Spray synthesis of Pd nanoparticle incorporated HKUST-1, and its catalytic activity for 4-nitrophenol reduction

In this study, we synthesized Pd nanoparticles incorporated into a HKUST-1 metal–organic framework (Pd/HKUST-1) via a recently developed spray synthesis method and evaluated their catalytic activity. Spray synthesis is a method for obtaining MOFs in a short time by MOF precursor solution spraying and subsequent heating. The synthesized Pd/HKUST-1 is characterized via transmittance electron microscopy (TEM) with energy dispersive X-ray spectrometry, inductively coupled plasma atomic emission spectrometry, X-ray diffraction, and N₂ adsorption measurements. TEM results revealed that Pd nanoparticles were well dispersed in HKUST-1. Pd/HKUST-1 with varying Pd nanoparticle concentrations were obtained by varying the number of commercial Pd nanoparticles in the HKUST-1 precursor solutions. The BET surface area of Pd/HKUST-1 was up to 1069 m²/g. The reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with NaBH₄ was performed using Pd/HKUST-1 as a catalyst. Moreover, the reaction rate of the 4-NP reduction is up to 160 s^–1 g^?1, which is the highest rate constant among the Pd/MOFs.