Platinum clusters confined in FAU–LTA hierarchical porous composite with a core–shell structure

Hierarchical porous composite with a core–shell structure possessing FAU-type zeolite core (zeolite X) and LTA-type zeolite shell (zeolite A) has been prepared. The intimate growth of zeolite shell is achieved by in situ crystallization of the LTA zeolite crystals with size of 1 μm on large single FAU-type crystals with size of about 60–90 μm. Direct visualization of the core–shell material is provided by X-ray microbeam measurements using synchrotron radiation on a single crystal complemented with field emission scanning electron microscopic study. The nitrogen sorption data confirmed that the access to large single FAU-type core is controlled by the defect-free LTA-type shell. Sorption measurements showed that about 98% of core crystals are covered by the LTA shells. Further the FAU–LTA core–shell material is used as a host for the stabilization of platinum clusters. The Pt location, mean size and distribution have been studied by CO chemisorption followed by FT-IR spectroscopy. High loading of platinum accessible to CO molecules in the core–shell material is achieved. The use of the FAU–LTA matrix allowed the stabilization of two different sizes of Pt clusters. Additional advantage of the core–shell material is the protection of the clusters from thermal sintering and poisoning, which is of significant importance for future catalysts.