Effect of Zirconia Crystalline Phases on Pt Dispersion and Catalytic Performance in Alkyne Hydrosilylation

The crystalline phase of catalyst support plays a crucial role in governing the dispersion and activity of supported metal species. Herein, we investigate the influence of amorphous (a-), monoclinic (m-), and tetragonal ZrO2 (t-ZrO2) support on the performance of Pt/ZrO2 catalysts in the hydrosilylation of alkynes. Catalysts supported on m-ZrO2 and t-ZrO2 exhibited high Pt dispersion and catalytic activity, while those supported on a-ZrO2 showed poor performance due to encapsulation of Pt during heat treatment. When a-ZrO2 was calcined, it underwent a transformation to the monoclinic phase, which improved the dispersion and catalytic activity of the supported Pt. Structural and spectroscopic analyses including XRD, H2-TPR, Pt L3-edge EXAFS, and CO chemisorption revealed that the monoclinic and tetragonal phase uniquely stabilizes Pt at or near the surface. However, when comparing Pt/m-ZrO2 and Pt/t-ZrO2, the former showed higher dispersion and better reusability than the latter. These findings highlight the critical role of ZrO2 support crystallinity in tuning metal-support interactions and establish m-ZrO2 as promising platform for designing efficient hydrosilylation catalysts.