Functionalization of open-metal sites in stable MOFs through the use of small post-functionalized anchor molecules

Details

Supervisors

Hermans, Sophie ; Filinchuk, Yaroslav

Faculty

Faculté des sciences

Degree label

Master [120] en sciences chimiques

Abstract

This project aims at synthesizing stable Ti, Al and Zr-based metal-organic frameworks (MOFs) with accessible open-metal sites, in order to functionalize them with ethylenediamine-like molecules, to obtain composite porous materials with –NH2 functionalities. These materials are of interest in gas storage and catalysis. After a general introduction, the present project is divided into four experimental parts. The first three cover the synthesis of stable MIL-100 and MIL-101 MOFs based on Al and/or Ti centres, as well as of UiO-66 Zr. The last part deals with the synthesis of a fluorescent probe that allows the detection of free amine groups. In the first part, our attempts to synthesize MIL-100 MOFs structures based on Al and/or Ti as metal centres are described. The synthesis of pure MIL-100-Al was performed at a large scale, and the impact of the reagent concentrations, reaction time and temperature were evaluated. To produce MIL-100-TiIV, the [Ti6O6(4-tbbz)6(OiPr)6] cluster and Ti(OiPr)4 compound were used as metal precursors. Solvothermal and mechanochemical methods were explored, as well as milder reaction conditions. However, none of those approaches allowed producing the target MIL 100 TiIV. Syntheses with a commercial mixed-metal TiIII/Al source were also tried at different temperatures, with different reaction times, washing methods and concentrations of HCl as modulator. In this case, the syntheses only led to compounds with very poor crystallinity. The oxidation of the products by air was also evaluated and the structure seemed to withstand this treatment. The second part deals with different attempts to synthesize MIL 101 structures. MIL 101 TiIII was successfully produced from TiCl3 by a procedure from the literature, but with a smaller surface area. However, we observed a complete collapse of the MOF’s structure upon contact with air. Due to the small amounts of available TiCl3, attempts were made to obtain mixed MIL 100 (Al)TiIII from (TiCl3)3∙AlCl3 instead. Unfortunately, those attempts only yielded amorphous samples. The third part relates to the synthesis of UiO-66-Zr. This MOF was obtained at gram scale with high crystallinity. However, its functionalization could not be explored due to the Covid-19 lockdown. The last part describes the synthesis of a BODIPY derivative. This fluorescent probe for the detection of –NH2 functions was obtained in small amounts with satisfying purity and a qualitative test under UV irradiation confirmed its ability to detect free amines sites. Conclusions and perspectives end up this thesis, putting forward the functionalization of MOFs with ethylenediamine and the capture of acidic gases such as CO2 as the most interesting direction, as well as synthesis of mixed metal MIL 100 (Al)Ti.