Metal–organic frameworks of general composition [M6(OH)4(O)4(PDC)6−x(Cl)2x(H2O)2x] with M = Zr, Ce, Hf; PDC2− = 2,5-pyridinedicarboxylate and 0 ≤ x ≤ 2 were obtained under reflux using formic, nitric or acetic acid as an additive. Rietveld refinements carried out using a fixed occupancy of the linker molecules according to the results of thermogravimetric measurements confirmed that the MOFs crystallize in the UiO-66 type structure and demonstrate that the structural models describe the data well. Further characterization was carried out by NMR spectroscopy, thermogravimetric analysis, Zr K-edge EXAFS- and Ce L3-edge XANES measurements. To highlight the influence of the additional nitrogen atom of the pyridine ring, luminescence and vapour sorption measurements were carried out. The hydrophilisation of the MOFs was shown by the adsorption of water at lower p/p0 (<0.2) values compared to the corresponding BDC-MOFs (0.3). For water and methanol stability cycling adsorption experiments were carried out to evaluate the MOFs as potential adsorbents in heat transformation applications.

Synthesis of M-UiO-66 (M = Zr, Ce or Hf) employing 2,5-pyridinedicarboxylic acid as a linker: defect chemistry, framework hydrophilisation and sorption properties

Lomachenko, K A;Lamberti, C;
2018-01-01

Abstract

Metal–organic frameworks of general composition [M6(OH)4(O)4(PDC)6−x(Cl)2x(H2O)2x] with M = Zr, Ce, Hf; PDC2− = 2,5-pyridinedicarboxylate and 0 ≤ x ≤ 2 were obtained under reflux using formic, nitric or acetic acid as an additive. Rietveld refinements carried out using a fixed occupancy of the linker molecules according to the results of thermogravimetric measurements confirmed that the MOFs crystallize in the UiO-66 type structure and demonstrate that the structural models describe the data well. Further characterization was carried out by NMR spectroscopy, thermogravimetric analysis, Zr K-edge EXAFS- and Ce L3-edge XANES measurements. To highlight the influence of the additional nitrogen atom of the pyridine ring, luminescence and vapour sorption measurements were carried out. The hydrophilisation of the MOFs was shown by the adsorption of water at lower p/p0 (<0.2) values compared to the corresponding BDC-MOFs (0.3). For water and methanol stability cycling adsorption experiments were carried out to evaluate the MOFs as potential adsorbents in heat transformation applications.
2018
47
4
1062
1070
http://pubs.rsc.org/en/Content/ArticleLanding/2018/DT/C7DT03641H#!divAbstract
Metal–organic frameworks, MOF, UiO-66, Ce-UiO-66, Hf-UiO-66,EXAFS, XRD, water adsorption, methanol adsorption
Waitschat, S; Fröhlich, D; Reinsch, H; Terraschke, H; Lomachenko, K A; Lamberti, C; Kummer, H; Helling, T; Baumgartner, M; Henninger, S; Stock, N
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/1665075
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