Different Adsorption Behaviors of Methane and Carbon Dioxide in the Isotypic Nanoporous Metal Terephthalates MIL-53 and MIL-47
A distinct step in the isotherm occurs during the adsorption of CO2 on MIL-53 at 304 K. Such behavior is neither observed during the adsorption of CH4 on MIL-53 nor during the adsorption on the isostructural MIL-47. This phenomenon seems to be due to a different mechanism than that of previous adsorption steps on MOF samples. It is suggested that a breathing behavior is induced in MIL-53 during CO2 adsorption.
Available from: Qibin Xia
- "A comparison of Figs. 2 and 3 showed that the CO 2 adsorption capacities of MIL-101 were higher than those of MIL-100(Fe) due to the higher pore volume and surface area of MIL-101(Cr). The maximum CO 2 uptakes of MIL-100(Fe) and MIL-101(Cr) were separately up to 15.9 and 21.0 mmol/g at 298 K and 25 bar, which were much higher than those of many other adsorbents at the similar condition, such as zeolite NaX , activated carbon Norit R1  and MIL-53(Cr)  "
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ABSTRACT: 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 CO2/N2 and CO2/CH4 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, CO2-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 CO2 working adsorption capacity and CO2/CH4 selectivity of MIL-100(Fe) due to formation of more adsorptive sites toward CO2, but it badly weakened those of MIL-101(Cr) due to H2O competitive adsorption. When relative humidity of feed stream increased from 0% to 50%, the CO2 capacity and CO2/CH4 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. CO2-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 H2O 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.
The Chemical Engineering Journal 06/2015; 270. DOI:10.1016/j.cej.2015.02.041 · 4.32 Impact Factor
- "Nanoporous carbon of high surface area has contributed to environmental, energy, and chemical technologies     . This is because nanoporous carbons have distinguished merits such as high electrical and thermal conductivities  , excellent water resistivity , and considerably high chemical stability except for that in an oxidative atmosphere, although the tunability of pore width is not sufficiently established yet. "
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ABSTRACT: Graphene monoliths made from graphene oxide colloids by unidirectional freeze-drying method were activated by typical activation processes of CO2 activation, chemical activation using ZnCl2 or H3PO4, and KOH activation. The porosity development of graphene monolith markedly depends on the activation method. The monoliths with highest surface area are obtained by the KOH activation method; only the KOH activation is effective for production of the graphene monolith of which surface area is in the range of 1760–2150 m2 g−1. The mechanism of the porosity development by KOH activation method is proposed. This work provides a promising route for the bottom-up design of pore width-tunable nanoporous carbons.
Carbon 09/2014; 76:220–231. DOI:10.1016/j.carbon.2014.04.071 · 6.20 Impact Factor
Available from: Jordi Toda
- "The size of the pores and the surface areas of MOFs were found to be larger than those determined for zeolites (microporous aluminosilicate minerals commonly used as commercial adsorbents). Furthermore, the framework flexibility of MOFs and the presence of unsaturated metal sites (undercoordinated open sites) has been suggested to have a vital role in their interaction with some molecules.  These are the main reasons for the growing scientific interest in MOFs since the first example of this class of porous material was reported. "
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ABSTRACT: This chapter reviews recent applications of density functional theory (DFT) based methods in the study of the interaction of small gaseous molecules with metal nanoparticles, metal surfaces, and porous or biological materials and applications in the study of chemical reactions at catalytic sites of transition metals or enzymes. Focus is given to the interaction of small molecules, e.g. H2O, O2, CO, CO2, etc., with the scaffold atoms of metal organic frameworks (MOF) or with zeolites, in the field of gas adsorption, or with the exposed atoms on transition metal surfaces or nanoparticles, in the field of heterogeneous catalysis, and to the interaction of small organic molecules with the capacity to inhibit a catalytic cysteine of the Malaria’s parasite, in the field of drug design. The roles of under-coordinated atoms on the strength of the interaction and of the type of the exchange-correlation functional considered for the calculations are analyzed. Finally, recent successes of the consideration of DFT based approaches to study, with atomic detail, the reactions of such molecules on these materials are also reviewed.
Density Functional Theory: Principles, Applications and Analysis, 03/2013: chapter Density functional treatment of interactions and chemical reactions at surfaces: pages Density functional treatment of interactions and chemical reactions at surfaces; Nova Science Publishers, Inc..
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