Polycrystalline zeolite aggregates, with high catalytic activity and adjustable mesoscopic pores, can be used in catalysis to provides both catalytic activity and mass-transport of the reactants. Zeolites are crystalline aluminosilicate materials that are technologically important for their applications in catalysis, radioactive ion sequestration, and purification systems. An advanced strategy for controlling the aggregation of zeolite seeds, by functionalizing their exterior surfaces with organosilane species, has led to zeolite structures with bimodal nano/mesoporosities and favorable catalytic properties. The use of organosilane moiety represents an important because the material obtained combines high catalytic activity with low resistance to mass-transport. These materials can offer new opportunities for catalytic reactions or purifications involving large molecules, once the preparation and structures are optimized.