A versatile desilication design strategy for the creation of hierarchical H-ZSM-5 catalysts with different Si/Al ratio has been demonstrated. The nature, strength and the accessibility of the acid sites after the alkaline treatment was elucidated by employing a range of physico-chemical characterization tools; notably probebased FTIR spectroscopy along with SS MAS-NMR. In addition, structural and textural properties of the hierarchical zeolites were also explored and compared to their corresponding microporous analogues. CO was used to probe the acidic properties of the hierarchical zeolites with the concomitant deployment of a bulky molecular probe, 2,4,6-trimethylpyridine (collidine), which is too large to access the micropores, to specifically investigate the enhanced accessibility of the active sites. The hierarchical zeolites were evaluated in the industrially relevant, acid-catalyzed Beckmann rearrangement of cyclohexanone oxime to -caprolactam, the precursor for Nylon-6, in liquid phase and at low-temperatures. The catalytic findings with the hierarchical catalysts reveal a significant enhancement in the production of -caprolactam, compared with the parent microporous H-ZSM-5 zeolite, thereby highlighting the merits of our design approach in facilitating enhanced diffusion and masstransfer.

Hybrid organic-inorganic catalysts have been extensively investigated by several research groups in the last decades, as they allow combining the structural robust-ness of inorganic solids with the versatility of organic chemistry. Within the field of hybrid catalysts, synthetic strategies based on silica are among the most exploitable, due to the convenience of sol-gel chemistry, to the array of silyl-derivative precursors that can be synthesized and to the number of post-synthetic functionalization strategies available, amongst others. This review proposes to highlight these advantages, firstly describing the most common synthetic tools and the chemistry behind sol-gel syntheses of hybrid catalysts, then presenting exemplificative studies involving mono- and multi-functional silica-based hybrid catalysts featuring different types of active sites (acid, base, redox). Materials obtained through different approaches are described and their properties, as well as their catalytic performances, are compared. The general scope of this review is to gather useful information for those approaching the synthesis of organic-inorganic hybrid materials, while providing an overview on the state-of-the art in the synthesis of such materials and highlighting their capacities.

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Hybrid heterogeneous catalysts containing (fluoro)aryl-sulfonic groups were characterized through combined spectroscopic techniques and adsorption of probe molecules, with their reactivity being modulated for acetal formation.

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The research work described in this Doctoral Thesis was developed within the frame of the MULTI2HYCAT European Project (grant agreement N. 720783) and it is focused on the synthesis and characterization of mono-and multi-functional hybrid catalysts featuring acid, base or redox active sites. Several research lines have been developed in parallel to design multiple hybrid catalysts for different catalytic processes, building upon the needs of the industrial partners. xvi 3.4. Results and discussion 3.4.1. Synthesis of the hybrid catalysts 3.4.2. Characterization 3.4.3. Adsorption of probe molecules followed by spectroscopies (FTIR and NMR) 3.4.4. Catalytic activity 3.4.5. Hydrophobic HSO3-CH3NOS-F and HSO3-CH3NOS-F hybrid materials 3.5. Conclusions 3.6. References 4. Hybrid Mesoporous Silica-Supported Base Organocatalysts for C-C Bond Formation 4.1. Amine-silanol cooperative catalysis for C-C bond formation 4.2. Scope of this work 4.3. Experimental 4.3.1. Synthesis of the materials 4.3.2. Characterization 4.3.3. Catalytic tests 4.4. Results and discussion 4.4.1. Synthesis and characterization of the hybrid base catalysts 4.4.2. Catalytic activity 4.5. Synthesis of silica-supported phosphazene materials (P1) 4.6. Conclusions 4.7. References 5. Synthesis of Multi-Functional Hybrid Catalysts for Cascade Reactions 5.1.

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