Proline Functionalization of the Mesoporous Metal−Organic Framework DUT-32

The linker functionalization strategy was applied to incorporate proline moieties into a metal–organic framework (MOF). When 4,4′-biphenyldicarboxylic acid was replaced with a Boc-protected proline-functionalized linker (H₂<b>L</b>) in the synthesis of DUT-32 (DUT = Dresden University of Technology), a highly porous enantiomerically pure MOF (DUT-32-NHProBoc) was obtained, as could be confirmed by enantioselective high-performance liquid chromatography (HPLC) measurements and solid-state NMR experiments. Isotope labeling of the chiral side group proline enabled highly sensitive one- and two-dimensional solid-state ¹³C NMR experiments. For samples loaded with (<i>S</i>)-1-phenyl-2,2,2-trifluoroethanol [(<i>S</i>)-TFPE], the proline groups are shown to exhibit a lower mobility than that for (<i>R</i>)-TFPE-loaded samples. This indicates a preferred interaction of the shift agent (<i>S</i>)-TFPE with the chiral moieties. The high porosity of the compound is reflected by an exceptionally high ethyl cinnamate adsorption capacity. However, postsynthetic thermal deprotection of Boc−proline in the MOF leads to racemization of the chiral center, which was verified by stereoselective HPLC experiments and asymmetric catalysis of aldol addition

Structural Characterization of Micro- and Mesoporous Carbon Materials Using In Situ High Pressure ¹²⁹Xe NMR Spectroscopy

In situ high pressure ¹²⁹Xe NMR spectroscopy in combination with volumetric adsorption measurements were used for the textural characterization of different carbon materials with well-defined porosity including microporous carbide-derived carbons, ordered mesoporous carbide-derived carbon, and ordered mesoporous CMK-3. Adsorption/desorption isotherms were measured also by NMR up to relative pressures close to <i>p</i>/<i>p</i>₀ = 1 at 237 K. The ¹²⁹Xe NMR chemical shift of xenon adsorbed in porous carbons is found to be correlated with the pore size in analogy to other materials such as zeolites. In addition, these measurements were performed loading the samples with <i>n</i>-nonane. Nonane molecules preferentially block the micropores. However, ¹²⁹Xe NMR spectroscopy proves that the nonane also influences the mesopores, thus providing information about the pore system in hierarchically structured materials