Hybrid catalysts based on N-heterocyclic carbene anchored on hierarchical zeolites

With the aim of preparing Class II hybrid, based on strong chemical bonds between the organic and inorganic building units, hierarchical inorganic zeotypes, which retain the bulky microporous structure but possess an additional mesoporous network improving mass transport to internal active sites, represent a viable alternative to microporous and mesoporous materials to host organic functionalities, rendering a new and promising class of organic-inorganic hybrid catalysts to perform cascade and tandem reactions. The high mechanical and thermal stability of hierarchical materials, as well as their resistance to structural changes in the presence of organic reactants and solvents, ensure flexibility in the grafting methodologies and in a wide range of applications. Moreover, the possibility of tuning their textural hydrophobic/hydrophilic and acidic properties, together with the speciation of the active sites, allow to maximise conversion and selectivity towards the desired products. In light of the foregoing, the Ph.D. research activity was initially focused on the optimization of different synthetic strategies to prepare hierarchical zeotype catalysts. Subsequently, optimised hierarchical materials were selected and used as inorganic support to covalently anchor different organic functionalities. The as-obtained hierarchical porous organic-inorganic hybrid catalysts were deeply characterized, using a multi technique approach and their catalytic activity was evaluated in industrially-relevant reactions. Alongside, in order to get a deeper insight in the nature of organic-inorganic interface in hybrid materials, the influence of silicodactyly (i.e. number of hydrolysable alkoxy groups used by the organosilane to grab the inorganic surface) and silicopodality (i.e. number of alkyl chains through which the organosilane is anchored to the surface) in the design of a Class II hybrid catalyst was investigated through a combined experimental and computational approach.