Utilizing Zirconium MOF-functionalized Fiber Substrates Prepared by Molecular Layer Deposition for Toxic Gas Capture and Chemical Warfare Agent Degradation.

Metal-organic frameworks (MOFs) are a class of porous organic-inorganic solids extensively explored for numerous applications owing to their catalytic activity and high surface area. In this work MOF thin films deposited in a one-step, molecular layer deposition (MLD), an all-gas-phase process, on glass wool fibers are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and their capabilities towards toxic industrial chemical (TIC) capture and chemical warfare agents (CWA) degradation are investigated. It is shown that despite low volume of the active material used, MOFs thin films are capable of removal of harmful gaseous chemicals from air stream and CWA from neutral aqueous environment. The results confirm that the MLD-deposited MOF thin films, amorphous and crystalline, are suitable materials for use in air filtration, decontamination, and physical protection against CWA and TIC.

Multifaceted Study of the Interactions between CPO-27-Ni and Polyurethane and Their Impact on Nitric Oxide Release Performance.

A multifaceted study involving focused ion beam scanning electron microscopy techniques, mechanical analysis, water adsorption measurements, and molecular simulations is employed to rationalize the nitric oxide release performance of polyurethane films containing 5, 10, 20, and 40 wt % of the metal-organic framework (MOF) CPO-27-Ni. The polymer and the MOF are first demonstrated to exhibit excellent compatibility. This is reflected in the even distribution and encapsulation of large wt % MOF loadings throughout the full thickness of the films and by the rather minimal influence of the MOF on the mechanical properties of the polymer at low wt %. The NO release efficiency of the MOF is attenuated by the polymer and found to depend on wt % of MOF loading. The formation of a fully connected network of MOF agglomerates within the films at higher wt % is proposed to contribute to a more complex guest transport in these formulations, resulting in a reduction of NO release efficiency and film ductility. An optimum MOF loading of 10 wt % is identified for maximizing NO release without adversely impacting the polymer properties. Bactericidal efficacy of released NO from the films is demonstrated against Pseudomonas aeruginosa, with a >8 log10 reduction in cell density observed after a contact period of 24 h.

Hierarchically Porous Silk/Activated-Carbon Composite Fibres for Adsorption and Repellence of Volatile Organic Compounds.

Fabrics comprised of porous fibres could provide effective passive protection against chemical and biological (CB) threats whilst maintaining high air permeability (breathability). Here, we fabricate hierarchically porous fibres consisting of regenerated silk fibroin (RSF) and activated-carbon (AC) prepared through two fibre spinning techniques in combination with ice-templating-namely cryogenic solution blow spinning (Cryo-SBS) and cryogenic wet-spinning (Cryo-WS). The Cryo-WS RSF fibres had exceptionally small macropores (as low as 0.1 µm) and high specific surface areas (SSAs) of up to 79 m2·g-1. The incorporation of AC could further increase the SSA to 210 m2·g-1 (25 wt.% loading) whilst also increasing adsorption capacity for volatile organic compounds (VOCs).

Metal-Organic Framework-Activated Carbon Composite Materials for the Removal of Ammonia from Contaminated Airstreams.

Metal-organic frameworks (MOFs) are a class of porous materials that show promise in the removal of toxic industrial chemicals (TICs) from contaminated airstreams, though their development for this application has so far been hindered by issues of water stability and the wide availability and low cost of traditionally used activated carbons. Here a series of three MOF-activated carbon composite materials with different MOF to carbon ratios are prepared by growing STAM-17-OEt crystals inside the commercially available BPL activated carbon. The composite materials display excellent water stability and increased uptake of ammonia gas when compared to unimpregnated carbon. Such properties make these composites very promising in the fields of air purification and personal protective equipment.

The impact of canister geometry on chemical biological radiological and nuclear filter performance: A computational fluid dynamics analysis.

Steady-state axisymmetric simulations using the Reynolds-Averaged Navier-Stokes equations have been carried out in order to optimize the performance of a Chemical, Biological, Radiological, and Nuclear (CBRN) canister filter for its use in a powered air-purifying respirator (PAPR). Alterations have been made to the shape of the canister, the spacing of the rear wall of the canister with regard to the carbon filter, and the bracketing between (i) the particulate filter and the carbon bed and (ii) the carbon bed and the canister wall. The pressure drops across the canister and the residence time distribution at the rear of the carbon bed have been analyzed in detail based on an extensive parametric analysis involving the aforementioned variations. It has been demonstrated that the non-uniform porosity profile of the carbon bed resulted in alternating regions of high and low velocity close to the canister wall, providing a possible route for breakthrough. Designs, which included a bracket at the rear of the carbon bed, blocked this route and consequently had a longer minimum mean residence time than those, which did not. It has also been shown that the spacing between the carbon bed and the canister rear wall had a large impact on both residence time and pressure drop. In cases where the carbon backed directly onto the canister rear wall flow in the axial direction from the outside wall toward the canister axis resulted in far greater pressure drop and a reduction in minimum mean residence time within the carbon bed.

Hydrolytic stability in hemilabile metal-organic frameworks.

Highly porous metal-organic frameworks (MOFs), which have undergone exciting developments over the past few decades, show promise for a wide range of applications. However, many studies indicate that they suffer from significant stability issues, especially with respect to their interactions with water, which severely limits their practical potential. Here we demonstrate how the presence of 'sacrificial' bonds in the coordination environment of its metal centres (referred to as hemilability) endows a dehydrated copper-based MOF with good hydrolytic stability. On exposure to water, in contrast to the indiscriminate breaking of coordination bonds that typically results in structure degradation, it is non-structural weak interactions between the MOF's copper paddlewheel clusters that are broken and the framework recovers its as-synthesized, hydrated structure. This MOF retained its structural integrity even after contact with water for one year, whereas HKUST-1, a compositionally similar material that lacks these sacrificial bonds, loses its crystallinity in less than a day under the same conditions.

Adsorption and Detection of Hazardous Trace Gases by Metal-Organic Frameworks.

The quest for advanced designer adsorbents for air filtration and monitoring hazardous trace gases has recently been more and more driven by the need to ensure clean air in indoor, outdoor, and industrial environments. How to increase safety with regard to personal protection in the event of hazardous gas exposure is a critical question for an ever-growing population spending most of their lifetime indoors, but is also crucial for the chemical industry in order to protect future generations of employees from potential hazards. Metal-organic frameworks (MOFs) are already quite advanced and promising in terms of capacity and specific affinity to overcome limitations of current adsorbent materials for trace and toxic gas adsorption. Due to their advantageous features (e.g., high specific surface area, catalytic activity, tailorable pore sizes, structural diversity, and range of chemical and physical properties), MOFs offer a high potential as adsorbents for air filtration and monitoring of hazardous trace gases. Three advanced topics are considered here, in applying MOFs for selective adsorption: (i) toxic gas adsorption toward filtration for respiratory protection as well as indoor and cabin air, (ii) enrichment of hazardous gases using MOFs, and (iii) MOFs as sensors for toxic trace gases and explosives.

Three-dimensional protonic conductivity in porous organic cage solids.

Proton conduction is a fundamental process in biology and in devices such as proton exchange membrane fuel cells. To maximize proton conduction, three-dimensional conduction pathways are preferred over one-dimensional pathways, which prevent conduction in two dimensions. Many crystalline porous solids to date show one-dimensional proton conduction. Here we report porous molecular cages with proton conductivities (up to 10(-3) S cm(-1) at high relative humidity) that compete with extended metal-organic frameworks. The structure of the organic cage imposes a conduction pathway that is necessarily three-dimensional. The cage molecules also promote proton transfer by confining the water molecules while being sufficiently flexible to allow hydrogen bond reorganization. The proton conduction is explained at the molecular level through a combination of proton conductivity measurements, crystallography, molecular simulations and quasi-elastic neutron scattering. These results provide a starting point for high-temperature, anhydrous proton conductors through inclusion of guests other than water in the cage pores.

Acid loaded porphyrin-based metal-organic framework for ammonia uptake.

A porphyrin-based metal-organic framework is shown to be structurally stable towards acid loading using either hydrochloric or formic acid. The capacity of this material as an ammonia sorbent was analysed using micro-breakthrough experiments in both dry and humid ammonia flows. The acid loaded material exhibited excellent uptake in comparison with the parent MOF.

Impact of water coadsorption for carbon dioxide capture in microporous polymer sorbents.

Alcohol-containing polymer networks synthesized by Friedel-Crafts alkylation have surface areas of up to 1015 m(2)/g. Both racemic and chiral microporous binaphthol (BINOL) networks can be produced by a simple, one-step route. The BINOL networks show higher CO(2) capture capacities than their naphthol counterparts under idealized, dry conditions. In the presence of water vapor, however, these BINOL networks adsorb less CO(2) than more hydrophobic analogues, suggesting that idealized measurements may give a poor indication of performance under more realistic carbon capture conditions.

Reversible water uptake by a stable imine-based porous organic cage.

A crystalline porous organic cage molecule, CC3, is shown to adsorb up to 20.1 wt% water reversibly. This was confirmed by both gravimetric sorption and by crystallographic analysis. Crystals of CC3 are stable in boiling water for at least 4 h. The surprising chemical and supramolecular stability of these imine-based molecular crystals suggests scope for practical applications in humid environments.

Enhanced stability of Cu-BTC MOF via perfluorohexane plasma-enhanced chemical vapor deposition.

Metal organic frameworks (MOFs) are a leading class of porous materials for a wide variety of applications, but many of them have been shown to be unstable toward water. Cu-BTC (1,3,5 benzenetricarboxylic acid, BTC) was treated with a plasma-enhanced chemical vapor deposition (PECVD) of perfluorohexane creating a hydrophobic form of Cu-BTC. It was found that the treated Cu-BTC could withstand high humidity and even submersion in water much better than unperturbed Cu-BTC. Through Monte Carlo simulations it was found that perfluorohexane sites itself in such a way within Cu-BTC as to prevent the formation of water clusters, hence preventing the decomposition of Cu-BTC by water. This PECVD of perfluorohexane could be exploited to widen the scope of practical applications of Cu-BTC and other MOFs.

Characterization of a novel G-protein coupled receptor from the parasitic nematode H. contortus with high affinity for serotonin.

The neurotransmitter serotonin (5HT) has been shown to modulate mobility, feeding, egg-laying, and defecation behaviors in the saprophytic nematode Caenorhabditis elegans. Although the effects of serotonin on these behaviors in parasitic nematodes is under study, little is known about the diversity, ontogeny, signaling, and pharmacology of serotonin receptors in these organisms. In an effort to increase our understanding of this system, we cloned and characterized a novel cDNA (5HT1Hc) from the parasitic nematode Haemonchus contortus that has high amino acid sequence homology with known G-protein coupled 5HT1-receptors from invertebrates and vertebrates. Transcript expression studies in four development stages (egg, L1/L2, L3, and adult) revealed the presence of the mRNA in the L1/L2, L3, and adult stages. Membranes from insect cells (Sf9) expressing the 5HT1Hc-receptor cDNA displayed nanomolar binding affinity to serotonin and a unique pharmacological profile distinct from known invertebrate and mammalian 5HT-receptors. Receptor signaling studies with mammalian AV12 cells expressing the 5HT1Hc-receptor and the promiscuous G-protein, Galpha15, demonstrated dose-dependent intracellular signals with serotonin acting as an agonist. Together, these studies describe a novel invertebrate 5HT-receptor with high affinity for the indolealkylamine, serotonin, and pharmacological properties that do not conform to any known members of this superfamily of metabotropic receptors.