Crystal Growth Blocking Strategy Enabling Efficient Solvent-Free Synthesis of Hierarchical UiO-66 for Large-Molecule Catalysis

Metal-organic frameworks (MOFs) with rich hierarchical structures have attracted great attention in processes with large molecules, such as catalysis and adsorption. However, efficiently and cost-effectively fabricating hierarchical MOFs with robust stability remains challenging. Herein, we report a crystal growth blocking strategy to prepare hierarchical UiO-66 by a solvent-free method. The addition of FeCl3 to the synthetic system blocks the overgrowth of UiO-66 crystals and limits the particle size to around just 12 nm. After the removal of Fe by ethanol treatment, these small particles loosely aggregate and gain intercrystalline mesopores. The optimal sample Mes-UiO-66 exhibits a well-developed hierarchical structure, the BET surface area reaches 1161.9 m2 g-1, and the mesopore volume attains a state-of-the-art 1.21 cm3 g-1. The superior catalytic performance and the robust stability of Mes-UiO-66 are demonstrated by the oxidation of DBT, in which the DBT conversion surpasses 99% and shows a slight decrease after five cycles. Our finding may provide a novel platform for efficiently fabricating hierarchical MOFs for large-molecule catalysis.

Automated summary

This study reports a crystal growth blocking strategy for the preparation of hierarchical UiO-66 MOFs using a solvent-free method. The addition of FeCl3 limits the overgrowth of UiO-66 crystals, resulting in particles with a size of approximately 12 nm. After removing Fe, these small particles loosely aggregate and gain intercrystalline mesopores. The optimized sample Mes-UiO-66 exhibits a well-developed hierarchical structure, with a BET surface area of 1161.9 m2 g-1 and a mesopore volume of 1.21 cm3 g-1. The catalytic performance and stability of Mes-UiO-66 are demonstrated by the oxidation of DBT, achieving a DBT conversion of over 99% with only a slight decrease after five cycles. This finding provides a novel platform for efficiently fabricating hierarchical MOFs for large-molecule catalysis.