Different Adsorption Behaviors of Methane and Carbon Dioxide in the Isotypic Nanoporous Metal Terephthalates MIL-53 and MIL-47

Aix-Marseille Université, Marsiglia, Provence-Alpes-Côte d'Azur, France
Journal of the American Chemical Society (Impact Factor: 12.11). 11/2005; 127(39):13519-21. DOI: 10.1021/ja054668v
Source: PubMed


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.

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    • "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 [31], activated carbon Norit R1 [32] and MIL-53(Cr) [33] "
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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
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    • "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.[87] [88] 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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