Synthesis and characterisation of Pd/MIL68(Al) nanoparticles for high performance catalytic reduction of 4-nitrophenol

The discharge of 4-nitrophenol, one of the most significant, widespread, and hazardous organic pollutants found in industrial wastewater, into clean water resources without undergoing adequate and necessary treatment/conversion processes has become a multidimensional issue that threatens all aquatic life. In this study, the reduction of 4-nitrophenol to 4-aminophenol using an efficient, environmentally friendly, and sustainable method was targeted. For this purpose, Pd/MIL68(Al) catalyst was prepared with 2% metal loading using a simple and conventional wet impregnation method. MIL68(Al), an MOF recently attracting attention due to its superior properties, was synthesised using an efficient and environmentally friendly method as support material in the first step of nanocatalyst synthesis. The prepared Pd/MIL68(Al) catalyst was tested in the reaction of the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH₄ by considering different parameters. In the study where the structure and surface morphology of the Pd/MIL68(Al) catalyst were elucidated using characterisation techniques such as ICP-OES, XRD, SEM, SEM/EDX, TEM, FTIR and XPS, it was determined that Pd(0) nanoparticles were well dispersed on the MIL68(Al) support, with an average particle size of 3.25 ± 0.22 nm. As a result of the interpretation of the data obtained from the study, the TOFinitial value for 4-NP was determined as 43.42 min⁻¹. In the studies carried out to determine the reusability rate of Pd/MIL68(Al) nanocatalyst, it was determined that Pd/MIL68(Al) nanocatalyst exhibited excellent catalytic efficiency and stability (92%) even after five catalytic cycles. Both the simple preparation process, catalytic efficiency, and high reusability rate of the Pd/MIL68(Al) nanocatalyst are the grounds for the evaluation of Pd/MIL68(Al) nanocatalyst as an important alternative for the reduction of 4-nitrophenol and wastewater treatment.