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Metal-Organic Frameworks (MOFs) are porous coordination networks assembled through metal complexes with organic linkers. Due to their chemical versatility, these materials are being investigated for various applications including gas storage and separation, biomedicine and catalysis. The aim of this work is the encapsulation of the model β-alanine amino-acid in the nanostructured zirconium-based MOF (UiO-66). Additionally, ligand functionalization and defect engineering have been carried out to produce UiO-66 derivatives, in order to modify the host-guest interactions, and hence study their influence on the β-alanine loading capacity and release kinetics. The as-obtained materials have been characterized by X-ray diffraction (XRD), X-ray thermo diffraction (TDX), infrared (IR) spectroscopy, thermogravimetric analysis-differential scanning calorimetry (TG-DSC) and elemental analysis (EA). Morphology of nanoscale MOFs has been explored by transition electron microscopy (TEM). Adsorption isotherms have been constructed, and the concentration of β-alanine in the post-adsorption solution (supernatant) has been quantified by high performance liquid chromatography coupled with mass spectroscopy (HPLC-MS). The β-alanine loading degree of the solids has been quantified by Elemental analyses. Adsorption capacity values indicate that the presence of hydroxyl groups at the organic linkers of the materials enhance the host-guess affinity between the framework and the adsorbate. The influence of defect engineering on alanine adsorption is not so obvious, since despite the adsorption isotherms suggest that defect degree can favours or hinder the process, the experimental accuracy of the adsorption isotherms at high concentrations, summed to the alanine loading degrees obtained from elemental analysis made the analyses not conclusive. Desorption experiments, developed for hydroxylates derivatives indicates that independently on adsorption capacity values, the compounds behave similar during the β-alanine release. β -alanine adsorbing mechanism based on a combination of host-guest interaction at low concentrations, and covalent anchoring/ligand displacement by β-alanine at the inorganic clusters has been proposed |
