Two robust polyoxovanadate clusters having a square-prism V10Ox core for efficient catalysis of benzene hydroxylation to phenol

Abstract

Hydrogen peroxide (H₂O₂)-mediated oxidation of benzene to phenol in a single step is a promising approach for green phenol production. Nevertheless, constructing robust and efficient heterogeneous catalysts with atomic precision remains a long-sought pursuit. Here we present the synthesis of two robust V₁₀ oxo clusters holding different capping ligands, named V₁₀-BTA and V₁₀-CBTA. Single crystal analysis reveals that two decavanadate clusters exhibit a distinct braced square-prism configuration with different benzotriazole ligands capped on the edges of the square-prism, and V₁₀-BTA is an example of a rare highly reduced vanadium cluster. Accordingly, functionalization of the V₁₀ square-prism with organic linkers provides enhanced structural stability and introduces porosity to the cluster assembly in terms of heterogeneous application, thus allowing more active sites to be accessible and increasing reactivity. Remarkably, V₁₀-BTA exhibits outstanding catalytic performance in the one-pot hydroxylation reaction, achieving a benzene to phenol conversion of 32.2% with a phenol selectivity of 99%, arising from the synergistic interplay between the braced square-prism configuration and the active V sites as confirmed by control experiments. Besides, V₁₀-BTA displays broad substrate compatibility and superior recyclability for six successive cycles. This study provides an imperative strategy to develop POV clusters with excellent stability, while contributing to high catalytic efficiency for some challenging chemical transformations.