Strong CO{sub 2} binding in a water-stable, triazolate-bridged metal-organic framework functionalized with ethylenediamine
- University of California Berkeley, Berkeley, CA (United States). Dept. of Chemistry
Reaction of CuCl{sub 2}{center_dot}2H{sub 2}O with 1,3,5-tris(1H-1,2,3-triazol-5-yl)benzene (H{sub 3}BTTri) in DMF at 100{sup o}C generates the metal-organic framework H{sub 3}((Cu{sub 4}Cl){sub 3}(BTTri){sub 8}(DMF){sub 12}){center_dot}7DMF {center_dot} 76H{sub 2}O(1-DMF). The sodalite-type structure of the framework consists of BTTri{sup 3-}-linked (Cu{sub 4}Cl){sup 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{sup o}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 degrees C generated H{sub 3}(Cu{sub 4}Cl{sub 3}(BTTri){sub 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 N{sub 2} adsorption isotherms indicate a reduction in the BET surface area from 1770 to 345 m{sup 2}/g following grafting. The H{sub 2} adsorption data at 77 K for 1 indicate a fully reversible uptake of 1.2 wt % at 1.2 bar, while the CO{sub 2} isotherm at 195 K shows a maximal uptake of 90 wt % at 1 bar. Compared to 1, the alkylamine-functionalized framework I-en exhibits a higher uptake of CO{sub 2} at 298 K and pressures up to ca. 0.1 bar, as well as a higher CO{sub 2}/N{sub 2} selectivity at all measured pressures. Significantly, 1-en also exhibits an isosteric heat of CO{sub 2} 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 CO{sub 2} from low-pressure flue gas streams.
- OSTI ID:
- 21212793
- Journal Information:
- Journal of the American Chemical Society, Vol. 131, Issue 25; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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