Helical Water Chain Mediated Proton Conductivity in Homochiral Metal鈥揙rganic Frameworks with Unprecedented Zeolitic unh-Topology
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- 作者：Subash Chandra Sahoo ; Tanay Kundu ; Rahul Banerjee
- 刊名：Journal of the American Chemical Society
- 出版年：2011
- 出版时间：November 9, 2011
- 年：2011
- 卷：133
- 期：44
- 页码：17950-17958
- 全文大小：1067K
- 年卷期：v.133,no.44(November 9, 2011)
- ISSN：1520-5126
文摘
Four new homochiral metal鈥搊rganic framework (MOF) isomers, [Zn(l-LCl)(Cl)](H2O)2 (1), [Zn(l-LBr)(Br)](H2O)2 (2), [Zn(d-LCl)(Cl)](H2O)2 (3), and [Zn(d-LBr)(Br)](H2O)2 (4) [L = 3-methyl-2-(pyridin-4-ylmethylamino)butanoic acid], have been synthesized by using a derivative of l-/d-valine and Zn(CH3COO)2路2H2O. A three-periodic lattice with a parallel 1D helical channel was formed along the crystallographic c-axis. Molecular rearrangement results in an unprecedented zeolitic unh-topology in 1鈥?b>4. In each case, two lattice water molecules (one H-bonded to halogen atoms) form a secondary helical continuous water chain inside the molecular helix. MOFs 1 and 2 shows different water adsorption properties and hence different water affinity. The arrangement of water molecules inside the channel was monitored by variable-temperature single-crystal X-ray diffraction, which indicated that MOF 1 has a higher water holding capacity than MOF 2. In MOF 1, water escapes at 80 掳C, while in 2 the same happens at a much lower temperature (40 掳C). All the MOFs reported here shows reversible crystallization by readily reabsorbing moisture. In MOFs 1 and 2, the frameworks are stable after solvent removal, which is confirmed by a single-crystal to single-crystal transformation. MOFs 1 and 3 show high proton conductivity of 4.45 脳 10鈥? and 4.42 脳 10鈥? S cm鈥?, respectively, while 2 and 4 shows zero proton conductivity. The above result is attributed to the fact that MOF 1 has a higher water holding capacity than MOF 2.