Fabrication of gold nanoparticles within hierarchically ZSM-5-based micro-/mesostructures (MMZ) with enhanced stability for catalytic reduction of p-nitrophenol and methylene blue

Abstract

Gold nanoparticles (Au NPs) have received great attention in diverse catalytic reactions due to their excellent activity. However, the activity is severely relying on dispersion and size of Au NPs. Therefore, regulation of Au NPs for degradation of organic pollutants in water is of vital significance for environmental remediation. Herein, we developed microporous/mesoporous silica, MMZ, using ZSM-5 (SiO2/Al2O3 = 28) as structural constructing precursor and cetyltrimethylamoniumbromide (CTAB) as template via sequential dissolution-self-assembly strategy. The Au precursor is introduced into MMZ and ZSM-5 by ultrasound assisted impregnation and subsequent reduced for Au0 formation. The obtained materials were characterized by XRD, TEM, XPS, SEM, UV-DRS, N2 adsorption and TG/DTG techniques. XRD and TEM study revealed that up to1.0 wt% of Au can be well dispersed with smaller size of 2.8 nm in the material from MMZ (denoted as 1.0Au/MMZ), while serious aggregation and formation of large Au NPs occurs over ZSM-5 with the same Au loading (denoted as 1.0Au/ZSM-5). Catalytic studies also demonstrated that Au/MMZ has much higher catalytic activity for reduction of p-nitrophenol (P-NP) and methylene blue (MB) to p-aminophenol (P-AP) and leuco methylene blue compared with Au/ZSM-5 analogue and other reported Au-based catalysts previously. Moreover, Au/MMZ has good reusability and showed no change in its original catalytic performance till 7th cycles in reduction of P-NP and MB, which is attributed to stable structure and well dispersion of Au NPs over MMZ. Therefore, compared with other Au based catalysts used for catalytic reaction, this Au/MMZ is cheap and promising for industrial applications.