Strong CO2 Binding in a Water-Stable, Triazolate-Bridged Metal−Organic Framework Functionalized with Ethylenediamine

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• 作者：Aude Demessence ; Deanna M. D’ ; Alessandro ; Maw Lin Foo ; Jeffrey R. Long
• 刊名：Journal of the American Chemical Society
• 出版年：2009
• 出版时间：July 1, 2009
• 年：2009
• 卷：131
• 期：25
• 页码：8784-8786
• 全文大小：212K
• 年卷期：v.131,no.25(July 1, 2009)
• ISSN：1520-5126

文摘

Reaction of CuCl₂·2H₂O with 1,3,5-tris(1H-1,2,3-triazol-5-yl)benzene (H₃BTTri) in DMF at 100 °C generates the metal−organic framework H₃[(Cu₄Cl)₃(BTTri)₈(DMF)₁₂]·7DMF·76H₂O (1-DMF). The sodalite-type structure of the framework consists of BTTri³⁻-linked [Cu₄Cl]⁷⁺ square clusters in which each Cu^II center has a terminal DMF ligand directed toward the interior of a large pore. The framework exhibits a high thermal stability of up to 270 °C, as well as exceptional chemical stability in air, boiling water, and acidic media. Following exchange of the guest solvent and bound DMF molecules for methanol to give 1-MeOH, complete desolvation of the framework at 180 °C generated H₃[(Cu₄Cl)₃(BTTri)₈] (1) with exposed Cu^II sites on its surface. Following a previously reported protocol, ethylenediamine molecules were grafted onto these sites to afford 1-en, featuring terminal alkylamine groups. The N₂ adsorption isotherms indicate a reduction in the BET surface area from 1770 to 345 m²/g following grafting. The H₂ adsorption data at 77 K for 1 indicate a fully reversible uptake of 1.2 wt % at 1.2 bar, while the CO₂ isotherm at 195 K shows a maximal uptake of 90 wt % at 1 bar. Compared to 1, the alkylamine-functionalized framework 1-en exhibits a higher uptake of CO₂ at 298 K and pressures up to ca. 0.1 bar, as well as a higher CO₂/N₂ selectivity at all measured pressures. Significantly, 1-en also exhibits an isosteric heat of CO₂ adsorption of 90 kJ/mol, which is much higher than the 21 kJ/mol observed for 1. This chemisorption interaction is the strongest reported to date for a metal−organic framework and points toward the potential utility of alkylamine-appended frameworks for the postcombustion capture of CO₂ from low-pressure flue gas streams.