Atomistic grand canonical Monte Carlo simulations were performed to understand the interplay of factors (pore size, heat of adsorption, open metal sites, electrostatics, and ligand functionalization) ...contributing to adsorption of CO2, CO, and N2 in MOFs. Four MOFsIRMOF-1, IRMOF-3, Cu-BTC, and Zn2bdc2dabcowere chosen for comparison. Binary mixtures (CO2/CO) and (CO2/N2) containing 5%, 50%, and 95% CO2 were examined. CO2 is preferentially adsorbed over CO and N2 in all MOFs. Cu-BTC displays higher selectivities for CO2 over CO at lower pressures and CO2 over N2 at all pressures for all mixtures due to the increase in electrostatic interactions of CO2 with the exposed copper sites. However, IRMOF-3 shows surprisingly high selectivities for CO2 over CO for 50% and 95% mixtures at higher pressures due to the presence of amine-functionalized groups and high pore volume. CO2 selectivities increase with increasing CO2 concentration in the gas mixtures at total pressures above 5 bar. On the basis of the results obtained, it can be concluded that construction of smaller pore size MOFs relative to sorbate size with embedded open metal sites or functionalized groups can lead to greater enhancement of these adsorption separation systems.
Atomistic grand canonical Monte Carlo simulations were performed in this work to investigate the role of open copper sites of Cu-BTC in affecting the separation of carbon monoxide from binary ...mixtures containing methane, nitrogen, or hydrogen. Mixtures containing 5%, 50%, or 95% CO were examined. The simulations show that electrostatic interactions between the CO dipole and the partial charges on the metal−organic framework (MOF) atoms dominate the adsorption mechanism. The binary simulations show that Cu-BTC is quite selective for CO over hydrogen and nitrogen for all three mixture compositions at 298 K. The removal of CO from a 5% mixture with methane is slightly enhanced by the electrostatic interactions of CO with the copper sites. However, the pore space of Cu-BTC is large enough to accommodate both molecules at their pure-component loadings, and in general, Cu-BTC exhibits no significant selectivity for CO over methane for the equimolar and 95% mixtures. On the basis of the pure-component and low-concentration behavior of CO, the results indicate that MOFs with open metal sites have the potential for enhancing adsorption separations of molecules of differing polarities, but the pore size relative to the sorbate size will also play a significant role.
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► {Cu3(BTB)2(H2O)3⋅(DMF)9(H2O)2} MOF with very good structural properties obtained. ► Gas sorption of CO2, CH4, and N2 as a single-gas on the MOF-14 material was studied. ► Adsorption ...of CO2/CH4 and CO2/N2 gas mixtures on obtained copper MOF was presented. ► We report a water-exposure influence on a copper carboxylate framework MOF-14.
Metal–organic frameworks (MOFs) are attractive microporous materials for adsorption separations due to their extraordinary structures and impressive high surface areas. Catenation, or framework interpenetration, can significantly impact the crystal stability and improve the adsorption interactions. This interesting approach was used to obtain {Cu3(BTB)2(H2O)3⋅(DMF)9(H2O)2} (MOF-14) as a microporous material with a high surface area and large pore volume, which are desirable parameters for adsorption applications. Here, we report a detailed study of this catenated material with its gas adsorption properties. The potential for adsorption separations is evaluated by measuring pure-component adsorption isotherms for carbon dioxide, methane, and nitrogen. The Ideal Adsorbed Solution Theory (IAST) was used to evaluate adsorption selectivities of MOF-14 for CO2/CH4 and CO2/N2 equimolar mixtures. In addition, water adsorption and the impact of exposure on structural degradation are reported. Compared to other open-metal site MOFs, MOF-14 adsorbs significantly less water. This interwoven MOF is a promising competitor to other MOF materials in the gas separation field due to low interactions with water and high selectivity for CO2 over N2.
Three porous metal–organic frameworks {Ni(H2BTTB)·(H2O)2·(DIOX)2} n (1), {Zn(H2BTTB)·(DEF)3·(H2O)2} n (2), and {Mg(H2BTTB)·(C2H5OH)2·(DEF)4} n (3) based on the ...4,4′,4″,4‴-benzene-1,2,4,5-tetrayltetrabenzoic acid (H4BTTB) ligand have been synthesized under solvothermal conditions (DIOX = dioxane). These three MOFs show structural diversities: compound 1 is a two-dimensional (2D) grid layer, compound 2 is a 2-fold interpenetrated 3D framework with a pillared-layer structure, and compound 3 is a noninterpenetrated 3D framework with a (4, 4)-connected binodal net. Compound 1 and compound 2 have BET surface areas of 391 and 447 m2/g, respectively; however, the surface area of compound 3 cannot be experimentally determined. All three MOFs have a higher adsorption preference for CO2 over N2 and CH4. Ideal adsorbed solution theory was used to estimate binary adsorption selectivities. Compound 2 shows the highest capacity for all three gases, whereas compound 1 shows the highest selectivity for CO2 over CH4 and N2. Compound 1 exhibits a selectivity of ∼30 for CO2 over N2 in equimolar mixtures.
•Developed NH3 sorbent material for on-board purification of hydrogen.•Metal chloride impregnated super-activated carbon is thermally regenerable.•NH3 adsorption isotherm equation includes MnCl2 ...ammoniate formation.
The application of chemical hydrides (e.g. ammonia borane) and amide-based hydrogen storage materials would benefit from an effective means to remove ammonia, which is an impurity that is detrimental to the performance of a PEM fuel cell. One option is to adsorb ammonia on a sorbent with high capacity that would also be regenerable. Such a sorbent was developed by impregnating super activated carbon with metal chlorides (MgCl2, ZnCl2, MnCl2). The sorbent was characterized through static and dynamic adsorption experiments. It was shown to have a good cyclic stability. The filter weight, volume and pressure drop appears reasonable for an onboard vehicle application when it would be replaced/regenerated every 1800 miles, similar to an oil change.
Chiral nanotube: A flexible porous homochiral SrSi2 framework of two types of single‐stranded helical nanotubes is presented (see structure). The CuI ions in the framework can be oxidized to CuII ...through single‐crystal‐to‐single‐crystal transformation forming a new, topologically equivalent phase, accompanied by an expansion in the unit cell volume of 12.51 %.
A method was developed for sizing the particulate filter that can be used inside a sorption-based onboard hydrogen storage system for light-duty vehicles. The method is based on a trade-off between ...the pressure drop across the particulate filter (during the fill of the H
2
storage tank or during its discharge while driving) and the effect of this pressure drop on the usable amount of H
2
gas from the H
2
storage system. The permeability and filtration efficiency of the particulate filters (in the absence and presence of MOF-5 particulates) was quantified in this study, with an emphasis on meeting DOE’s H
2
purity requirements.
A method was developed for sizing the particulate filter that can be used inside a sorption-based onboard hydrogen storage system for light-duty vehicles. The method is based on a trade-off between ...the pressure drop across the particulate filter (during the fill of the H sub(2) storage tank or during its discharge while driving) and the effect of this pressure drop on the usable amount of H sub(2) gas from the H sub(2) storage system. The permeability and filtration efficiency of the particulate filters (in the absence and presence of MOF-5 particulates) was quantified in this study, with an emphasis on meeting DOE's H sub(2) purity requirements.
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