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The separation of n‐alkanes from their branched isomers is vitally important to improve octane rating of gasoline. To facilitate mass transfer, adsorptive separation is usually operated under high temperatures in industry, which require considerable energy. Herein, we present a kind of dynamic pillar‐layered MOF that exhibits self‐adjustable structure and pore space, a behavior induced by guest molecules. A combination of the flexibility of the framework with the commensurate adsorption for n‐hexane results in exceptional performance in separating hexane isomers. More significantly, lower temperature prompts the guest molecules to open the dynamic pores, which may provide a new perspective for optimized separation performance at lower temperatures with less energy consumption. [ABSTRACT FROM AUTHOR]

The separation of n‐alkanes from their branched isomers is vitally important to improve octane rating of gasoline. To facilitate mass transfer, adsorptive separation is usually operated under high temperatures in industry, which require considerable energy. Herein, we present a kind of dynamic pillar‐layered MOF that exhibits self‐adjustable structure and pore space, a behavior induced by guest molecules. A combination of the flexibility of the framework with the commensurate adsorption for n‐hexane results in exceptional performance in separating hexane isomers. More significantly, lower temperature prompts the guest molecules to open the dynamic pores, which may provide a new perspective for optimized separation performance at lower temperatures with less energy consumption. [ABSTRACT FROM AUTHOR]

Novel PEI impregnated ZIF-8 (PEI@ZIF-8) composites, with characteristic of water vapor enhanced adsorption property, were synthesized for CO 2 /N 2 separation, and then characterized by N 2 adsorption, PXRD, IR and TG. CO 2 and N 2 isotherms were measured by static adsorption, and the breakthrough curves of CO 2 /N 2 mixture v CO 2 / v N 2 of 1 / 1 through the fixed bed of the composites were determined in presence of water vapor. Results showed that CO 2 working capacity and CO 2 /N 2 selectivity of as-synthesized PEI@ZIF-8 at 338 K were up to 1.61 mmol/g and 62, being 6.2 and 27 times of those of ZIF-8 at 303 K, respectively. PEI@ZIF-8 is thermally stable until 450 K. More importantly, it was found that the presence of water vapor in feed stream further enhanced the CO 2 capacity and CO 2 /N 2 selectivity of PEI@ZIF-8, which separately reached 1.99 mmol/g and 89.3 at RH of 55% and 338 K, having increases of 23.6% and 44% in comparison with those under dry condition. The enhancement could be attributed to the synergy action mechanism of water steam and PEI. Calculation by density functional theory revealed that the presence of water vapor resulted in the formation of bicarbonate, and thus promoted more CO 2 molecules to be adsorbed on PEI@ZIF-8. This water vapor enhanced action mechanism can be applied to design rationally more efficient adsorbents for CO 2 capture under realistic situation where water vapor is always present. [ABSTRACT FROM AUTHOR]

It is well-known that water vapor is omnipresent. It always has strong influence on adsorption performances of various applied porous materials in realistic situations. Adsorption behaviors of CO 2 /N 2 and CO 2 /CH 4 binary mixtures over MIL-100(Fe) and MIL-101(Cr) were investigated in presence and absence of water vapor in feed stream by static adsorption, fixed bed experiments, CO 2 -TPD technique and in situ FTIR analysis. Interesting and unexpected results were obtained. It was found that the presence of water vapor significantly enhanced the CO 2 working adsorption capacity and CO 2 /CH 4 selectivity of MIL-100(Fe) due to formation of more adsorptive sites toward CO 2 , but it badly weakened those of MIL-101(Cr) due to H 2 O competitive adsorption. When relative humidity of feed stream increased from 0% to 50%, the CO 2 capacity and CO 2 /CH 4 selectivity of MIL-100(Fe) increased by 150% and 200%, respectively, and in contrast to that, those of MIL-101(Cr) decreased by 44% and 18% respectively. CO 2 -TPD curve of MIL-100(Fe) exhibited only one desorption peak in dry atmosphere, while two peaks in humid atmosphere, suggesting that new type of alkaline adsorptive sites were formed due to H 2 O dissociation on MIL-100(Fe), which was confirmed by in situ FTIR analysis. This water vapor-enhanced mechanism is interesting, and is worthy of further exploiting for obtaining novel adsorbents. [ABSTRACT FROM AUTHOR]

• The large-scale synthesis of H 4 abtc (180 g scale) and Y-abtc (100 g scale) in high yields. • Breakthrough experiments on binary mixtures of propane/propylene at the 100 g scale. • Polymer grade propylene purity achieved using Y-abtc at 100 g scale. • Retained performance of Y-abtc at large scale demonstrating its potential for real world applications. Olefin/Paraffin separation, especially propylene purification from propane, is of extreme commercial importance as it produces chemical feedstock for synthetic plastics such as polypropylene. As an alternative to cryogenic distillation commonly used to purify these mixtures, the use of solid porous materials for adsorptive separation offers a more energetically efficient route. Metal-Organic Frameworks (MOFs) have shown great promise as adsorptive separation candidates in recent years. However, reports of these materials for the purification of C3 hydrocarbons exclusively provide insight of their performance in small scale laboratory settings. Single component isotherms and breakthrough curves are typically tested in the milligrams to gram scale. Herein, we present a scale-up, one-pot synthesis of a robust MOF with high propylene/propane selectivity. The organic linker 3,3′,5,5′-azobenzene-tetracarboxylic acid (H 4 abtc) and its yttrium-based MOF, Y-abtc, are both synthesized at the hundred-gram scale. Furthermore, we perform large-scale breakthrough experiments at the same scale. Our results show that Y-abtc samples synthesized from the one-pot 100 g scale reactions retain high crystallinity and size-exclusion based mechanism for the separation of propane/propylene mixtures. The same polymer-grade purity of propylene (>99.5%) is achieved as in the case of small scale (∼1 g) experiments. [ABSTRACT FROM AUTHOR]

Adsorption equilibrium and kinetics of 1,2-dichloroethane on a chromium-based metal-organic framework MIL-101 were studied. Desorption activation energies of 1,2-dichloroethane on the MIL-101 were measured using temperature program desorption (TPD) experiments. Results showed that the adsorption capacity of the MIL-101 for 1,2-dichloroethane is 19 mmol/g at 288 K, being much higher than those of some activated carbon, zeolite, and MWCNTs. The isotherms of 1,2-dichloroethane were well fitted by the Langmuir equation. The isosteric heat and diffusion coefficients of 1,2-dichloroethane adsorption on the MIL-101 were separately within the range of 42.0–61.6 kJ/mol and range of 0.854–2.246 × 10−10 cm2/s. TPD spectra exhibited two types of adsorption sites on the MIL-101 with desorption activation energy of 48.6 and 87.6 kJ/mol separately. Multiple recycle runs of 1,2-dichloroethane adsorption-desorption at 298 K (10 mbar for adsorption and 0.05 mbar for desorption) showed the 1,2-dichloroethane adsorption on the MIL-101 is highly reversible, and desorption efficiency is up to 98.42%. [ABSTRACT FROM PUBLISHER]

The adsorption and desorption of toluene on metal-organic frameworks HKUST-1 and MIL-101 were studied. The adsorption isotherms and kinetic curves of toluene on HKUST-1 and MIL-101 were separately measured by gravimetric method. Temperature-programmed desorption experiments were carried out for estimating the interaction of toluene with the surfaces of HKUST-1 and MIL-101. Our experimental results showed that the isotherms of toluene on the adsorbents were well fitted by the Langmuir-Freundlich equation. The maximum amount of toluene adsorbed on MIL-101 was 15.1 mmol/g, which was much higher than that adsorbed on HKUST-1 (6.6 mmol/g). The high adsorption capacity of MIL-101 can be attributed to its higher surface area. However, the isotherm of toluene at P/P0 < 0.09 on HKUST-1 was much higher than that on MIL-101 owing to the smaller pore size of HKUST-1. It is suggested that HKUST-1 had better adsorption performance than MIL-101 at low concentration of volatile organic compounds. The desorption activation energies, Ed, of toluene on HKUST-1 and MIL-101 were 43.8 and 30.2 kJ/mol, respectively, meaning that the interaction of toluene with HKUST-1 was stronger than that with MIL-101. In addition, the diffusion coefficient of toluene within HKUST-1 was smaller than that within MIL-101. Results of thermal desorption experiments showed that the desorption efficiency of toluene from HKUST-1 and MIL-101 can separately reach above 93% and nearly 100% at 393 K, respectively. [ABSTRACT FROM AUTHOR]

Abstract: The imidazolate framework ZIF-8 samples were modified separately by using ammonia impregnation and thermal treatment in atmosphere of N2 or H2 in order to improve its adsorption property toward CO2, and the modified samples A-ZIF-8, N-ZIF-8 and H-ZIF-8 were correspondingly available. The modified ZIF-8 samples were characterized, and the surface chemical properties of the ZIF-8 samples were determined separately by FTIR, CO2-TPD, NH3-TPD and H2O-TPD. The isotherms of CO2 on the modified ZIF-8 samples were measured. Results showed that after surface modification, the total amounts of basicity of the modified samples significantly increased, and followed the order: A-ZIF-8>H-ZIF-8>N-ZIF-8>O-ZIF-8. The uptakes of CO2 increased proportionally with the basic groups on the surfaces of the ZIF-8 samples due to CO2 being an acidic molecule. As a consequence of that, the CO2 adsorption capacity of the samples followed the order: A-ZIF-8>H-ZIF-8>N-ZIF-8>O-ZIF-8. The amount adsorbed of CO2 on the modified ZIF-8 sample by ammonia impregnation is the highest, having an increase. [Copyright &y& Elsevier]

This work investigates the adsorptionof organosulfur compoundsin model fuels over metal–organic frameworks (MOFs) using acombined experimental/computational approach. Adsorption isothermsof three MOFs, MIL-101(Cr), MIL-100(Fe), and Cu-BTC, follow the Langmuirisotherm models, and Cu-BTC shows the highest adsorption capacityfor both dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT),ascribing to the highest density of adsorption sites and fairly strongadsorption sites on Cu-BTC. Experimental results show adsorption selectivityof various compounds in model fuels follows the order of quinoline(Qu) > indole (In) > DBT > 4,6-DMDBT > naphthalene (Nap),which isconsistent with the order of calculated binding energies. Adsorptioncapacities of thiophenic compounds decrease significantly with theintroduction of Qu, In, or water due to their strong competitive adsorptionsover the coordinatively unsaturated Cu sites on Cu-BTC. The bindingenergies of Qu, In, H2O, and DBT are calculated as −56.04,−41.01, −50.27, and −27.52 kJ/mol, respectively.The experimental and computational results together suggest that theadsorption strength of thiophenic compounds over Cu-BTC is dominatedby the interaction of both the conjugated π system (π-M)and the lone pair of electrons on sulfur atom (σ-M) of thiophenes,with the coordinatively unsaturated sites (CUS) on Cu-BTC. Alkyl groupson 4- and/or 6-positions of thiophenic compounds function as botheletron donor to increase π-M interaction and steric inhibitorto decrease σ-M interaction. MOFs with strong and highly denseCUS can be promising materials for ADS of fuels. [ABSTRACT FROM AUTHOR]