Metal-Organic Frameworks (MOF) for gas sensing

MOFs represent a new class of soft porous materials. The permanent porosity after solvent removal allows the reversible adsorption of guest molecules for sensing. The adsorption of gases can be tuned via the interaction with the open metal sites or with polar, basic or acid groups of the linkers. The selective adsorption of a guest alters the vibrational modes of the MOF as host in the IR region in a characteristic way since MOFs as “soft” materials show extended and easy to modify lattice vibrations. In this project, MOFs are used for detecting gases by IR spectroscopy. At the beginning, the interesting MOF structures are screened, the response of the MOFs upon gas adsorption will be detected by recording the IR spectra of the MOFs as powder by DRIFT. The change of the vibrational patterns upon gas adsorption will be also by Raman spectroscopy. Finally, selected MOFs will be prepared as layer on a fiber-optics using Evanescent Wave Spectroscopy. We are one of the internationally leading groups to crystallize these MOFs as thin layers on solid surfaces like on glass fiber-optics [1]. We have developed know how to hydrophobize MOFs thus making their structure stable against humid attack and to exclude water as disturbing component in sensing [2]. We have also long-year experience in IR of gases at solid surfaces [3] and on Raman spectroscopy [4].

[1] A. Huang … J. Caro, Organosilica-functionalized zeolitic imidazolate framework ZIF-90 membrane with high gas-separation performance, Angew. Chem. Int. Ed. 51 (2012) 10551.
[2] X. Liu … J. Caro, Improvement of hydrothermal stability of zeolitic imidazolate frameworks, Chem. Commun. 49 (2013) 9140-9142.
[3] J. Heidberg, N. Guschanskaja et al., High-resolution FT-IR spectroscopy of H2 and D2 adsorbed on NaCl, Mikrochim. Acta 14 (1997) 643-645.
[4] T. F. Wietler et al., Surfactant-mediated epitaxy of silicon germanium films on silicon (001) substrates, Thin Solid Films 557 (2014) 27.