Understanding the preferential adsorption of CO2 over N 2 in a flexible metal-organic framework

Nour Nijem, Peter Thissen, Yanpeng Yao, Roberto C. Longo, Katy Roodenko, Haohan Wu, Yonggang Zhao, Kyeongjae Cho, Jing Li, David C. Langreth, Yves J. Chabal

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Abstract

The unusual uptake behavior and preferential adsorption of CO2 over N2 are investigated in a flexible metal-organic framework system, Zn2(bdc)2(bpee), where bpdc = 4,4′-biphenyl dicarboxylate and bpee = 1,2-bis(4-pyridyl)ethylene, using Raman and IR spectroscopy. The results indicate that the interaction of CO2 with the framework induces a twisting of one of its ligands, which is possible because of the type of connectivity of the carboxylate end group of the ligand to the metal center and the specific interaction of CO2 with the framework. The flexibility of the bpee pillars allows the structure to respond to the twisting, fostering the adsorption of more CO2. DFT calculations support the qualitative picture derived from the experimental analysis. The adsorption sites at higher loading have been identified using a modified van der Waals- Density Functional Theory method, showing that the more energetically favorable positions for the CO2 molecules are closer to the C=C bond of the bpee and the C-C bond of the bpdc ligands instead of the benzene and pyridine rings of these ligands. These findings are consistent with changes observed using Raman spectroscopy, which is useful for detecting both specific guest-host interactions and structural changes in the framework.

Original languageEnglish
Pages (from-to)12849-12857
Number of pages9
JournalJournal of the American Chemical Society
Volume133
Issue number32
DOIs
Publication statusPublished - Aug 17 2011

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ASJC Scopus subject areas

  • Chemistry(all)
  • Catalysis
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Nijem, N., Thissen, P., Yao, Y., Longo, R. C., Roodenko, K., Wu, H., ... Chabal, Y. J. (2011). Understanding the preferential adsorption of CO2 over N 2 in a flexible metal-organic framework. Journal of the American Chemical Society, 133(32), 12849-12857. https://doi.org/10.1021/ja2051149