Dai, Jun. Mechanisms of adsorption of aromatic nitrogen compounds and aromatic hydrocarbons on metal-organic frameworks (Mofs). Retrieved from https://doi.org/doi:10.7282/T3QF8R98
DescriptionMetal-Organic Frameworks (MOFs) constitute a class of novel porous materials that have attracted significant interest due to their applications in separation, storage, catalysis and chemical sensing. Their large surface area and highly porous structure make these materials excellent absorbents with a huge uptake capacity for many adsorbates of interest. Using complementary spectroscopic methods, we studied the mechanisms of adsorption of representative fused-ring aromatic compounds, namely indole and naphthalene, on the following MOFs: Basolite F300, MIL-100(Fe) and Basolite A100. Fluorescence spectroscopy and near-UV/Visible diffuse reflectance spectroscopy (near-UV-Vis DRS) studies demonstrate that naphthalene is confined within the mesocavity of F300 MOF. Moreover, we detected coordination bonds between adsorbed indole and F300 when indole was weakly electronically bound to Fe (III) CUS in F300 and MIL-100(Fe). Direct spectroscopic proof of the formation of an adsorption complex of indole with F300 and MIL-100(Fe) MOFs was obtained by near-UV-Vis DRS, wavelength-dependent fluorescence spectroscopy, and complementary time-dependent fluorescence spectroscopy. We have also determined the origin of the UV-Vis fluorescence in A100 MOF. We show that this fluorescence comes from the 1,4-benzenedicarboxylic acid (BDC) linker. The A100 MOF forms stoichiometric adsorption complexes with both indole and naphthalene. In these adsorption complexes, quenching of the ligand-based fluorescence from the BDC linker by the indole adsorbate was found. Based on wavelength-dependent fluorescence spectroscopy, we propose the adsorption of indole and naphthalene onto A100 MOF occurs via π-π interactions with the BDC linker.