and Ag nanoparticles were fabricated one by one on the TiO₂ coated Al sheet, and thus the Al-TiO₂-ZIF-8-Ag sheet with sandwich structure was successfully synthesized. The cost-effective Al-TiO₂-ZIF-8-Ag sheet (3.7 wt% Ag) possessed a low detection concentration of 1 × 10^-9 M towards 4-ATP, and surface-enhanced Raman scattering (SERS) analytical enhanced factor (AEF) of the Al-TiO₂-ZIF-8-Ag was 2.6 × 10⁶, which was higher than other similar substrates. Furthermore, 4-ATP can be selectively and repeatedly detected on the Al-TiO₂-ZIF-8-Ag even through it was in real samples. It indicated that the Al-TiO₂-ZIF-8-Ag was a very active and stable SERS materials for the monitoring of 4-ATP. Importantly, the substrate exhibited faster and more efficient photocatalytic activity for 4-ATP degradation. The SERS and photocatalytic mechanisms of 4-ATP on the Al-TiO₂-ZIF-8-Ag substrate were proposed. The cost-effective Al-TiO₂-ZIF-8-Ag sheet with double function is plug-and-play, and could be used in the detection and treatment of pollutants in wastewater.