Haldar Ritesh, Inukai Munehiro, Horike Satoshi, Uemura Kazuhiro, Kitagawa Susumu, Maji Tapas Kumar
New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur, Bangalore 560 064, India.
Institute for Integrated Cell-Materials Sciences (iCeMS), Kyoto University , 69 Konoe-cho, Yoshida, Sokyo-ku, Kyoto, Japan.
Inorg Chem. 2016 May 2;55(9):4166-72. doi: 10.1021/acs.inorgchem.5b02873. Epub 2016 Apr 13.
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.
通过改变溶剂介质合成了两种新的同构三维多孔配位聚合物，{[Cd(bpe)0.5(bdc)(H2O)]·EtOH}n（1）和{[Cd(bpe)0.5(bdc)(H2O)]·2H2O}n（2）[bpe = 1,2-双（4-吡啶基）乙烷，H2bdc = 1,4-苯二甲酸]。两种结构都包含一维通道，通道中填充有与金属结合的水分子和客体溶剂分子，脱溶剂后的骨架结构显示出显著变化。然而，暴露于溶剂蒸汽（水和甲醇）中会使结构恢复到合成时的结构，因此，阐明了该结构的可逆柔性本质。通过在195和273 K下的CO2吸附曲线进一步增强了其柔性和永久孔隙率，该曲线显示出逐步吸附。此外，在77 K下实现了对O2相对于N2的高选择性。该骨架表现出有趣的溶剂蒸汽吸附行为，其动态结构转变取决于溶剂分子的大小、极性和配位能力。通过固态（113）Cd核磁共振（NMR）光谱进行了进一步研究，该研究明确支持了脱溶剂状态下“五角双锥CdO6N→八面体CdO5N”几何结构的可逆转变。首次将（113）Cd NMR用作多孔配位聚合物体系中结构柔性的探针。
