Synthesis of p-aminophenol from p-nitrophenol reduction over Pd@ZIF-8

p-Aminophenol was synthesized by the catalytic reduction of p-nitrophenol over Pd@ZIF-8 prepared by an assembly method that involves the construction of ZIF-8 crystals around the pre-synthesized polyvinylpyrrolidone (PVP)-stabilized palladium nanoparticles. The catalyst was characterized in detail by XRD, FESEM, HRTEM, XPS, ICP, N-2 sorption, TGA and FT-IR. The analysis results show that the hybrid material Pd@ZIF-8 has a rhombic dodecahedral structure like ZIF-8, the particle size of Pd@ZIF-8 is about 400 nm, which is much greater than that of ZIF-8 due to the promotion of PVP, and the pre-synthesized Pd nanoparticle with a diameter of 2-5 nm can be well dispersed within the ZIF-8 crystals. The as-prepared Pd@ZIF-8 catalyst exhibits much higher catalytic activity than the commercial Raney Ni in the reduction of p-nitrophenol to p-aminophenol, and can be reused at least five times without obvious loss in catalytic activity. Furthermore, the Pd@ZIF-8 shows outstanding catalytic selectivity for the synthesis of p-aminophenol, and only target product p-aminophenol is formed in the p-nitrophenol reduction. The better catalytic performance of Pd@ZIF-8 may be caused by the small size and high dispersion of Pd nanoparticles confined within the ZIF-8 framework.