Effect of Pillar Modules and Their Stoichiometry in 3D Porous Frameworks of Zn(II) with [Fe(CN)6]3鈥?/sup>: High CO2/N2 and CO2/CH4 Selectivi
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- 作者：Arpan Hazra ; Satyanarayana Bonakala ; Sandeep K. Reddy ; Sundaram Balasubramanian ; Tapas Kumar Maji
- 刊名：Inorganic Chemistry
- 出版年：2013
- 出版时间：October 7, 2013
- 年：2013
- 卷：52
- 期：19
- 页码：11385-11397
- 全文大小：923K
- 年卷期：v.52,no.19(October 7, 2013)
- ISSN：1520-510X
文摘
We report the synthesis, single-crystal structural characterization, and selective gas adsorption properties of three new 3D metal鈥搊rganic frameworks of Zn(II), {[Zn3(bipy)3(H2O)2][Fe(CN)6]2路2(bipy)路3H2O}n (1), {[Zn3(bipy)][Fe(CN)6]2路(C2H5OH)路H2O}n (2), and {[Zn3(azpy)2(H2O)2][Fe(CN)6]2路4H2O}n (3) (bipy = 4,4鈥?bipyridyl and azpy = 4,4鈥?azobipyridyl), bridged by [Fe(CN)6]3鈥?/sup> and exobidentate pyridyl-based linkers. Compounds 1鈥?b>3 have been successfully isolated by varying the organic linkers (bipy and azpy) and their ratios during the synthesis at RT. Frameworks 1 and 3 feature a biporous-type network. At 195 K, compounds 1鈥?b>3 selectively adsorb CO2 and completely exclude other small molecules, such as N2, Ar, O2, and CH4. Additionally, we have also tested the CO2 uptake capacity of 1 and 3 at ambient temperatures. By using the isotherms measured at 273 and 293 K, we have calculated the isosteric heat of CO2 adsorption, which turned out to be 35.84 and 35.53 kJ mol鈥? for 1 and 3, respectively. Furthermore, a reasonably high heat of H2 adsorption (7.97 kJ mol鈥? for 1 and 7.73 kJ mol鈥? for 3) at low temperatures suggests strong interaction of H2 molecules with the unsaturated Zn(II) metal sites and as well as with the pore surface. Frameworks 1 and 3 show high selectivity to CO2 over N2 and CH4 at 273 K, as calculated based on the IAST model. The high values of 螖HCO2 and 螖HH2 stem from the preferential electrostatic interaction of CO2 with the unsaturated metal sites, pendent nitrogen atoms of [Fe(CN)6]3鈥?/sup>, and 蟺-electron cloud of bipyridine aromatic rings as understood from first-principles density functional theory based calculations.