title: (113)Cd Nuclear Magnetic Resonance as a Probe of Structural Dynamics in a Flexible Porous Framework Showing Selective O2/N2 and CO2/N2 Adsorption.
abstract: Two new isomorphous three-dimensional porous coordination polymers, {[Cd(bpe)0.5(bdc)(H2O)]·EtOH}n (1) and {[Cd(bpe)0.5(bdc)(H2O)]·2H2O}n (2) [bpe = 1,2-bis(4-pyridyl)ethane, and H2bdc = 1,4-benzenedicarboxylic acid], have been synthesized by altering the solvent media. Both structures contain one-dimensional channels filled with metal-bound water and guest solvent molecules, and desolvated frameworks show significant changes in structure. However, exposure to the solvent vapors (water and methanol) reverts the structure back to the as-synthesized structure, and thus, the reversible flexible nature of the structure was elucidated. The flexibility and permanent porosity were further reinforced from the CO2 adsorption profiles (195 and 273 K) that show stepwise uptake. Moreover, a high selectivity for O2 over N2 at 77 K was realized. The framework exhibits interesting solvent vapor adsorption behavior with dynamic structural transformation depending upon the size, polarity, and coordination ability of the solvent molecules. Further investigation was conducted by solid state (113)Cd nuclear magnetic resonance (NMR) spectroscopy that unambiguously advocates the reversible transformation "pentagonal-bipyramidal CdO6N → octahedral CdO5N" geometry in the desolvated state. For the first time, (113)Cd NMR has been used as a probe of structural flexibility in a porous coordination polymer system.
authors.affiliation: New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur, Bangalore 560 064, India.
authors.forename: Ritesh
authors.initials: R
authors.lastname: Haldar
authors.affiliation: Institute for Integrated Cell-Materials Sciences (iCeMS), Kyoto University , 69 Konoe-cho, Yoshida, Sokyo-ku, Kyoto, Japan.
authors.forename: Munehiro
authors.initials: M
authors.lastname: Inukai
authors.affiliation: Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University , Katsura, Nishikyo-ku, Kyoto 615 8510, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Horike
authors.affiliation: Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University , Katsura, Nishikyo-ku, Kyoto 615 8510, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Uemura
authors.affiliation: Institute for Integrated Cell-Materials Sciences (iCeMS), Kyoto University , 69 Konoe-cho, Yoshida, Sokyo-ku, Kyoto, Japan.|Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University , Katsura, Nishikyo-ku, Kyoto 615 8510, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Kitagawa
authors.affiliation: New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur, Bangalore 560 064, India.|Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur, Bangalore 560 064, India.
authors.forename: Tapas Kumar
authors.initials: TK
authors.lastname: Maji