Enhanced catalysis of Au/TiO2 for transfer hydrogenation of unsaturated nitro compounds by surface engineering

Abstract

Transfer hydrogenation of unsaturated nitro compounds by NH3BH3 is an important hydrogenation reaction. Among them, Au/TiO2 catalysts could achieve good activity for this reaction, but often have problem such as the selectivity decline. In this study, we prepare PVA-wrapped Au nanoparticles, and then load them onto TiO2 support to obtain Au/TiO2 catalyst. We demonstrate that the prepared catalyst after calcination has achieved high activity (>99 %) and high selectivity (99 %) in the transfer hydrogenation of 4-nitrostyrene (4-NS) within 30 min by NH3BH3 under ambient temperature and pressure. In addition, the catalyst can still maintain high selectivity (>97 %) after being recycled for 5 times, showing its remarkable stability and reusability. Characterization results and density functional theory (DFT) calculations showed that the presence of Au-OH species accelerates the dehydrogenation of NH3BH3 and thus enhances the catalytic activity. Meanwhile, Au-OH species and low-coordinated Au are beneficial to enhance nitro adsorption and improve the selectivity of transfer hydrogenation reaction. This study provides new ideas for the rational design of high-performance green gold catalytic transfer hydrogenation reactions.