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.
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