title: Proline functionalization of the mesoporous metal-organic framework DUT-32.
abstract: 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 (H(2)L) 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 (13)C NMR experiments. For samples loaded with (S)-1-phenyl-2,2,2-trifluoroethanol [(S)-TFPE], the proline groups are shown to exhibit a lower mobility than that for (R)-TFPE-loaded samples. This indicates a preferred interaction of the shift agent (S)-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.
authors.affiliation: Department of Inorganic Chemistry and ‡Department of Bioanalytical Chemistry, Technische Universität Dresden , Bergstraße 66, D-01069 Dresden, Germany.
authors.forename: Christel
authors.initials: C
authors.lastname: Kutzscher
authors.forename: Herbert C
authors.initials: HC
authors.lastname: Hoffmann
authors.forename: Simon
authors.initials: S
authors.lastname: Krause
authors.forename: Ulrich
authors.initials: U
authors.lastname: Stoeck
authors.forename: Irena
authors.initials: I
authors.lastname: Senkovska
authors.forename: Eike
authors.initials: E
authors.lastname: Brunner
authors.forename: Stefan
authors.initials: S
authors.lastname: Kaskel
mesh_terms: D000327:Adsorption; D001713:Biphenyl Compounds / Q000737:chemistry; D002384:Catalysis; D060326:Chemistry Techniques, Synthetic; D002851:Chromatography, High Pressure Liquid; D002934:Cinnamates / Q000737:chemistry; D003998:Dicarboxylic Acids / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D016062:Porosity; D011392:Proline / Q000737:chemistry*; D013237:Stereoisomerism; D014270:Trifluoroethanol / Q000031:analogs & derivatives / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: C528617:1-phenyl-2,2,2-trifluoroethanol; C535263:4,4'-biphenyldicarboxylic acid; D001713:Biphenyl Compounds; D002934:Cinnamates; D003998:Dicarboxylic Acids; D009942:Organometallic Compounds; D014270:Trifluoroethanol; D011392:Proline; C451418:ethyl cinnamate