Showing papers by "Praveen K. Thallapally published in 2017"
TL;DR: In this paper, a nickel isonicotinate based ultramicroporous MOF, 1 [Ni-(4PyC)2·DMF], has been proposed for postcombustion CO2 capture.
Abstract: Metal–organic frameworks (MOFs) have attracted significant attention as solid sorbents in gas separation processes for low-energy postcombustion CO2 capture. The parasitic energy (PE) has been put forward as a holistic parameter that measures how energy efficient (and therefore cost-effective) the CO2 capture process will be using the material. In this work, we present a nickel isonicotinate based ultramicroporous MOF, 1 [Ni-(4PyC)2·DMF], that has the lowest PE for postcombustion CO2 capture reported to date. We calculate a PE of 655 kJ/kg CO2, which is lower than that of the best performing material previously reported, Mg-MOF-74. Further, 1 exhibits exceptional hydrolytic stability with the CO2 adsorption isotherm being unchanged following 7 days of steam-treatment (>85% RH) or 6 months of exposure to the atmosphere. The diffusion coefficient of CO2 in 1 is also 2 orders of magnitude higher than in zeolites currently used in industrial scrubbers. Breakthrough experiments show that 1 only loses 7% of its...
110 citations
TL;DR: In this article, the effect of subtle structural changes upon the gas sorption behavior of two "SIFSIX-3-M" pillared square grid frameworks, namely SIFS6-3M (M = Ni, Fe), was investigated.
Abstract: Dynamic and flexible metal-organic frameworks (MOFs) that respond to external stimuli, such as stress, light, heat, and the presence of guest molecules, hold promise for applications in chemical sensing, drug delivery, gas separations, and catalysis. A greater understanding of the relationship between flexible constituents in MOFs and gas adsorption may enable the rational design of MOFs with dynamic moieties and stimuli-responsive behavior. Here, we detail the effect of subtle structural changes upon the gas sorption behavior of two "SIFSIX" pillared square grid frameworks, namely SIFSIX-3-M (M = Ni, Fe). We observe a pronounced inflection in the Xe adsorption isotherm in the Ni variant. With evidence from X-ray diffraction studies, density functional theory, and molecular simulations, we attribute the inflection to a disordered to ordered transition of the rotational configurations of the pyrazine rings induced by sorbate-sorbent interactions. We also address the effect of cage size, temperature, and sorbate on the guest-induced ring rotation and the adsorption isotherms. The absence of an inflection in the Xe adsorption isotherm in SIFSIX-3-Fe and in the Kr, N2, and CO2 adsorption isotherms in SIFSIX-3-Ni suggest that the inflection is highly sensitive to the match between the size of the cage and the guest molecule.
101 citations
TL;DR: In this paper, a prototypical type of metal organic framework, zeolitic imidazolate framework-8 (ZIF-8), in membrane form, can effectively separate Kr/Xe gas mixtures at industrially relevant compositions.
Abstract: Herein, we demonstrate that a prototypical type of metal organic framework, zeolitic imidazolate framework-8 (ZIF-8), in membrane form, can effectively separate Kr/Xe gas mixtures at industrially relevant compositions. The best membranes separated Kr/Xe mixtures with average Kr permeances as high as 1.5 × 10–8 ± 0.2 mol/m2 s Pa and average separation selectivities of 14.2 ± 1.9 for molar feed compositions corresponding to Kr/Xe ratio encountered typically in air. Molecular sieving, competitive adsorption, and differences in diffusivities were identified as the prevailing separation mechanisms. These membranes potentially represent a less-energy-intensive alternative to cryogenic distillation, which is the benchmark technology used to separate this challenging gas mixture. To our best knowledge, this is the first example of any metal organic membrane composition displaying separation ability for Kr/Xe gas mixtures.
80 citations
TL;DR: In this paper, AlPO-18 membranes can separate N2/CH4 gas mixtures at unprecedented N2 permeances, achieving a separation selectivity as high as 4.6.
Abstract: Herein we demonstrate that AlPO-18 membranes can separate N2/CH4 gas mixtures at unprecedented N2 permeances. The best membranes separated N2/CH4 mixtures with N2 permeances as high as 3076 GPU and separation selectivities as high as 4.6. Gas mixture separation data, N2 and CH4 adsorption isotherms, ideal adsorbed solution theory (IAST), and breakthrough experiments were collected to understand the separation mechanisms. Competitive adsorption and differences in diffusivities were identified as the prevailing separation mechanisms. Differences in diffusivity played a more dominant role than the competitive adsorption, and led to nitrogen selective membranes.
47 citations
TL;DR: Structural analysis of the core-shell particles suggests that the distribution of MOF precursors inside the magnetic core resulted in the oxidation of the iron oxide core.
Abstract: The magnetic susceptibility of synthesized magnetite (Fe3O4) microspheres was found to decline after the growth of a metal–organic framework (MOF) shell on the magnetite core. Detailed structural analysis of the core–shell particles using scanning electron microscopy, transmission electron microscopy, atom probe tomography, and57Fe–Mossbauer spectroscopy suggests that the distribution of MOF precursors inside the magnetic core resulted in the oxidation of the iron oxide core.
43 citations
TL;DR: In this paper, a series of microporous metal-organic frameworks (MOFs) constructed by using a V-shaped linker, 4,4′-sulfonyldibenzoic acid, were evaluated for their Xe gas adsorption properties.
Abstract: A series of microporous metal–organic frameworks (MOFs) constructed by using a V-shaped linker, 4,4′-sulfonyldibenzoic acid, were evaluated for their Xe gas adsorption properties. In particular, a cadmium-based MOF exhibits noteworthy Xe adsorption and separation properties in the presence of other gases under nuclear reprocessing conditions. The outstanding Xe adsorption capacity was attributed to the close pore size matching of the MOF with the kinetic diameter of the Xe atom.
40 citations
TL;DR: The in situ synchrotron measurements suggest that Xe is occupies the small pockets of PCN-12 compared to unsaturated metal centers (UMCs), and Computational modeling of adsorption further supports the experimental observation of Xe binding sites in PCn-12.
Abstract: Xenon is known to be a very efficient anesthetic gas, but its cost prohibits the wider use in medical industry and other potential applications. It has been shown that Xe recovery and recycling from anesthetic gas mixtures can significantly reduce its cost as anesthetic. The current technology uses series of adsorbent columns followed by low-temperature distillation to recover Xe; this method is expensive to use in medical facilities. Herein, we propose a much simpler and more efficient system to recover and recycle Xe from exhaled anesthetic gas mixtures at room temperature using metal-organic frameworks (MOFs). Among the MOFs tested, PCN-12 exhibits unprecedented performance with high Xe capacity and Xe/O2 , Xe/N2 and Xe/CO2 selectivity at room temperature. The in situ synchrotron measurements suggest that Xe is occupies the small pockets of PCN-12 compared to unsaturated metal centers (UMCs). Computational modeling of adsorption further supports our experimental observation of Xe binding sites in PCN-12.
35 citations
TL;DR: The higher formal charge of molybdenum, Mo4+, in MoSx versus that of antimony, Sb3+, in SbSx coupled with its larger atomic size could induce higher polarizability in theMoSx framework and therefore higher Xe/Kr selectivity.
Abstract: High-surface-area molybdenum sulfide (MoSx) and antimony sulfide (SbSx) chalcogels were studied for Xe/Kr gas separation. The intrinsic soft Lewis basic character of the chalcogel framework is a unique property among the large family of porous materials and lends itself to a potential new approach toward the selective separation of Xe over Kr. Among these chalcogels, MoSx shows the highest Xe and Kr uptake, reaching 0.69 mmol g–1 (1.05 mmol cm–3) and 0.28 mmol g–1 (0.42 mmol cm–3) respectively, at 273 K and 1 bar. The corresponding isosteric heat of adsorption at zero coverage (Qst0) is 22.8 and 18.6 kJ mol–1 and both are the highest among the selected chalcogels. The IAST (10:90) Xe/Kr selectivity at 273 K for MoSx is 6.0, whereas for SbSx chalcogels, it varies in the range 2.0–2.8. The higher formal charge of molybdenum, Mo4+, in MoSx versus that of antimony, Sb3+, in SbSx coupled with its larger atomic size could induce higher polarizability in the MoSx framework and therefore higher Xe/Kr selectivity.
15 citations
Patent•
09 Jun 2017
TL;DR: In this article, the authors describe methods and materials for the selective capture and storage of preselected materials from gas streams using metal organic framework (MOF) materials. But they do not discuss the use of MOF for the storage of these materials.
Abstract: Methods and materials for the selective capture and storage of preselected materials from gas streams using metal organic framework (MOF) materials are described. In various embodiments preselected target material gases could include noble gasses such as Kr, Xe, Rn, Arultramicro to mesopore frameworks for selective separation and storage of noble gases, other gasses such as I 2 or other particular isotopes either naturally occurring or man-made, or another preselected gas capture material such as a target material for legal, regulatory or treaty compliance, or a preselected material from a particular process such as a cleaning or etching agent from semiconducting or microelectronic manufacture, or a portion of an anesthetic gas such as nitrous oxide, isoflurane, sevoflurane or a fluorinated ethers.
4 citations