H5PMo10V2O40 immobilized on functionalized chloromethylated polystyrene by electrostatic interactions: a highly efficient and recyclable heterogeneous catalyst for hydroxylation of benzene

Abstract

H₅PMo₁₀V₂O₄₀ (PMoV₂) was immobilized on N,N-dimethylhexadecylamine functionalized chloromethylated polystyrene (DMA16-CMPS) by electrostatic interaction and used as a catalyst for the direct hydroxylation of benzene to phenol with H₂O₂. The results of FT-IR, XRD and TGA indicated that PMoV₂ was immobilized and finely dispersed on DMA16-CMPS, and the structure was well preserved. UV-vis DRS, EPR and XPS confirmed the presence of V⁴⁺ in the catalyst due to electronic interactions between PMoV₂ and DMA16-CMPS. The textural and morphological properties of the catalyst were characterized by N₂ adsorption–desorption, SEM and TEM. The hydrophobicity of the catalyst was also characterized by contact angle measurement. PMoV₂/DMA16-CMPS exhibited excellent catalytic performance with 22.1% conversion of benzene and a phenol yield of 21.9% at 65 °C. The high catalytic performance of PMoV₂/DMA16-CMPS is attributed to high dispersion of PMoV₂ on mesoporous and macroporous DMA16-CMPS, good benzene adsorption and phenol desorption ability, and V⁵⁺/V⁴⁺ redox pairs in the catalyst. Meanwhile, PMoV₂/DMA16-CMPS has the advantages of facile recovery and recycling.