Well-Defined MOF-Derived Hierarchically Porous N-Doped Carbon Materials for the Selective Hydrogenation of Phenol to Cyclohexanone

Metal organic framework (MOF) derivatives, porous N-doped carbons (CN), can be used as catalyst carriers owing to their excellent structural properties. The microstructures of MOF-derived carbon materials are affected considerably by the atmosphere in which the parent MOFs are pyrolyzed. In this study, a hierarchically porous N-doped carbon hybrid of carbon nanotubes and a porous carbon framework (denoted CN-H) was fabricated by pyrolysis in a H2/Ar atmosphere followed by acid etching, and subsequently, a Pd@CN-H catalyst was synthesized by the addition of Pd nanoparticles on the porous N-doped carbon support. The pyrolysis atmosphere and etching treatment significantly affected the morphology, specific surface area, meso/macropore ratio, and composition of the porous N-doped carbon materials, as well as the catalytic properties of the Pd@CN catalysts for the selective hydrogenation of phenol to produce cyclohexanone. Nitrogen adsorption-desorption measurements and inductively coupled plasma atomic absorption spectroscopy analyses confirmed that pyrolysis in a H2/Ar atmosphere and acid etching significantly increased the number of meso/macropores in Pd@CN-H, thus enhancing the Pd loading and phenol adsorption. As a result of the increased porosity, Pd loading, and phenol adsorption, the cyclohexanone selectivity and phenol conversion were improved. Furthermore, the as-fabricated Pd@CN-H catalyst displayed good reusability in recycling tests. These results provide insights into the synthesis of MOF-derived hybrid carbon materials and their possible utilization in catalysis.