Framework-Flexibility Driven Selective Sorption of p-Xylene over Other Isomers by a Dynamic Metal-Organic Framework (original) (raw)
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Separation of Xylene Isomers through Multiple Metal Site Interactions in Metal-Organic Frameworks
Journal of the American Chemical Society, 2018
Purification of the Calkylaromatics o-xylene, m-xylene, p-xylene, and ethylbenzene remains among the most challenging industrial separations, owing to the similar shapes, boiling points, and polarities of these molecules. Herein, we report the evaluation of the metal-organic frameworks Co(dobdc) (dobdc= 2,5-dioxido-1,4-benzenedicarboxylate) and Co(m-dobdc) (m-dobdc= 4,6-dioxido-1,3-benzenedicarboxylate) for the sepa-ration of xylene isomers using single-component adsorption isotherms and multi-component breakthrough measurements. Remarkably, Co(dobdc) distinguishes among all four molecules, with binding affinities that follow the trend o-xylene > ethylbenzene > m-xylene > p-xylene. Multi-component liquid-phase adsorption measurements further demonstrate that Co(dobdc) maintains this selectivity over a wide range of concentrations. Structural characterization by single-crystal X-ray diffraction reveals that both frameworks facilitate the separation through the extent of inte...
Inorganic chemistry, 2015
The separation of styrene and ethylbenzene mixtures is industrially important and is currently performed in highly energy-intensive vacuum distillation columns. The primary objective of our investigation is to offer an energy-efficient alternative for selective adsorption of styrene by a flexible metal-organic framework, DynaMOF-100. The structural transformation of DynaMOF-100 is specifically triggered on inclusion of styrene within the framework; this structural transformation is reversible. The styrene/ethylbenzene adsorption selectivity, originated as an outcome of the framework flexibility, is found to be much superior to the only two MOFs yet reported, serving styrene/ethylbenzene separation purpose.
The Journal of Physical Chemistry C, 2009
Vapor-phase adsorption of the C8 alkylaromatic components p-xylene (p-x), m-xylene (m-x), o-xylene (o-x), and ethylbenzene (eb) on the three-dimensional microporous metal-organic framework (MOF) Zn(BDC)-(Dabco) 0.5 (BDC) 1,4-benzenedicarboxylate, Dabco) 1,4-diazabicyclo[2.2.2]octane) was investigated. Singleand multicomponent fixed-bed experiments were carried out at temperatures ranging from 125 to 175°C and total hydrocarbon pressures up to 0.10 bar. At high pressure, the adsorption capacity for all the components varies from 35 to 26 g/100 g ads at 125 and 175°C. Henry's constants are slightly different for all C8 alkylaromatics, except for o-xylene, which is significantly higher. The adsorption enthalpies at zero coverage for the different isomers ranges from 77.40 (eb) to 79.84 kJ/mol (o-x), indicating that the C8 alkylaromatics have comparable interactions with the framework at the low coverage. On the basis of binary and quaternary breakthrough experiments performed at different hydrocarbon pressures and temperatures, MOF Zn(BDC)(Dabco) 0.5 was realized for the efficient and feasible separation of o-xylene from other C8 alkylaromatic components with the selectivity up to 1.88 because of the stronger interactions between o-xylene molecules and the framework and their differential pore-filling and molecular-packing effects confined within nanopores of MOFs.
A Complete Separation of Hexane Isomers by a Functionalized Flexible Metal Organic Framework
Advanced Functional Materials, 2014
such as the mono-branched hexane isomer 3MP are usually still present and contribute to decrease the performance of the process. To overcome this drawback, there is a crucial need to search for alternative porous solids able to more selectively adsorb di-branched compounds such as the 22DMB from the mono-branched 3MP and linear nHEX.
Metal–organic frameworks (MOFs) or porous coordination polymers (PCPs) are defined as crystalline, open, coordination network architectures with potential voids. They have drawn momentous attention across several crossroads of material chemistry since their discovery, owing to an exciting plethora of application-oriented footprints left by this class of supramolecular network solids. The unmatched aspect of tunable coordination nanospace arising from the countless choice of pre-functionalized organic struts pertaining to varying lengths alongside multivariate coordination geometries/oxidation states of the metal nodes, bestows a distinct chemical tailorability facet to this class of porous materials. Amidst the two-decade long attention dedicated to the adsorption–governed purification of gases, the MOF literature has substantially expanded its horizon into the manifestation of industrially relevant liquid mixtures' adsorptive separation–driven purification. Such chemical separation phenomena categorically encompasses high importance to the manufacturing and processing industry sectors, apart from the fundamental scientific pursuit of discovering novel physicochemical principles. Aimed at the energy-economic preparation of pure industrial feedstocks and their consequent usage as end products, structure–property correlations pursued in the alleys of coordination chemistry has led to major advancements in a number of critical separation frontiers, inclusive of biofuels (alcohol/water), diverse hydrocarbon mixtures, and chiral species. This comprehensive review summarizes the topical developments accrued in the field of MOF based liquid mixtures' adsorptive separation phenomena, structure– selectivity relationships as well as the associated plausible mechanisms substantiating such behavior.
Flexibility in Metal–Organic Frameworks: A Basic Understanding
Catalysts, 2019
Much has been written about the fundamental aspects of the metal–organic frameworks (MOFs). Still, details concerning the MOFs with structural flexibility are not comprehensively understood. However, a dramatic increase in research activities concerning rigid MOFs over the years has brought deeper levels of understanding for their properties and applications. Nonetheless, robustness and flexibility of such smart frameworks are intriguing for different research areas such as catalysis, adsorption, etc. This manuscript overviews the different aspects of framework flexibility. The review has touched lightly on several ideas and proposals, which have been demonstrated within the selected examples to provide a logical basis to obtain a fundamental understanding of their synthesis and behavior to external stimuli.
Review Flexibility in Metal-Organic Frameworks: A Basic Understanding
Catalysts 2019, 9, 512, 2019
Much has been written about the fundamental aspects of the metal-organic frameworks (MOFs). Still, details concerning the MOFs with structural flexibility are not comprehensively understood. However, a dramatic increase in research activities concerning rigid MOFs over the years has brought deeper levels of understanding for their properties and applications. Nonetheless, robustness and flexibility of such smart frameworks are intriguing for different research areas such as catalysis, adsorption, etc. This manuscript overviews the different aspects of framework flexibility. The review has touched lightly on several ideas and proposals, which have been demonstrated within the selected examples to provide a logical basis to obtain a fundamental understanding of their synthesis and behavior to external stimuli.
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This work investigates the morphological control of the anisotropic [Zn2(NDC)2(DABCO)]n MOF (Metal organic framework) and the subsequent adsorption characteristics for CO2/CH4 gas separation. Morphology of the MOF crystals is controlled by the use of modulators. The addition of acetic acid or pyridine successfully produce rod or plate morphologies, respectively, with each morphology possessing a different major surface pore aperture. Single-component equilibrium and kinetic adsorption data for CO2 and CH4 were collected. Equilibrium analysis indicates a slight selectivity towards CO2 whereas kinetic data unexpectedly shows lower diffusion time constants for CO2 compared to CH4. Mass transfer resistances on each species is discussed. Finally, a coating technique termed solution shearing is used to orient different morphologies on substrates as a film. An increase in film orientation is observed for the rod morphology, indicating that this MOF morphology is a promising candidate to cr...