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.
"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. "
[Show abstract][Hide abstract] 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..
"Conventional commercial technologies for CO 2 removal are not cost-effective and they suffer from serious energy penalties, and yield poor absorption efficiencies. Therefore development of stable and recyclable solid adsorbents that could adsorb CO 2 efficiently and contribute to the process economy would be highly desired          . A variety of solid materials that readily adsorb CO 2 are available , including metal oxides and mixed metal oxides   , high-surface-area porous materials, such as zeolites    , carbon , metal-organic frameworks (MOFs)   , organosilica, and surface-modified silica   . "
[Show abstract][Hide abstract] ABSTRACT: Solid adsorbents comprising 50, 70, and 90 wt.% heteropolyacid Fe2.0SiW12O40 (Fe–HPA) and mesoporous cellular foams (MCFs) have been synthesized by wetting impregnation. The adsorbents were characterized by various physicochemical, thermal and spectral techniques and the CO2 adsorption capacity of the adsorbents were investigated. The structure of Fe–HPA on the surface of the support was confirmed by TEM, SAXS, XRD, SEM, FTIR, 29Si MAS NMR, and XPS. XPS of the Fe 2p3/2, 2p1/2, 3p and W 4f7/2, 4f5/2, 4d5/2, 4d3/2 confirmed the presence of typical Fe(2 +) and W(6 +) in the adsorbent, respectively. The adsorbents showed a very high adsorption capacity due to the chemisorption of CO2. The CO2 adsorption capacity of a 70 wt.% Fe–HPA–MCF sample was 111.8 mg/g-adsorbent at 25 °C. This result indicated that the reported iron (Fe2 +) complex could be used as an efficient adsorbent for the separation of CO2. The adsorbents displayed excellent CO2 adsorption capacity and were thermally stable and recyclable.
") octahedral interconnected by the dicarboxylate groups  . This, results in a 3D metal-organic framework containing one single pore size with 1D diamond shaped channels with pores of free diameter close to 0.85 nm . However, the MIL-53 has shown reversible structural changes due to the framework interaction with guest molecules , reported as a " breathing effect " of the pores. "
[Show abstract][Hide abstract] ABSTRACT: In this work, a comparative study of various porous materials to be used as an alternative to store hydrogen by a physical adsorption process was presented. There was selected, among those commercially available, a set of the most recognized microporous materials namely: zeolites, activated carbons, carbon nanotubes and metal-organic frameworks. These samples were exhaustively characterized by nitrogen adsorption-desorption and studied in hydrogen adsorption at sub atmospheric and high pressure conditions. Discussions of the correlation between surface area and micropore volumes were performed through the adjustment of specific models, analyses on adsorbate adsorbent interaction and differences in the adsorbed volumes of hydrogen by each material. Finally were discussed the properties that should be improved in the materials to make viable the hydrogen storage by adsorption. Copyright
International Journal of Hydrogen Energy 10/2012; 37(19):14870-14880. DOI:10.1016/j.ijhydene.2012.01.166 · 3.31 Impact Factor
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