Controllable Synthesis of Hierarchically Macro-, Meso-, and Microporous UiO-66 for Efficient Catalysis.

Abstract

In recent years, the controllable synthesis of hierarchically porous metal-organic frameworks (HP-MOFs) has received significant attention. However, most synthesized HP-MOFs are primarily adjusted in terms of second-order porosity, and the simultaneous control of mesopore and macropore sizes in HP-MOFs remains difficult to attain. Herein, for the first time, HP-UiO-66-NH₂ is successfully synthesized with simultaneously controllable macro-, meso-, and micropores (MMM-UiO-66-NH₂) by combining the hard template methods and the water-acid competitive nucleation strategy. Impressively, the innovative introduction of a water-acid system can effectively slow down the dissolution of polystyrene (PS) microspheres, ultimately achieving simultaneous regulation of macropore sizes in the range of 160-400 nm and mesopore sizes in the range of 3.9-10.3 nm. Meanwhile, this method can be extended to other UiO-66 series. The hierarchically macro-, meso-, and microporous structure provides sufficient accessibility to substrate molecules and enables rapid mass transfer, contributing to the highest Knoevenagel condensation reaction performance. Furthermore, the MMM-UiO-66-NH₂ is used as an anchoring carrier to bind the bulky phosphomolybdic acid (PMA) through the strong host-guest interaction, endowing it with excellent catalytic oxidative desulfurization (ODS) performance. This study has developed an effective synthetic strategy for preparing HP-MOFs and further expanded the application of HP-MOFs in macromolecular-related catalysis.