Emulsion based solvothermal synthesis of CuO grainy rod via the formation of quasi-quadrangular prism shaped Cu2(OH)3Br for recyclable catalyst of 4-nitrophenol reduction

Abstract Quasi-quadrangular prism shaped Cu2(OH)3Br particles were synthesized by emulsion based solvothermal process followed by their transformation to hierarchical copper oxide grainy rods by calcination at 450 °C/2 h. In this process, we employed cetyltrimethyl ammonium bromide (CTAB) as cationic surfactant as well as bromide source, 1-butanol as co-surfactant, cyclohexane as organic (oil) medium, copper acetate as aquo-based copper precursor and hexamethylenetetramine ((CH2)6N4) as the source of ammonia under hydrolyzing condition. The length/diameter of hierarchical CuO grainy rods was found to be around 2.5–10 μm/0.5–1.5 μm comprising of smaller grain (20–30 nm) assembly. The proposed reaction trajectory based on anion-exchange mechanism was proposed for the transformation of Cu2(OH)3(CH3COO) to Cu2(OH)3Br. The product showed excellent catalytic performance for 4-nitrophenol reduction. The apparent rate constant values increased from 0.532 min−1 to 1.038 min−1 with catalyst amount increased from 1 to 3 mg. This investigation refers the novel synthesis approach of CuO grainy-rod from quasi-quadrangular prism shaped Cu2(OH)3Br precursor, and its role as catalyst for 4-nitrophenol reduction.