TY - JOUR A1 - Frunza, S. A1 - Schönhals, Andreas A1 - Frunza, L. A1 - Ganea, P. A1 - Kosslick, H. A1 - Harloff, J. A1 - Schulz, A. T1 - Molecular relaxation processes in a MOF-5 structure revealed by broadband dielectric spectroscopy: signature of phenylene ring fluctuations N2 - The molecular mobility of a MOF-5 metal–organic framework was investigated by broadband dielectric spectroscopy. Three relaxation processes were revealed. The temperature dependence of their relaxation rates follows an Arrhenius law. The process observed at lower temperatures is attributed to bending fluctuations of the edges of the cages involving the Zn–O clusters. The processes ('region II') at higher temperatures were assigned to fluctuations of phenyl rings in agreement with the NMR data found by Gould et al. (J. Am. Chem. Soc. 2008, 130, 3246). The carboxylate groups might also be involved. The rotational fluctuations of the phenyl rings leading to the low frequency part of relaxation region II might be hindered either by some solvent molecules entrapped in the cages or by an interpenetrated structure and have a broad distribution of activation energies. The high frequency part of region II corresponds nearly to a Debye-like process: This is explained by a well-defined structure of empty pores. PY - 2010 U6 - https://doi.org/10.1021/jp1071617 SN - 1520-6106 SN - 1520-5207 SN - 1089-5647 VL - 114 IS - 40 SP - 12840 EP - 12846 PB - Soc. CY - Washington, DC AN - OPUS4-22255 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kosslick, H. A1 - Pitsch, I. A1 - Deutsch, J. A1 - Pohl, M.-M. A1 - Schulz, A. A1 - Vu, A.T. A1 - Nguyen, D.T. A1 - Frunza, L. A1 - Jäger, Christian T1 - Improved large mesoporous ordered molecular sieves - Stabilization and acid/base functionalization N2 - The preparation of nanoporous materials with enhanced stability using an improved synthesis route using reactive inorganic silica and alumina species is reported. This way improved mesoporous molecular sieves were obtained. The synthesized aluminum substituted mesoporous molecular materials (Al-MMS) contain very large pores of 50–200 Å size combined with an improved pore wall thickness. Increased wall thickness and Al substitution lead to an improved chemical stability against alkaline solution. The textural, structural and acid properties are investigated by physico-chemical methods. The catalytic performance acidic materials was tested in the benzoylation reaction; amino functionalized materials were studied in the base catalyzed Michael addition. KW - Nanoporous molecular sieve KW - Al substitution KW - Stability KW - Synthesis KW - Acidity KW - Catalysis PY - 2010 U6 - https://doi.org/10.1016/j.cattod.2010.03.005 SN - 0920-5861 VL - 152 IS - 1-4 SP - 54 EP - 60 PB - Elsevier CY - Amsterdam AN - OPUS4-23960 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -