2-Aminothiazole-functionalized triazine-modified polystyrene decorated with gold nanoparticles as composite catalyst for the reduction of 4-nitrophenol

Abstract

Herein, polystyrene (PS) bearing di(2-aminothiazole)-substituted triazine as chelation unit for both Au(III) ions and Au(0) nanoclusters was prepared through successive chemical modification of native polystyrene including nitration (treatment with HNO3/H2SO4), reductive amination (treatment with SnCl2/HCl), and successive grafting of 2,4,6-trichloro-1,3,5-triazine and 2-aminothiazole. The derived gold nanoparticles- (AuNPs-) containing composite material was obtained through chelation of the nanogold precursor, namely hydrogen tetrachloroaurate, and subsequent in situ hydride-assisted reduction providing gold nanoparticles with low size (about 14nm) and spherical shape. It is shown that the presence of 2-aminothiazole-grafted triazine units on the phenyl side groups of PS enables the stable anchoring of the AuNPs while preventing agglomeration. Chemical structure of the PS derivatives was confirmed after each synthesis step by a combination of experimental methods such as infrared and energy dispersive X-ray spectroscopies, elemental analysis, X-ray diffraction and scanning electron microscopy. To highlight the catalytic potential of the so-designed nanostructured catalyst, the reduction of 4-nitrophenol was considered in the presence of a large excess of sodium borohydride as reductant specie. UV–visible spectroscopic monitoring of the progress of the reaction confirmed the pseudo-first order kinetic profile associated with a rate constant as high as 3.07×10−2s−1.