Confined Transformation of UiO-66 Nanocrystals to Yttria-Stabilized Zirconia with Hierarchical Pore Structures for Catalytic Applications

摘要

Solid acids as a substitution for hazardous liquid acids (e.g., HF and H2SO4) can promote many important reactions in the industry, such as carbon cracking, to proceed in a more sustainable way. Starting from a zirconium-based metal-organic framework (UiO-66 nanocrystals), herein a transformative method is reported to prepare micro/mesoporous yttria-stabilized zirconia (YSZ) encapsulated inside a mesoporous silica shell. It is then further demonstrated that the resultant reactor-like catalysts can be used for a wide range of catalytic reactions. The acidity of the YSZ phase is found with rich accessible Lewis acid and Bronsted acid sites and they display superior performances for esterification (acetic acid and ethanol) and Friedel-Crafts alkylation (benzylation of toluene). After being loaded with different noble metals, furthermore, hydrogenation of CO2 and a one-pot cascade reaction (nitrobenzene and benzaldehyde to N-benzylaniline) are used as model reactions to prove the versatility and stability of catalysts. Based on the findings of this work, it is believed that this class of reactor-like catalysts can meet future challenges in the development of new catalyst technology for greener heterogeneous catalysis.