Nitrogen-Functionalized Ordered Mesoporous Carbons as Multifunctional Supports of Ultrasmall Pd Nanoparticles for Hydrogenation of Phenol

N-functionalized ordered mesoporous carbons could be readily obtained by post-synthesis treatment with nitrogen containing molecules to achieve materials with a nitrogen loading as high as 8.6 wt % and well preserved mesopore structure. Using NH3 as nitrogen source dramatically increased the Brunauer-Emmett-Teller (BET) surface area and pore volume of the resultant hybrid material; however, N-doping with melamine as a source resulted in the contrary results. The N-doped carbons were used as supports to immobilize small-sized Pd nanoparticles (PdNPs), which provided a unique platform to investigate the influence of metal nanoparticle size, mesostructural properties, and N-functionalized supports on the selective hydrogenation of phenol to cyclohexanone, an important intermediate in the production of nylon 6 and nylon 66 in the chemical industry. The catalyst with ultrasmall (about 1.2 nm) PdNPs gave the best reaction activity and selectivity under mild conditions. In addition, the present multifunctional catalyst demonstrated excellent catalytic stability and could be used 6 times without loss of product yields. This outstanding catalytic performance could be attributed to the synergetic effects of mesoporous structure, N-functionalized supports, and the stabilized ultrasmall PdNPs. This work might open new avenues for the development of functionalized catalysts with supported ultrasmall metal nanoparticles and hybrid porous support as well as their clean catalyses.