Search

This paper describes a novel synthetic approach for the conversion of zero-valent copper metal into a conductive two-dimensional layered metal-organic framework (MOF) based on 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) to form Cu

Current approaches to create zirconium-based metal-organic framework (MOF) fabric composites for catalysis, water purification, wound healing, gas sorption, and other applications often rely on toxic solvents, long reaction/post processing times, and batch methods hindering process scalability. Here, a novel mechanism was reported for rapid UiO-66-NH

Summary Zirconium-based metal-organic frameworks (Zr-MOFs) with Lewis-acidic sites are potent catalysts for degrading organophosphorus nerve agents. However, a volatile basic solution must regenerate the Zr-MOF catalysts, challenging its real-world implementation. By crosslinking polyethylene imine with an epoxide in the presence of selected Zr-MOFs, we prepared Zr-MOF/hydrogel composite catalysts for the rapid degradation of organophosphorus chemicals under atmospheric conditions. We developed a series of Zr-MOF hydrogel powder composites varying in Zr-node connectivity, linker functionality, and topology. The MOF-808 hydrogel powder was the highest-performing MOF-based composite for the hydrolysis of organophosphorus nerve-agent simulants. We coated the MOF-808 hydrogel onto a textile, and the composite rapidly detoxified nerve-agent simulants and actual nerve agents. The resulting half-lives are the fastest reaction rates to date among MOF-based composite materials, representing a critical step toward the production of protective gear for the instantaneous detoxification of nerve agents in practical conditions.

Protocols to create metal-organic framework (MOF)/polymer composites for separation, chemical capture, and catalytic applications currently rely on relatively slow solution-based processing to form single MOF composites. Here, we report a rapid, high-yield sorption-vapor method for direct simultaneous growth of single and multiple MOF materials onto untreated flexible and stretchable polymer fibers and films. The synthesis utilizes favorable reactant absorption into polymers coupled with rapid vapor-driven MOF crystallization to form high surface area (>250 m2/gcomposite) composites, including UiO-66-NH2, HKUST-1, and MOF-525 on spandex, nylon, and other fabrics. The resulting composites are robust and maintain their functionality even after stretching. Stretchable MOF fabrics enable rapid solid-state hydrolysis of the highly toxic chemical warfare agent soman and paraoxon-methyl simulant. We show that this approach can readily be scaled by solution spray-coating of MOF precursors and to large area substrates.

Thermodynamic and kinetic properties of molecular adsorption and transport in metal-organic frameworks (MOFs) are crucially important for many applications, including gas adsorption, filtration, and remediation of harmful chemicals. Using the in situ 1H nuclear magnetic resonance (NMR) isotherm technique, we measured macroscopic thermodynamic and kinetic properties such as isotherms and rates of mass transfer while simultaneously obtaining microscopic information revealed by adsorbed molecules via NMR. Upon investigating isopropyl alcohol adsorption in MOF UiO-66 by in situ NMR, we obtained separate isotherms for molecules adsorbed at distinct environments exhibiting distinct NMR characteristics. A mechanistic view of the adsorption process is obtained by correlating such resolved isotherms with the cage structure effect on the nucleus-independent chemical shift, molecular dynamics such as the crowding effect at high loading levels, and the loading level dependence of the mass transfer rate as measured by NMR and elucidated by classical Monte Carlo simulations.

We report an all solid dry complex oxidizing agent against sulfur mustard (HD) and its simulant 2-Chloroethyl ethyl sulfide (2-CEES). Polymer complexes of poly(N-vinylpyrrolidone) (PVP) with hydrog...

Chemical warfare agents (CWAs), such as sarin and sulfur mustard, continue to be a threat due to their high toxicity coupled with worldwide usage. Metal–organic frameworks (MOFs) are efficient mate...

The most recent global health crisis caused by the SARS-CoV-2 outbreak and the alarming use of chemical warfare agents highlight the necessity to produce efficient protective clothing and masks against biohazard and chemical threats. However, the development of a multifunctional protective textile is still behind to supply adequate protection for the public. To tackle this challenge, we designed multifunctional and regenerable N-chlorine based biocidal and detoxifying textiles using a robust zirconium metal-organic framework (MOF), UiO-66-NH2, as a chlorine carrier which can be easily coated on textile fibers. A chlorine bleaching converted the amine groups located on the MOF linker to active N-chlorine structures. The fibrous composite exhibited rapid biocidal activity against both Gram-negative bacteria (E. coli) and Gram-positive bacteria (S. aureus) with up to a 7 log reduction within 5 min for each strain as well as a 5 log reduction of SARS-CoV-2 within 15 min. Moreover, the active chlorine loaded MOF/fiber composite selectively and rapidly degraded sulfur mustard and its chemical simulant 2-chloroethyl ethyl sulfide (CEES) with half-lives less than 3 minutes. The versatile MOF-based fibrous composite designed here has the potential to serve as protective cloth against both biological and chemical threats.

Adsorbent filters often use activated carbons to remove a wide range of toxic chemicals from air. It is of interest to know if filter performance for these compounds can be diffusion limited as a r...

Gas capture and sequestration are valuable properties of metal-organic frameworks (MOFs) driving tremendous interest in their use as filtration materials for chemical warfare agents. Recently, the Zr-based MOF UiO-67 was shown to effectively adsorb and decompose the nerve-agent simulant, dimethyl methylphosphonate (DMMP). Understanding mechanisms of MOF-agent interaction is challenging due to the need to distinguish between the roles of the MOF framework and its particular sites for the activation and sequestration process. Here, we demonstrate the quantitative tracking of both framework and binding component structures using in situ X-ray total scattering measurements of UiO-67 under DMMP exposure, pair distribution function analysis, and theoretical calculations. The sorption and desorption of DMMP within the pores, association with linker-deficient Zr6 cores, and decomposition to irreversibly bound methyl methylphosphonate were directly observed and analyzed with atomic resolution. Metal-organic frameworks have been shown to adsorb and decompose chemical warfare agents, but their mechanism of action is not completely understood. Here the authors quantitatively track the binding and decomposition product structures of nerve-agent simulant dimethyl methylphosphonate in host UiO-67 through in situ X-ray total scattering measurements, pair distribution function analysis, and density functional theory calculations. BASF; U.S. Army Research Office [W911NF15-2-0107]; Defense Threat Reduction AgencyUnited States Department of DefenseDefense Threat Reduction Agency [CB3587]; DOE Office of ScienceUnited States Department of Energy (DOE) [DE-SC0012704] Published version M.W.T. gratefully acknowledges support from BASF. A.M.P., D.T., and A.I.F. acknowledge support by the U.S. Army Research Office under grant number W911NF15-2-0107. J.J.M. and W.O.G. thank the Defense Threat Reduction Agency for support under program CB3587. This research used beamline 28-ID-2 of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704. Advanced Research Computing at Virginia Tech is gratefully acknowledged for computational resources.

Metal-organic frameworks (MOFs) are promising candidates for the catalytic hydrolysis of nerve agents and their simulants. Though highly efficient, bulk water and volatile bases are often required for hydrolysis with these MOF catalysts, preventing real-world implementation. Herein we report a generalizable and scalable approach for integrating MOFs and non-volatile polymeric bases onto textile fibers for nerve agent hydrolysis. Notably, the composite material showed similar reactivity under ambient conditions compared to the powder material in aqueous alkaline solution. This represents a critical step toward a unified strategy for nerve agent hydrolysis in practical settings, which can significantly reduce the dimensions of filters and increase the efficiency of protective suits.

A strategy is developed to enhance the barrier protection of polyethylene oxide (PEO)-metal-organic framework (MOF) composite films against chemical warfare agent simulants. To achieve enhanced protection, an impermeable high-aspect-ratio filler in the form of Laponite RD (LRD) clay platelets was incorporated into a composite PEO film containing MOF UiO-66-NH2. The inclusion of the platelets aids in mitigating permeation of inert hydrocarbons (octane) and toxic chemicals (2-chloroethyl ethyl sulfide, 2-CEES) of dimensions/chemistry similar to prominent vesicant threats while still maintaining high water vapor transport rates (WVTR). By utilizing small-angle neutron scattering, small-angle X-ray scattering, and wide-angle X-ray scattering, the LRD platelet alignment of the films was determined, and the structure of the films was correlated with performance as a barrier material. Performance of the membranes against toxic chemical threats was assessed using permeation testing of octane and 2-CEES, a common simulant for the vesicant mustard gas, and breathability of the membranes was assessed using WVTR measurements. To assess their robustness, chemical exposure (in situ diffuse reflectance infrared Fourier transform spectroscopy) and mechanical (tensile strength) measurements were also performed. It was demonstrated that the barrier performance of the film upon inclusion of the LRD platelets exceeds that of other MOF-polymer composites found in the literature and that this approach establishes a new path for improving permselective materials for chemical protection applications.

A fullerene-based photosensitizer is incorporated postsynthetically into a Zr6 -based MOF, NU-1000, for enhanced singlet oxygen production. The structural organic linkers in the MOF platform also act as photosensitizers which contribute to the overall generation of singlet oxygen from the material under UV irradiation. The singlet oxygen generated by the MOF/fullerene material is shown to oxidize sulfur mustard selectively to the less toxic bis(2-chloroethyl)sulfoxide with a half-life of only 11 min.

Zirconium-based metal organic frameworks (Zr-MOFs) are highly chemically and thermally stable and have been of particular interest as reactive sorbents for chemical warfare agent (CWA) removal due to their fast and selective reactivity toward CWAs reported in buffer solutions. However, we find that decontamination of neat CWAs directly on Zr-MOFs, UiO-66, UiO-66-NH

Here we discuss the removal of nitrogen dioxide, an important toxic industrial chemical and pollutant, from air using the MOF UiO-66-NH2 . The amine group is found to substantially aid in the removal, resulting in unprecedented removal capacities upwards of 1.4 g of NO2 /g of MOF. Furthermore, whereas NO2 typically generates substantial quantities of NO on sorbents, the amount generated by UiO-66-NH2 is significantly reduced. Of particular significance is the formation of a diazonium ion on the aromatic ring of the MOF, and the potential reduction of NO2 to molecular nitrogen.

A pyrene-based metal-organic framework (MOF) NU-1000 was used as a heterogeneous photocatalyst for the degradation of a sulfur mustard simulant, 2-chloroethyl ethyl sulfide (CEES). Using irradiation from a commercially available and inexpensive ultraviolet (UV) light-emitting diode (LED), singlet oxygen (1O2) is generated by NU-1000 and selectively oxidizes CEES to the nontoxic product 2-chloroethyl ethyl sulfoxide (CEESO). More importantly, this method was tested on the warfare agent sulfur mustard (HD) for the first time using 1O2 and a MOF catalyst, and this method proved to be effective in oxidizing sulfur mustard to nontoxic products without forming the toxic sulfone by-product.

The structure of a molecule and its concentration can strongly influence diffusional properties for transport in nanoporous materials. We study mass transfer of alkanes in BPL activated carbon using the concentration-swing frequency response method, which can easily discriminate among mass transfer mechanisms. We measure concentration-dependent diffusion rates for n-hexane, n-octane, n-decane, 2,7-dimethyloctane, and cyclodecane, which have different carbon numbers and geometries: straight chain, branched chain, and cyclic. Micropore diffusion is determined to be the controlling mass transfer resistance except at low relative saturation for n-decane, where an external mass transfer resistance also becomes important, showing that the controlling mass transfer mechanism can change with system concentration. Micropore diffusion coefficients are found to be strongly concentration dependent. Adsorption isotherm slopes obtained from measured isotherms, the concentration-swing frequency response method, and a predictive method show reasonably good agreement.

Zirconium hydroxide was evaluated for the ability to detoxify chemical warfare agents GD, HD, and VX. Observed half-lives were 8.7 min, 2.3 h, and 1 min, respectively. Owing to its extremely fast reaction rate, the mechanism for VX was further characterized. Zirconium hydroxide samples were calcined at temperatures ranging from 150 to 900 °C to investigate the effect of surface speciation on VX hydrolysis rates. NMR, TGA/DSC, TEM, and potentiometric tritration reveal the importance of the acidic, bridging OH groups of Zr(OH)4 which are proposed to protonate and catalytically hydrolyze VX in a manner similar to autocatalysis by EMPA in solution.

Titania materials such as anatase (TiO2), nanotubular titania (NTT), and nanocrystalline titania (nTiO2) exhibit extremely short half-lives for VX, provided adequate surface-adsorbed water is present. The effect of coadsorbed water on the hydrolytic activity of these materials toward VX, GD, and HD was assessed to select the most promising candidate for study in self-decontaminating paints and coatings. The best candidate is nTiO2, primarily chosen for its extremely short VX half-life at quite high water-content. For the most part, imbedding nTiO2 into various coatings negatively impacts its reactivity. A notable exception is observed for the case of HD and nTiO2/Wax (a paint simulant), where a somewhat shorter half-life is observed compared to the nascent nTiO2 powder. However, encrusting a painted surface with nTiO2 powder, leaving it partly exposed rather than wholly imbedded, results in improved reactivity.

The metal-organic framework (MOF) HKUST-1 incorporated into a mixed-matrix membrane (MMM) exhibits enhanced water stability while maintaining gas removal capabilities commensurate with those of the free powder form., Metal–organic frameworks (MOFs) in their free powder form have exhibited superior capacities for many gases when compared to other materials, due to their tailorable functionality and high surface areas. Specifically, the MOF HKUST-1 binds small Lewis bases, such as ammonia, with its coordinatively unsaturated copper sites. We describe here the use of HKUST-1 in mixed-matrix membranes (MMMs) prepared from polyvinylidene difluoride (PVDF) for the removal of ammonia gas. These MMMs exhibit ammonia capacities similar to their hypothetical capacities based on the weight percent of HKUST-1 in each MMM. HKUST-1 in its powder form is unstable toward humid conditions; however, upon exposure to humid environments for prolonged periods of time, the HKUST-1 MMMs exhibit outstanding structural stability, and maintain their ammonia capacity. Overall, this study has achieved all of the critical and combined elements for real-world applications of MOFs: high MOF loadings, fully accessible MOF surfaces, enhanced MOF stabilization, recyclability, mechanical stability, and processability. This study is a critical step in advancing MOFs to a stable, usable, and enabling technology.

A previously described porous organic polymer (NU-POP-1) was evaluated against four representative chemical threats: ammonia, cyanogen chloride, sulfur dioxide, and octane. Ammonia, cyanogen chloride, and sulfur dioxide are examples of toxic industrial chemicals (TICs) spanning the range from highly basic to strong-acid forming substances, while octane is used to assess physical adsorption capacity. Experiments were carried out using a microbreakthrough test apparatus, which measures the adsorption capacity at saturation and gives an indication of the strength of adsorption. The NU-POP-1 material exhibited substantial removal capabilities against the majority of the toxic chemicals, with capacities as high as or better than an activated, impregnated carbon. The ability to remove the highly volatile toxic chemicals ammonia and cyanogen chloride was intriguing, as these chemicals typically require reactive moieities for removal. The present work presents a benchmark for toxic chemical removal, and future work will focus on incorporating functional groups targeting the toxic chemicals of interest.

The hydrolysis and fate of cyanogen chloride (CK) in the presence of triethylenediamine (TEDA)—a widely used carbon impregnant—in aqueous and nonaqueous (acetonitrile) media has been determined. In the presence of water, anticipated TEDA substitution is not observed; rather, simple base-catalyzed (OH−) hydrolysis to cyanic acid (HOCN; unstable in water, decomposing to CO2 and NH3) is the major reaction, accompanied by a series of complex side reactions (not involving TEDA) to form several persistent compounds. Thus, the role of TEDA, in the presence of water, is primarily a source of OH−. CK substitution at TEDA is observed in acetonitrile, again forming several complex, but quite different, species. Studies examining the removal of CK from humidified air streams by carbon impregnated with TEDA and/or basic Cu2+ (another common carbon impregnant) are consistent with simple hydrolysis being the major CK-removal mechanism; no TEDA substitution is observed in the presence of humidity/water. Considering the r...

Two carbons with different sulfur contents were prepared and oxidized either by heating in air or by chemical treatment. The samples were then tested as adsorbents of arsine in dynamic conditions at room temperature, both in dry conditions and in the presence of moisture. Chemical and structural features of the initial and arsine-exposed materials were analyzed by energy dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analyses, sorption of nitrogen and sorption of water. It was found that oxygen- and sulfur-containing groups participate in arsine oxidation to arsenic tri- and pentoxide and/or in the formation of arsenic sulfides. This occurred either via activation of oxygen or a direct involvement of these groups in reactions with arsine. A very hydrophilic surface of sulfur-containing carbons, which causes the presence of adsorbed water, even in dry conditions, enhances arsine removal. On the other hand, in moist conditions water totally occupies the pore system blocking the catalytic action of the surface toward oxidation, which leads to a very limited or zero AsH3 adsorption capacity.

Two carbons obtained from polymers containing no ash and commercial wood based carbons, as received and modified with nitrogen, were tested as adsorbents of arsine in dynamic conditions at room temperature. The chemical and structural features of the initial and exhausted carbons were analyzed by energy dispersive X-ray spectroscopy, X-ray fluorescence spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analyses, adsorption of nitrogen, and sorption of water. It was found that heteroatoms present on the surface of the carbons studied, namely oxygen, nitrogen, and sulfur, catalyze arsine oxidation mainly to arsenic tri- and pentoxide and/or in the formation of arsenic sulfides. When the surface has a high degree of hydrophilicity and water is present in the system it blocks these active centers resulting in the negligible arsine removal capacity. On the other hand, on a relatively hydrophobic surface with active nitrogen species arsine is adsorbed and oxidized to ars...

Vapor adsorption on porous materials for non-wetting adsorbent–adsorbate pairs, characterized by a Type 5 isotherm, results in low loading at low relative pressure and increased loading due to capillary condensation behavior at higher relative pressure. The relationship between capillary condensation and the Kelvin equation suggests that a simple expression can be developed in which the adsorption equilibrium is obtained from an integrated pore size distribution function. This new expression is shown to describe the Type 5 isotherms of water adsorption on activated carbon. In addition, this expression has useful properties including: (1) finite saturation limit, (2) readily calculated Henry’s constant, and (3) readily calculated heat of adsorption, (4) can be written explicitly in terms of partial pressure or adsorbed phase loading and (5) parameter values attributable to the distribution function.

Experimental data are reported for the desorption of bis-2-chloroethyl sulfide, (a sulfur mustard or HD) and its decomposition products from activated coconut shell carbon (CSC). The results show that under equilibrium conditions changes in the HD partial pressure are affected primarily by its loading and temperature of the adsorbent. The partial pressure of adsorbed HD is found to increase by about a decade for each 25 C increase in temperature for CSC containing 0.01--0.1 g/g HD. Adsorption equilibria of HD appear to be little affected by coadsorbed water. Although complicated by its decomposition, the distribution of adsorbed HD (of known amount) appears to occupy pores of similar energy whether dry or in the presence of adsorbed water. On dry CSC adsorbed HD appears stable, while in the presence of water its decomposition is marked by hydrolysis at low temperature and thermal decomposition at elevated temperatures. The principal volatile products desorbed are 1,4-thioxane, 2-chloroethyl vinyl sulfide and 1,4-dithiane, with the latter favoring elevated temperatures.

Carbon samples from the Munition Demilitarization Building (MDB) Banks 1 and 2 ventilation filters from the Anniston Chemical Agent Disposal Facility were analyzed for the level of GB and VX contamination following the completion of the GB agent and VX rocket campaigns. The results of this investigation, using either thermal desorption, headspace, or NMR analysis, showed no GB or VX above the minimum detectable level on either of these filter samples. The use of NMR analysis resulted in the discovery of a significant amount of hydrolysis products from these agents on the MDB Filter Bank 1 carbon, but none on the MDB Filter Bank 2 carbon. Evaluation of adsorbent capacity studies found that the MDB Filter Bank 2 carbon had the same filtering capacity as a new filter, whereas the MDB Filter Bank 1 carbon showed signs of chemical loading and 12% of its original adsorption capacity remained active.

Nonisothermal effects are known to be generally important in gas-phase adsorption processes. This paper considers the role of a weakly adsorbed carrier gas in pressure swing adsorption for purifica...

Adsorption equilibrium data have been measured for four refrigerant vapors (R-113, R-11, R-318, and R-22) on BPL activated carbon at three temperatures over a wide range of partial pressures using an automated isotherm apparatus. Special emphasis is placed on the design and operation of the apparatus to ensure the quality of these data. Isotherm data for each refrigerant vapor are analyzed for correct Henry's law behavior and correlated using three- and four-parameter functions with specified temperature dependencies. The functions employed in this study include (1) the Langmuir equation, (2) the Dubinin-Astakhov equation, (3) the virial equation, and (4) the modified Antoine equation. The Dubinin-Astakhov equation provides the best (or very comparable) fits, based on the variance, for R-113, R-11, and R-318. However, the Dubinin-Astakhov equation does not correctly describe the behavior of the R-22 data, resulting from its incorrect approach to Henry's law. Overall result show that, for adsorption of these refrigerants on BPL activated carbon, those correlations with exponents on the adsorbed-phase concentration terms greater than 1 generate the smallest variances.

The vapor filtration of AsCli by the adsorbent ASZMT is examined in this report. Microscalc testing is performed, with analysis of the concentration by FTIR. The effect of humidity on AsCh stability and filtration performance is considered. Large adsorption capacity is determined, approximately 4 mol/kg, by calculating a mass balance from the measured breakthrough results. Hydrochloric acid breaks through prior to AsCh under humid conditions.

Adsorption equilibria and NMR experiments were performed to study the adsorption and interactions of ammonia with metal-organic framework (MOF) HKUST-1, or Cu(3)(BTC)(2) (BTC = 1,3,5-benzenetricarboxylate). Ammonia capacities determined from chemical breakthrough measurements show significantly higher uptake capacities than from adsorption alone, suggesting a stronger interaction involving a potential reaction with the Cu(3)(BTC)(2) framework. Indeed, (1)H MAS NMR reveals that a major disruption of the relatively simple spectrum of Cu(3)(BTC)(2) occurs to generate a composite spectrum consistent with Cu(OH)(2) and (NH(4))(3)BTC species under humid conditions-the anticipated products of a copper(II) carboxylate reacted with limited ammonia. These species are not detected under dry conditions; however, reaction stoichiometry combined with XRD results suggests the partial formation of an indeterminate diammine copper (II) complex with some residual Cu(3)(BTC)(2) structure retained. Cu(II)-induced paramagnetic shifts exhibited by various species in (1)H and (13)C MAS NMR spectra are consistent with model compounds and previous literature. Although results show extensive ammonia capacity of Cu(3)(BTC)(2), much of the capacity is due to reaction with the structure itself, causing a permanent loss in porosity and structural integrity.

Adsorption equilibria are reported for isopropyl methylphosphonofluoridate (GB) on activated carbon at relative pressures (pi/ps) approaching 10-10 and temperatures between 30 and 100 °C. A novel desorption method and analytical apparatus employing purge-and-trap chromatography (PTC) were used to overcome the difficulties in quantifying the vapor phase at ultralow concentrations (

Current technology-based efforts are focusing on a nanotechnology approach to sorbent development for air purification applications. Metal-organic frameworks (MOFs) and zeolitic imidazolate frameworks (ZIFs) are two novel classes of materials that allow for specific functionalities to be designed directly into a porous framework. This report is the second in a series of summary reports based on the evaluation of samples from the University of California, Los Angeles. The samples evaluated in this report are a continuation of a baseline series of materials aimed at collecting design rules for future materials; results from this and the previous report will be used to create a second-generation of reactive MOFs and ZIFs for air purification applications. Testing of the novel materials included nitrogen isotherm data, water, and chloroethane adsorption equilibria, and ammonia, cyanogen chloride and sulfur dioxide breakthrough data.

This study considers the rate of reaction of GB, GD, VX, and HD on selected adsorbents measured using a solid phase NMR technique. The adsorbents in dry and humidified conditions are exposed to the chemical agents. The rate of disappearance of the starting chemical over time is used to calculate a reaction half time and first order reaction rate. The appearance of reaction product peaks are also noted. The half times for humid conditions are 10,000 min for some dry cases.

Metal–organic frameworks (MOFs) with metal–carboxylate bonds, including Cu-BTC (HKUST-1), Mg-MOF-74 (Mg/DOBDC), and UiO-66, have been shown to have varying degrees of water stability. The three MOFs in this study are three of the most highly studied MOFs in the literature. We investigate here how each MOF degrades at several temperature and humidity conditions over the course of 28 days. At conditions of 90% relative humidity (RH) and 25 °C, water uptake for Cu-BTC is shown to be higher than at 90% RH and 40 °C, causing the degradation of the inner structure of Cu-BTC to occur more readily at the lower temperature. However the external surfaces of Cu-BTC degrade more readily, as shown through SEM images, at conditions of 90% RH and 40 °C. Mg-MOF-74 has a nearly complete loss of surface area after just one day of exposure to each of the conditions studied, however the PXRD patterns show only a change in the [100] peak. We offer here a novel mechanism for the degradation of Mg-MOF-74, involving a 6-coordinate Mg intermediate, which leaves the 1-dimensional channels of Mg-MOF-74 intact. Furthermore, we conclude that UiO-66 is stable to each of the aging conditions for the full 28 days of this study.

In certain applications, PSA systems filter contaminants only under transient conditions. This paper presents both experimental and modeling work for the transient, non-isothermal behavior of PSA for air purification. The solutes considered include the refrigerant vapors R-22, R-11 and water vapor and adsorbents activated carbon and 13X molecular sieve. Simultaneous concentration samples at four in-bed locations, product and purge are recorded. In-bed temperature profiles are reported for complete cycles. The in-bed profiles are shown to provide a detailed representation of the progress of the concentration wave for the transient behavior. The non-isothermal effects are examined for several conditions including inert packing, non-adsorbing carrier and a varying purge to feed ratios. Chemical contaminant filtration is presented for strongly and weakly adsorbed vapors. Good agreement is achieved between the model simulation and the measured PSA data.

The design of a laboratory-scale pressure swing adsorption (PSA) system for air purification applications is described. Specific attention is provided to bed design, flow control, and feed generation systems. This apparatus is capable of automated, in-bed concentration, pressure and temperature measurements using computer control. Results are presented for some sample runs based on 150 SLPM of feed at three to four atmospheres of feed pressure.... Pressure profiles, Pressure swing adsorption, Experimental system, In-bed profiles, Laboratory scale, Concentration profiles.

The design of a PSA system for air purification applications is investigated with emphasis on experimental results. PSA experiments are performed using a test system consisting of a single adsorbable component, 1,1,2 trichloro, 1,2,2 trifluoroethane (CFC-113) and BPL carbon to examine the effects of (1) pressure ratio, (2) purge to product ratio, and (3) cycle time on system performance, where system performance is determined by the product air contaminant concentration. In-bed, vapor-phase concentration profiles are measured after a selected numbers of cycles in order to provide insight into the transient behavior of the system. An isothermal, trace component PSA model is developed which includes axial dispersion, an internal particle resistance, and non-linear adsorption equilibria. Results of the mathematical model are compared to experimental data.

Water vapor adsorption equilibria are measured for several unimipregnated and impregnated microporous carbons, including BPL, ASC, ASC-TEDA and a polymeric beaded carbon. Both the shape of the isotherms and the presence of hysteresis are characteristics of the capillary condensation mechanism. Sircar's isotherm expression, which incorporates capillary condensation with the Kelvin equation, has been modified to correlate the data for both adsorption and desorption. Two gamma distribution functions are required to represent the pore size distribution for the activated carbons while only one gamma distribution function is required to represent the pore size distribution for the polymeric beaded carbon. The pore distributions that result from correlating the isotherm data are consistent with the known structure of these adsorbents.

Water vapor adsorption and desorption equilibria was measured for BPL, ASC, ASC-TEDA, and CWS carbons, a polymeric beaded carbon and a foreign military filter carbon. The effect of temperature was considered over the range of 15-35 C. An isotherm expression was developed to describe capillary condensation on a particle with a disperse pore size distribution. This expression was fit to the measured data in order to compare the pore size distributions of the sample studies. A second isotherm expression was proposed based on a modification of the Antoine equation. This equation proved useful in obtaining a best fit correlation to the adsorption data. Humidity, Microporous activated carbons, Adsorption equilibria.