In-situ preparation of a bismuth-based magnetic composite for catalytic reduction of 4-nitrophenol

The substitution of noble metal-based catalysts by a non-precious metal is of great interest to develop cost-efficient catalysts. However, maintaining the efficiency, good selectivity, and recyclability properties of noble-metal-based catalysts remains a challenge. The present work reports the preparation of a magnetic composite by co-precipitation method, containing a complex mixture of bismuth subcarbonate, bismuth oxide, hydrotalcite-like compounds, and magnesium carbonate on magnetic iron oxide (Mag-MMO). Bismuth species showed a disordered stacking of nanoflakes over the magnetite surface with embedded magnesium carbonate. The composite exhibited high efficiency towards the catalytic reduction of 4-nitrophenol to 4-aminophenol using borohydride as a reducing agent, showing high catalytic activity, with a first-order kinetic constant of 4.05 min−1. During the catalytic reaction, borohydride converted in situ bismuth oxide and bismuth subcarbonate into semi-metallic bismuth. Additionally, the catalyst was easily separated from the supernatant by a magnet and reused for nine more cycles, indicating good cycle stability. The obtained results suggest that Mag-MMO is a promising catalyst for the 4-nitrophenol conversion process, with outstanding cyclical performance.