Synthesis of novel hybrid mesoporous gold iron oxide nanoconstructs for enhanced catalytic reduction and remediation of toxic organic pollutants

Abstract

The development of highly efficient, rapid, and recyclable nanocatalysts for effective elimination of toxic environmental contaminants remains a high priority in various industrial applications. Herein, we report the preparation of hybrid mesoporous gold–iron oxide nanoparticles (Au–IO NPs) via the nanocasting “inverse hard-templated replication” approach. Dispersed Au NPs were anchored on amine-functionalized iron oxide incorporated APMS (IO@APMS-amine), followed by etching of the silica template to afford hybrid mesoporous Au–IO NPs. The obtained nanoconstructs were fully characterized using electron microscopy, N₂ physisorption, and various spectroscopic techniques. Owing to their magnetic properties, high surface areas, large pore volumes, and mesoporous nature (S_BET = 124 m² g⁻¹, V_pore = 0.33 cm³ g⁻¹, and d_pore = 4.5 nm), the resulting Au–IO mesostructures were employed for catalytic reduction of nitroarenes (i.e. nitrophenol and nitroaniline), two of the most common toxic organic pollutants. It was found that these Au–IO NPs act as highly efficient nanocatalysts showing exceptional stabilities (>3 months), enhanced catalytic efficiencies in very short times (∼100% conversions within only 25–60 s), and excellent recyclabilities (up to 8 cycles). The kinetic pseudo-first-order apparent reaction rate constants (k_app) were calculated to be equal to 8.8 × 10⁻³ and 23.5 × 10⁻³ s⁻¹ for 2-nitrophenol and 2-nitroaniline reduction, respectively. To our knowledge, this is considered one of the best and fastest Au-based nanocatalysts reported for the catalytic reduction of nitroarenes, promoted mainly by the synergistic cooperation of their high surface area, large pore volume, mesoporous nature, and enhanced Au-NP dispersions. The unique mesoporous hybrid Au–IO nanoconstructs synthesized here make them novel, stable, and approachable nanocatalyst platform for various catalytic industrial processes.