Frustrated Lewis pairs on pentacoordinated Al3+-enriched Al2O3 promote heterolytic hydrogen activation and hydrogenation

Abstract

As an emerging class of metal-free catalysts, frustrated Lewis pairs (FLPs) catalysts have been greatly constructed and applied in many fields. Homogeneous FLPs have witnessed significant development, while limited heterogeneous FLPs catalysts are available. Herein, we report that heterogeneous FLPs on pentacoordinated Al³⁺-enriched Al₂O₃ readily promote the heterolytic activation of H₂ and thus hydrogenation catalysis. The defect-rich Al₂O₃ was prepared by simple calcination of a carboxylate-containing Al precursor. Combinatorial studies confirmed the presence of rich FLPs on the surface of the defective Al₂O₃. In contrast to conventional alumina (γ-Al₂O₃), the FLP-containing Al₂O₃ can activate H₂ in the absence of any transition metal species. More importantly, H₂ was activated by surface FLPs in a heterolytic pathway, leading to the hydrogenation of styrene in a stepwise process. This work paves the way for the exploration of more underlying heterogeneous FLPs catalysts and further understanding of accurate active sites and catalytic mechanisms of heterogeneous FLPs at the molecular level.