NEW GO- AND RGO-BASED MORALS AND CARBENE-FUNCTIONALIZED GOLD NANOPARTICLES FOR HETEROGENEOUSLY CATALYZED REDUCTIONS

This work aims to develop and study new materials for catalytic uses, with a specific focus on reducing aromatic nitrocompounds. The work focuses on two main classes of materials. The first one is MORALs, an acronym for Metal-ORganic ALloys, a class of materials composed of organic molecules embedded in metal particles. In previous studies, this class of materials has been reported to exhibit improved catalytic properties compared to the single metal or organic molecule that constitutes it. In this work, the chosen organic molecule is graphene oxide, combined with two different metals, palladium and nickel. The resulting materials can also be further modified by reducing graphene oxide to reduced graphene oxide. All materials were analyzed using various analytical techniques and evaluated for their ability to reduce nitrobenzene. This work focuses on two main classes of materials that have recently attracted growing interest in the field of heterogeneous catalysis. The first class comprises the so-called MORALs, an acronym for Metal ORganic ALloys. These hybrid systems consist of organic molecules embedded within metallic particles. Previous studies have shown that MORALs can display catalytic properties superior to those of either the pure metal or the isolated organic molecule, suggesting the emergence of synergistic effects arising from their intimate combination. Graphene oxide (GO) was selected as the organic component due to its high specific area and ability to interact strongly with metal species. GO was combined with two different metals, palladium and nickel, chosen for their well established catalytic roles in reduction reactions. The resulting MORALs were further diversified by subjecting graphene oxide to chemical reduction, yielding reduced graphene oxide (RGO) and enabling a direct comparison between the two different modifications. All synthesized materials were thoroughly characterized using a variety of analytical techniques aimed at elucidating their structural and chemical composition. Their catalytic performance was then evaluated in the reduction of nitrobenzene, a model reaction of both academic and industrial relevance. The second class of materials investigated consists of N heterocyclic carbene (NHC)-functionalized gold nanoparticles. Gold nanoparticles (AuNPs) are widely recognized for their unique optical, electronic, and catalytic properties, which have enabled applications ranging from sensing and biomedicine to fine chemical synthesis. However, the performance and stability of AuNPs are strongly influenced by the nature of the ligands that cap their surface. In recent years, NHCs have emerged as a powerful alternative to traditional thiol based ligands, offering stronger metal-ligand bonds, enhanced robustness under reaction conditions, and the possibility of fine tuning the electronic environment of the metal surface. Two iso TT derivative were selected as the NHC precursors. This choice was motivated by the opportunity to explore the applicability of a novel ligand scaffold and to assess how its structural features influence the stabilization and reactivity of gold nanoparticles. The synthesis of the NHC functionalized AuNPs was followed by a comprehensive characterization aimed at elucidating the properties of both the organic ligand and the resulting hybrid nanomaterials. Particular attention was dedicated to understanding the interaction between the NHC and the gold surface. To evaluate their practical relevance, the supported gold nanoparticles were tested in the reduction of nitrobenzene. This reaction served as a benchmark to assess the robustness, activity, and potential advantages of the different functionalized materials. Functionalization with N heterocyclic carbenes has also been explored as a strategy to modify catalytic materials for the study of the hydrogen spillover phenomenon, a process in which activated hydrogen atoms migrate from a metal surface onto an adjacent support. Understanding and controlling spillover is of considerable interest, as it can influence reaction pathways, extend the effective catalytic surface, and enhance the performance of supported metal catalysts in hydrogenation reactions. In collaboration with Professor Bert Chandler and his research group, NHC ligands were employed to functionalize Au/rutile catalysts. This system provides an ideal platform for investigating spillover, as gold nanoparticles can activate hydrogen under specific conditions, while rutile offers well defined surface sites capable of participating in hydrogen migration. By introducing NHCs , the study aimed to probe how ligand functionalization affects the hydrogen activation step. A comprehensive set of measurements was carried out using in situ FT IR spectroscopy, enabling real time monitoring of surface species. Kinetic analyses, including Arrhenius plots and reaction order determination, were performed to highlight differences between the unfunctionalized and NHC functionalized catalysts. These experiments provided insight into how the presence of the organic ligand modifies the mechanism of hydrogen transfer across the metal–oxide interface. Finally, the materials were evaluated in the reduction of p nitrophenol. Comparing the catalytic behavior of the functionalized and unfunctionalized systems allowed for a deeper understanding of the role of NHCs in modulating hydrogen mobility and reactivity.