Elucidating Confinement and Microenvironment of Ru Clusters Stably Confined in MFI Zeolite for Efficient Propane Oxidation

Abstract

Achieving active and stable heterogeneous catalysts by encapsulating noble metal species within zeolites is highly promising for high utilization and cost efficiency in thermal and environmental catalytic reactions. Ru considered an economical noble metal alternative with comparable performance, faces great challenges within MFI-type microporous zeolites due to its high cohesive energy and mobility. Herein, an innovative strategy was explored coupling hydrothermal in situ ligand protection with stepwise calcination in a flowing atmosphere to embed ultrasmall Ru clusters anchored at K+-healed silanol sites (≡Si–Ruδ+-O-K complexes) within 10-membered ring sinusoidal channels of MFI. Comprehensive experiments and theoretical calculations unveiled that the interplay between confined Ru clusters and MFI induces local strain in MFI, creating a unique catalytic microenvironment around the Ru clusters. This synergy exhibits superior alkane deep oxidation, performance owing to the confined Ru clusters and the MFI microenvironment collectively pre-activate C3H8 and O2, facilitate the cleavage of C-H and C-C bonds at low temperatures. Notably, the stable geometric and electronic properties of confined Ru show exceptional thermal stability up to 1000 °C, rivaling fresh catalysts. These findings shed vital methodological and mechanistic insights for developing efficacious heterogeneous catalysts for thermal catalysis.