Fe₃O₄@MOF hybrid for supercilious recovery of Au(III) and Pd(II) from e-waste and spent as catalysts for cyclohexane oxidation

Improving the economic viability of the most successful precious metal catalysts is one of the significant challenges in renewable energy production. We designed a magnetic hybrid material based on Cu-pPDA MOF and Fe₃O₄ nanosphere for selective recovery of Au(III) and Pd(II) from e-waste. Owing to its superior maximum adsorption capacities of 1450 and 1236 mg/g for Au (III) and Pd(II), respectively, at 45 °C with the pH of 3 and 1, the sorbed samples were converted into catalysts through an annealing process to obtain carbon supported FeAu and FePd nanoparticles catalysts (FeAu/C and FePd/C). Furthermore, these catalysts were applied for the oxidation of cyclohexane and resulted that FeAu/C catalyst exhibited higher conversion rate of cyclohexane (93.2%) than FePd/C catalyst (88.3%). Mechanistic investigations suggested that synergetic effect of Fe and Au on the supported carbon promoted better bond cleavage of the O–O bond in cyclohexyl hydroperoxide, a crucial intermediate species in the oxidation of cyclohexane. This study provides an alternate approach for the sustainable preparation of highly desired catalytic materials.