Highly tunable metal–organic framework (MOF) materials, including, for example, UiO-66-NH2, are known to be effective catalysts to degrade chemical warfare agents (CWAs) with half-lives near 1 min. ...Therefore, many researchers have been actively working on producing supported MOF materials to improve application effectiveness by using relatively slow solvothermal synthesis or repetitious stepwise layer-by-layer methods. Herein, we demonstrate a facile route to rapidly assemble presynthesized UiO-66-NH2 crystals onto nonwoven polypropylene (PP) fibrous mats at ambient temperature. Crystal assembly is chemically directed using β-cyclodextrin (β-CD) and cetyltrimethylammonium bromide (CTAB) as surfactant assembly agents, where the agents quickly (within 5 min) self-assemble on the crystal surface and promote physically robust chemical surface attachment while simultaneously impeding solution-phase crystal agglomeration. Furthermore, we find that when the PP is preconditioned using conformal metal oxide thin films, including Al2O3, TiO2, or ZnO formed via atomic layer deposition (ALD), the hydrophilic metal oxide surface further helps improve assembly uniformity and MOF mass loading, producing MOF crystal loading as high as 40 wt % and an overall BET surface area exceeding 200 m2/g(MOF+Fiber). Using these surface-assembled MOFs, we observe catalytic degradation of dimethyl 4-nitrophenyl phosphate (DMNP), a CWA simulant, with a half-life of less than 5 min.
Metal–organic frameworks (MOFs) chemically bound to polymeric microfibrous textiles show promising performance for many future applications. In particular, Zr-based UiO-66-family MOF-textiles have ...been shown to catalytically degrade highly toxic chemical warfare agents (CWAs), where favorable MOF/polymer bonding and adhesion are attained by placing a nanoscale metal-oxide layer on the polymer fiber preceding MOF growth. To date, however, the nucleation mechanism of Zr-based MOFs on different metal oxides and how product performance is affected are not well understood. Herein, we provide new insight into how different inorganic nucleation films (i.e., Al2O3, ZnO, or TiO2) conformally coated on polypropylene (PP) nonwoven textiles via atomic layer deposition (ALD) influence the quality, overall surface area, and the fractional yield of UiO-66-NH2 MOF crystals solvothermally grown on fiber substrates. Of the materials explored, we find that TiO2 ALD layers lead to the most effective overall MOF/fiber adhesion, uniformity, and a rapid catalytic degradation rate for a CWA simulant, dimethyl p-nitrophenyl phosphate (DMNP) with t 1/2 = 15 min, 580-fold faster than the catalytic performance of untreated PP textiles. Interestingly, compared to ALD TiO2 and Al2O3, ALD ZnO induces a larger MOF yield in solution and mass loading on PP fibrous mats. However, this larger MOF yield is ascribed to chemical instability of the ZnO layer under MOF formation condition, leading to Zn2+ ions that promote further homogeneous MOF growth. Insights presented here improve understanding of compatibility between active MOF materials and substrate surfaces, which we believe will help advanced MOF composite materials for a variety of useful functions.
Abatement of chemical hazards using adsorptive metal‐organic frameworks (MOFs) attracts substantial attention, but material stability and crystal integration into functional systems remain key ...challenges. Herein, water‐stable, polymer fiber surface–oriented M–TCPP M = Cu, Zn, and Co; H2TCPP = 5,10,15,20‐tetrakis(4‐carboxyphenyl)porphyrin 2D MOF crystals are fabricated using a facile hydroxy double salt (HDS) solid‐source conversion strategy. For the first time, Cu–TCPP is formed from a solid source and confirmed to be highly adsorptive for NH3 and 2‐chloroethyl ethyl sulfide (CEES), a blistering agent simulant, in humid (80% relative humidity (RH)) conditions. Moreover, the solid HDS source is found as a unique new approach to control MOF thin‐film crystal orientation, thereby facilitating radially arranged MOF crystals on fibers. On a per unit mass of MOF basis in humid conditions, the MOF/fiber composite enhances NH3 adsorptive capacity by a factor of 3 compared to conventionally prepared MOF powders. The synthesis route extends to other MOF/fiber composite systems, therefore providing a new route for chemically protective materials.
Chemical protective metal‐organic framework (MOF)/fiber composites highly adsorptive for NH3 and 2‐chloroethyl ethyl sulfide (CEES), a vesicant sulfur mustard simulant, are fabricated. The facile synthetic route employed here for the composite systems shows not only synthetic generality, but also extends to other MOF/fiber composite systems that cannot be readily facilitated by conventional synthetic approaches.
The threat associated with chemical warfare agents (CWAs) motivates the development of new materials to provide enhanced protection with a reduced burden. Metal–organic frame‐works (MOFs) have ...recently been shown as highly effective catalysts for detoxifying CWAs, but challenges still remain for integrating MOFs into functional filter media and/or protective garments. Herein, we report a series of MOF–nanofiber kebab structures for fast degradation of CWAs. We found TiO2 coatings deposited via atomic layer deposition (ALD) onto polyamide‐6 nanofibers enable the formation of conformal Zr‐based MOF thin films including UiO‐66, UiO‐66‐NH2, and UiO‐67. Cross‐sectional TEM images show that these MOF crystals nucleate and grow directly on and around the nanofibers, with strong attachment to the substrates. These MOF‐functionalized nanofibers exhibit excellent reactivity for detoxifying CWAs. The half‐lives of a CWA simulant compound and nerve agent soman (GD) are as short as 7.3 min and 2.3 min, respectively. These results therefore provide the earliest report of MOF–nanofiber textile composites capable of ultra‐fast degradation of CWAs.
Skewering nerve agents: Conformal metal–organic framework (MOF) kebab structures decorated on nanofibers that can degrade chemical warfare agents within minutes are described. These MOF–nanofiber composites show excellent reactivity towards both simulant and nerve agent soman (GD).
Organophosphonate-based nerve agents, such as VX, Sarin (GB), and Soman (GD), are among the most toxic chemicals to humankind. Recently, we have shown that Zr-based metal–organic frameworks (Zr-MOFs) ...can effectively catalyze the hydrolysis of these toxic chemicals for diminishing their toxicity. On the other hand, utilizing these materials in powder form is not practical, and developing scalable and economical processes for integrating these materials onto fibers is crucial for protective gear. Herein, we report a scalable, template-free, and aqueous solution-based synthesis strategy for the production of Zr-MOF-coated textiles. Among all MOF/fiber composites reported to date, the MOF-808/polyester fibers exhibit the highest rates of nerve agent hydrolysis. Moreover, such highly porous fiber composites display significantly higher protection time compared to that of its parent fabric for a mustard gas simulant, 2-chloroethyl ethyl sulfide (CEES). A decreased diffusion rate of toxic chemicals through the MOF layer can provide time needed for the destruction of the harmful species.
Rapid room-temperature synthesis of metal–organic frameworks (MOFs) is highly desired for industrial implementation and commercialization. Here we find that a (Zn,Cu) hydroxy double salt (HDS) ...intermediate formed in situ from ZnO particles or thin films enables rapid growth (<1 min) of HKUST-1 (Cu3(BTC)2) at room temperature. The space-time-yield reaches >3 × 104 kg·m–3·d–1, at least 1 order of magnitude greater than any prior report. The high anion exchange rate of (Zn,Cu) hydroxy nitrate HDS drives the ultrafast MOF formation. Similarly, we obtained Cu-BDC, ZIF-8, and IRMOF-3 structures from HDSs, demonstrating synthetic generality. Using ZnO thin films deposited via atomic layer deposition, MOF patterns are obtained on pre-patterned surfaces, and dense HKUST-1 coatings are grown onto various form factors, including polymer spheres, silicon wafers, and fibers. Breakthrough tests show that the MOF-functionalized fibers have high adsorption capacity for toxic gases. This rapid synthesis route is also promising for new MOF-based composite materials and applications.
UiO-66 is a Zr-based MOF that is being highly investigated for a wide variety of small molecule gas separations since it possess unprecedented thermal, chemical, and mechanical stability. In this ...work, we have investigated the performance of various functionalized variations of UiO-66 (UiO-66-OH, UiO-66-(OH)2, UiO-66-NO2, UiO-66-NH2, UiO-66-SO3H, and UiO-66-(COOH)2) towards ammonia removal from air. Functionalized UiO-66 analogs have been synthesized solvothermally and characterized using ammonia breakthrough measurements under dry and humid (80% RH) air conditions along with powder X-ray diffraction (PXRD) patterns and results from BET modeling of N2 adsorption isotherms. Counter to chemical intuition, our study demonstrates that the ammonia capacities of UiO-66-SO3H and UiO-66-(COOH)2 are lower than UiO-66-OH and UiO-66-NH2. This is due to significant reduction in the framework porosity (surface area and pore volume) upon functionalization with bulky functional groups such as –COOH and –SO3H. The –OH group is the least bulky functional group considered in the work and interacts favorably with ammonia. UiO-66-OH has a capacity of ~5.7mmol/g for ammonia under dry conditions which is very close to the ammonia removal goal of 0.1g/g MOF (or ~6mmol/g). However, we observed a decrease in the ammonia capacities of functionalized UiO-66 variations under humid conditions due to competition between water and ammonia molecules for adsorption on the active sites. Overall, balancing the water adsorption behavior and high selectivity and high capacity for ammonia is crucial to developing new adsorbents for ammonia removal from air.
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•UiO-66 and 6 variants were synthesized and studied for adsorption of ammonia from air.•Functional groups were chosen for high interaction with ammonia.•Hydroxyl groups interact the most effectively with ammonia at low concentration.•Breakthrough curves were measured on all materials using a microbreakthrough system.•Large-pore MOFs (>10Å) are necessary for efficient use of complex functionalization.
Chemical warfare agents containing phosphonate ester bonds are among the most toxic chemicals known to mankind. Recent global military events, such as the conflict and disarmament in Syria, have ...brought into focus the need to find effective strategies for the rapid destruction of these banned chemicals. Solutions are needed for immediate personal protection (for example, the filtration and catalytic destruction of airborne versions of agents), bulk destruction of chemical weapon stockpiles, protection (via coating) of clothing, equipment and buildings, and containment of agent spills. Solid heterogeneous materials such as modified activated carbon or metal oxides exhibit many desirable characteristics for the destruction of chemical warfare agents. However, low sorptive capacities, low effective active site loadings, deactivation of the active site, slow degradation kinetics, and/or a lack of tailorability offer significant room for improvement in these materials. Here, we report a carefully chosen metal-organic framework (MOF) material featuring high porosity and exceptional chemical stability that is extraordinarily effective for the degradation of nerve agents and their simulants. Experimental and computational evidence points to Lewis-acidic Zr(IV) ions as the active sites and to their superb accessibility as a defining element of their efficacy.
Metal organic framework (MOF-74) analogs have been synthesized using cobalt, magnesium, nickel, and zinc metal centers. The capability of these materials to remove ammonia, cyanogen chloride, and ...sulfur dioxide from air has been evaluated via fixed-bed breakthrough testing in both dry and humid conditions. Octane breakthrough tests were performed to determine the physisorption capacities of the materials. All materials were stored in air prior to use. Dynamic breakthrough capacities of the analogs were compared to 13X zeolite and BPL activated carbon. The impact of the metal center on the adsorption behavior is illustrated with each analog providing different ammonia and cyanogen chloride adsorption capacities. The results provide an important step in the assessment of the potential of MOFs to function as porous adsorbent materials.
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