ABSTRACT
Carbon nanocages (CNCs) have attracted tremendous interest in heterogeneous catalysis due to their promising properties of porous structure and improved mass transfer. Nevertheless, the controlled synthesis of CNCs remains a great challenge. Herein, we have shown the successful construction of functionalized N-doped CNCs (NCNCs) via a one-stone-two-birds strategy. The selective use of hexacarbonyl molybdenum (Mo(CO)6) can not only protect the profile of the ZIF-8 precursor from collapse during thermal treatment but also be sacrificed for the functionalization of NCNCs after pyrolysis. Detailed mechanism studies reveal that Mo(CO)6 evolves into MoO3 on the surface of ZIF-8 and then facilitates the rapid pyrolysis of ZIF-8, leading to the formation of NCNCs decorated with small-sized MoC nanoparticles (MoC/NCNCs). The versatility of this one-stone-two-birds strategy has been validated by the generations of Cr- and W-decorated NCNCs. Moreover, MoC/NCNCs can serve as a selective and stable catalyst for furfural hydrogenation. This work provides a facile and universal strategy for fabricating and functionalizing CNCs, which attracts research interest in the fields of chemistry, material science, catalysis, and beyond.
ABSTRACT
Metal-organic frameworks have been exploited as excellent solid precursors and templates for the preparation integrated nanocatalysts with multicomponent and hierarchical structures. Herein, a novel synthetic protocol has been developed to fabricate versatile Zr-based solid solutions (such as ZnO-ZrO2, Co3O4-ZrO2, and CuO-ZrO2) via pyrolysis of Schiff base-modified UiO-66 octahedrons (size <100 nm), which were then utilized as efficient catalysts for CO2 hydrogenation. The Schiff base serves as an effective bridge to dope secondary metal ions into UiO-66 frameworks with controlled amounts of 0.13-8.8 wt %, which are initially hard to achieve. Interestingly, by simply changing the loading metal ions, the selectivity of C1 hydrogenation products can be facilely tuned. For instance, the maximum CO2 conversion of ZnO-ZrO2, Co3O4-ZrO2, and CuO-ZrO2 solid solutions were 5.8, 11.4, and 22.5%, with the main product selectivity of 70% CH3OH, 92.5% CH4, and 86.7% CO, respectively. Moreover, in situ diffuse reflectance infrared Fourier transform spectra characterization reveals that the significant difference in C1 product selectivity is mainly determined by the balance of *HCOO, *CH3O, and *CO intermediate species over the Zr-based solid solutions.
ABSTRACT
An electrospinning with calcination process was employed for the synthesis of La1-xCexCoOδ (x=0, 0.2, 0.4, 0.6, 0.8, and 1.0) oxides. These catalysts were investigated in terms of total benzene oxidation, and characterized by means of XRD, BET, H2-TPR, SEM, XPS, and TEM techniques. The results show that the amount of Ce doping obviously affects the physicochemical and catalytic properties of La1-xCexCoOδ, and when x=1.0, CeCoOδ exhibits the best activity and highly thermal durability for catalytic oxidation of benzene. Additionally, it is demonstrated that the increased activity over perovskite phase dominated oxides is ascribed to a larger surface area while the activity enhancement over metal oxides mainly results from a higher valance of Co and better redox property.
