Confinement of Highly Luminescent Lead Clusters in Zeolite A

Metal clusters confined inside zeolite frameworks display unique electronic, catalytic, and optical properties. However, so far only confined silver clusters have shown peculiar luminescent properties, displaying high photoluminescent quantum efficiencies reaching almost unity. In this study, we demonstrate the self-assembly and confinement of highly luminescent lead (Pb) clusters into the molecular-sized cavities of Linde Type A (LTA) zeolites. These Pb-LTA samples display an intense deep-blue emission with external quantum efficiencies up to69% in their partially dehydrated state. A tetrahedral lead cluster (P134) with unusually short Pb Pb distances and hydroxyl ligands was identified as responsible for the luminescence as determined by X-ray absorption fine structure (XAFS) analysis. The in-depth characterization of the Pb-zeolites, reported here, sets the stage for elucidating the structure-to-luminescent relationship of other zeolite-embedded clusters.