Pd nanoparticles on zeolite imidazolide framework-8: Preparation, characterization, and evaluation of fixed-bed hydrogenation activity toward isomeric nitrophenols

Abstract A room-temperature wet chemical method was developed for preparing a catalyst comprising Pd nanoparticles (NPs) supported on a zeolite imidazolide framework-8 (ZIF-8) surface (Pd/ZIF-8). The Pd/ZIF-8 catalyst exhibited a large surface area and high crystallinity, almost equal to those of pristine ZIF-8. The binding of the Pd NPs deposited on the ZIF-8 surface was shown to occur at the ZIF-8 particle surface rather than throughout the metal–organic framework (MOF) structure. The method was also suitable for complexing ZIF-8 with several other, nano-sized noble metals. The Pd/ZIF-8 heterogeneous catalyst was applied in the NaBH₄-reduction of isomeric nitrophenols in both batch and fixed-bed systems. The catalyst was universally active against the isomeric nitrophenols, with a catalytic conversion of 99.7% after 1 h of cycling in the fixed-bed system. Thus, we have demonstrated the preparation of stable, supported catalysts and their application to the continuous reduction of multi-component nitrophenol mixtures.