MO-ZrO (M = Zn, Co, Cu) Solid Solutions Derived from Schiff Base-Bridged UiO-66 Composites as High-Performance Catalysts for CO Hydrogenation.

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-ZrO, CoO-ZrO, and CuO-ZrO) via pyrolysis of Schiff base-modified UiO-66 octahedrons (size <100 nm), which were then utilized as efficient catalysts for CO 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 C hydrogenation products can be facilely tuned. For instance, the maximum CO conversion of ZnO-ZrO, CoO-ZrO, and CuO-ZrO solid solutions were 5.8, 11.4, and 22.5%, with the main product selectivity of 70% CHOH, 92.5% CH, and 86.7% CO, respectively. Moreover, in situ diffuse reflectance infrared Fourier transform spectra characterization reveals that the significant difference in C product selectivity is mainly determined by the balance of *HCOO, *CHO, and *CO intermediate species over the Zr-based solid solutions.