Probing Adsorption Interactions In Metal-Organic Frameworks Using X-ray Spectroscopy 

W. S. Drisdell, R. Poloni, T. M. McDonald, J. R. Long, B. Smit, J. B. Neaton, D. G. Prendergast, and J. B. Kortright, Probing Adsorption Interactions In Metal-Organic Frameworks Using X-ray Spectroscopy J. Am. Chem. Soc  (2013)

Abstract: We explore the local electronic signatures of molecular adsorption at coordinatively unsaturated binding sites in the metal-organic framework Mg-MOF-74 using X-ray spectroscopy and first principles calculations. In situ measurements at the Mg K-edge reveal distinct pre-edge absorption features associated with the unique, open coordination of the Mg sites which are suppressed upon adsorption of CO2 and N,N'-dimethylformamide. Density functional theory shows that these spectral changes arise from modifications of local symmetry around the Mg sites upon gas uptake and are strongly dependent on the metal-adsorbate binding strength. The expanded MOF Mg2(dobpdc) displays the same behavior upon adsorption of CO2 and N,N'-dimethylethylenediamine. Similar sensitivity to local symmetry is expected for any open metal site, making X-ray spectroscopy an ideal tool for examining adsorption in such MOFs. Qualitative agreement between ambient temperature experimental and zero K theoretical spectra is good, with minor discrepancies thought to result from framework vibrational motion.

© Berend Smit 2013