The present thesis is focused on the design of hybrid magnetic materials comprising of magnetic nanoparticles and an organocatalyst for applications in several catalytic transformations. One such system, composed of iron oxide magnetic nanoparticles and a polysaccharide, k-carrageenan, is used for the Michael addition of aldehydes to nitroalkenes, proving to be very efficient for this reaction. Other catalytic systems reported herein consist of magnetic nanoparticles and an A₃B type porphyrin. These hybrid materials were tested for the Knoevenagel condensation of aldehydes at room temperature, providing the desired adducts in high yields. Even more, one of these systems was also studied as optical sensor for CO₂ detection proving to be highly efficient as well. Hybrid materials containing iron oxide magnetic nanoparticles and an amino polysaccharide, chitosan, have also been designed and studied in catalysis. These materials were tested in the aldol condensation of p-nitrobenzaldehyde with cyclohexanone, at room temperature, leading to the desired products in good yields and high enantioselectivities. Moreover, a new dual catalytic system was also designed. This system comprises of gold iron oxide dumbbells functionalized with chitosan. The main objective is to combine metal and organocatalysis on the same solid support. In this case, gold would act as the metal catalyst, whilst chitosan would be responsible for the organocatalytic transformation.