Pinpointing Gold’s Location In Zeolites

By using a scanning transmission electron microscopy (STEM) method, researchers have pinpointed the locations of individual catalytically active gold atoms in a zeolite support material (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201107391). Numerous studies in the past decade reporting nanosized gold clusters’ facility for catalyzing oxidations, hydrogenations, and other types of reactions have shattered the precious metal’s long-standing reputation as inert. Few of those studies, however, identified the catalytically active species and the atomic-scale interactions between gold and its support—information that could lead to improved catalysts. Jing Lu, Bruce C. Gates, and coworkers at the University of California, Davis, treated zeolite NaY, a porous crystalline solid, with Au(CH₃)₂L, where L is acetylacetonate and examined the product before and after using it to catalyze CO oxidation. On the basis of STEM and spectroscopic analysis, the team found that the ligands rapidly detach from gold upon exposure to CO and O₂, forming complexes containing a single gold atom that is bonded to approximately one zeolite oxygen atom. The reaction correlates with a change in gold from Au(III) to Au(I) and the relocation of gold atoms within the zeolite lattice.