Polymer-anchored vanadium(IV)–substituted benzimidazole: an Efficient green catalyst for aqueous oxidation of organic substrates
摘要
Vanadium complexes are efficacious catalysts for the oxidation of diverse organic substrates. Immobilizing these complexes on solid supports enhances their chemical and thermal stability, improves catalytic efficiency, and facilitates easy separation from the reaction mixture, thereby minimizing contamination of the final product. A novel vanadium complex of substituted benzimidazole, 2(2'-quinolylbenzimodazole) immobilized on a partially chloromethylated polystyrene cross linked with divinyl benzene copolymer support was synthesized successfully. The supported catalyst was characterized by elemental analyses, TGA, conductivity and magnetic susceptibility measurements, FT-IR and Diffused Reflectance and Electron Spin Resonance spectral analysis. The proposed catalyst revealed positive outcomes in the oxidation reactions of Phenol, p-Nitrophenol, p-Cresol, Benzyl alcohol and p-Chlorobenzyl alcohol in water under ambient reaction conditions with H2O2 as an oxidant. The catalyst under ideal concentration and ambient reaction conditions exhibited excellent activity towards the green oxidation of Phenol with 99% conversion with 96% selectivity toward catechol at 60 °C. Similarly, p-nitrophenol exhibited a 95% conversion with 86% selectivity toward p-nitrocatechol. Additionally, the oxidation of p-cresol resulted in a 99% conversion and 92% selectivity toward p-hydroxybenzaldehyde. The catalyst also displayed excellent recyclability and facile separation, underscoring its potential for sustainable oxidation processes. It could be recycled for five turns retaining the catalytic activity of 92 to 94% with negligible leaching of only 0.25% of the embedded metal. The results suggested immobilized vanadium complex as an environmentally benign catalytic system to oxidize phenolic compounds in water.