Topological Placement of Metal Nanoparticles in MFI Zeolitic Framework With Intriguing Mesoporous Architecture

The efficient utilization of nanoporous zeolites requires careful tuning of the inherent physicochemical attributes of crystals such as porosity, diffusion pathlengths, and chemical composition. The metal loading in the zeolite imparts extra functional multiplicity owing to additional Lewis's acid centers. However, the higher catalytic performance is strongly determined by the spatial location of metal nanoparticles and their sizes. Here, modified desilication routes in the presence of Ethylene Diamine (EDA) is explored to generate mesopores and core-shell architecture for both Silicalite-1 (S-1) and ZSM-5. EDA helped in stabilizing the zeolitic core of MFI for controlled desilication. Interestingly, evidence of layered depletion of the inner core and recrystallization of the partially ordered external surface is provided. Subsequently, multiple EDA-assisted synthetic protocols are used to load metals on topologically different locations of MFI crystals (S-1 and ZSM-5). Here, explicit metal loading on the external surface and inside the core is showcased. Through the in situ method, metal can deposit on both the external surface and the inner core. The study presents a comprehensive picture using two metals (Pd and Ag), where EDA helps in ensuring uniform distribution. Overall, the complementary methodology is established for controlled porosity tuning and selective metal placement in MFI framework.