Phenol Catalytic Hydrogenation over Palladium Nanoparticles Supported on Metal‐Organic Frameworks in the Aqueous Phase

Metal‐organic frameworks (MOFs) have been extensively applied as supports in hydrogenation catalysis owing to their topological structure and high hydrogen storage capabilities. Pd nanoparticles (NPs) supported on a hollow box‐shaped MOF were prepared for phenol hydrogenation in the aqueous phase. The MOF preparation modulated by monocarboxylic acids grow into different structures. MOF140‐AA, modulated by acetic acid at 140 °C, presents the structure of regular cube with a smooth surface. Compared to other supports, Pd NPs supported on MOF140‐AA presents high phenol conversion due to the high hydrogen storage capability of MOF140‐AA. Phenol is completely converted to cyclohexanol over Pd/MOF140‐AA reacted at 260 °C for 2 h with high selectivity. The reaction mechanism of phenol hydrogenation is studied by density functional theory (DFT). The phenol hydrogenation mechanism is calculated on a Pd38 cluster, which describes the reaction pathway consistent with experimental results. Hex, hex, hex! Phenol hydrogenation mechanism was divided into two pathways. The main pathway is phenol firstly hydrogenate to cyclohexanone and then continuously hydrogenate to cyclohexanol. The side pathway is phenol directly hydrogenate to cyclohexanol. Finally, a part of cyclohexanol converts to cyclohexane.