Préparation et caractérisation des nanomatériaux, application en synthèse organique

Abstract

In recent years, the remarkable catalytic properties of gold, a precious metal, have attracted considerable interest. The dispersion of the gold, as well as the structure and interaction between the gold nanoparticles and the supports, and the type of support used, are well-established factors that influence the catalytic and adsorption properties. One of the main challenges facing supported gold catalysts is the agglomeration of the gold particles, which leads to deactivation of the catalyst. The porosity of the support material plays a crucial role in controlling the agglomeration of the metal particles. Mesoporous materials, in particular SBA-15 mesoporous silicas, are receiving particular attention due to their high specific surface area, large pore size, thick silica walls for thermal and hydrothermal stability and high surface hydroxyl density, as well as their exceptional performance as highly efficient catalysts. However, the use of mesoporous silicas as acid supports poses a problem for gold deposition. The negatively charged surface of the silica hinders the adsorption of gold precursor anions. It therefore becomes imperative to modify the surface properties of mesoporous silicas by incorporating functional groups on the channel walls.Generally, functional organic groups containing polar moieties are introduced into mesoporous silicas to stabilise nanoparticles and inhibit their aggregation. In addition, the creation of solid heterogeneous catalysts containing organic functionalities is considered to be a convincing solution. In this context, the first part of this thesis was devoted to the design of a heterogeneous catalyst based on gold nanoparticles dispersed on amine-modified SBA-15 mesoporous silica (Au/SBA-15-NH2).The catalyst was characterised by various

techniques: powder XRD, N2 adsorption/desorption, FT-IR spectroscopy. The results show that the SBA- 15 silica has a stable, ordered structure even after organo-functionalisation with aminopropylsilane, and

that the gold nanoparticles are located in the pores of the SBA-15 with average sizes of 1-8 nm. In the second part, the reactivity of the catalyst was examined in a four-component coupling process for the synthesis of β-acetamido ketones, which are versatile mediators in that their skeletons exist in a number of pharmaceutical and biological substances. Thus, the chosen methodology offers many advantages, including high yields, a simple procedure and fast reaction times. The approach of the third part is to evaluate the effectiveness of the mesoporous silica support SBA-15 functionalized with organic binders containing amines, to inhibit copper corrosion in various acidic environments. The results show that the support is an excellent inhibitor for protecting copper against corrosion, particularly in a 0.5M sulphuric acid environment. Finally, the biological activity of the materials synthesised was studied.