Synthesis of platinum single-site centers through metal-ligand self-assembly on powdered metal oxide supports

Developing single-site metal catalysts has been regarded as a promising strategy to improve activity and selectivity in heterogeneous catalysis. Here, we report a metal-ligand self-assembly method to create Pt single-site centers on powdered oxide supports. Impregnating Pt and a ligand 3,6-di-2-pyridyl-1,2,4,5-tetrazine (DPTZ) simultaneously (one-step) creates Pt-DPTZ single-sites on powdered MgO, Al2O3, and CeO2. MgO has the most uniform single-sites due to a strong, non-competitive support-ligand interaction, and a support-metal interaction of appropriate strength. Pt(II) centers are stabilized between the N binding pockets of DPTZ, with minimal metallic nanoparticle formation. This system was characterized by XAS, XPS, TEM, XRD, and CO adsorption. Sequential impregnation of Pt and DPTZ (two-step) was also tested on Al2O3 and CeO2, but is not as effective as the one-step method due to limited Pt accessibility and mobility. These oxide-supported Pt-DPTZ single-sites were found to be effective catalysts in hydrosilylation reactions. This work demonstrates a metal-ligand self-assembly strategy to create metal single-site centers on high surface area catalyst supports.