Coassembling Mesoporous Zeolitic Imidazolate Frameworks by Directed Reticular Chemistry

Abstract

Conventional microporous zeolitic imidazolate frameworks (ZIFs) face limitations in mass transfer and pore accessibility when dealing with large guest molecules. Here, we describe a technique for the synthesis of mesoporous ZIFs (MesoZIFs) using a strategy we term directed reticular chemistry. MesoZIF-8 was prepared through solvent evaporation-induced coassembly of polystyrene-block-poly(ethylene oxide) (PS-b-PEO), ZIF-8 building blocks, and acetic acid (AcOH), followed by amine-facilitated crystallization of ZIF-8 in the interstices of PS-b-PEO micelles. AcOH prevents the fast coordination of ZIF-8 building blocks, avoiding phase separation during coassembly. The employed amine plays a crucial role in neutralizing the crystallization environment and further deprotonating the 2-methlyimizale linker to coordinate with zinc ions. Ink bottle-shaped mesopores with tunable mesopore sizes were created by adjusting the molecular weight of PS-b-PEO. Compared to microporous ZIF-8, MesoZIF-8 exhibited enhanced performance in Knoevenagel condensation reactions involving large reactants and hydrogen storage capacity. With this study, we establish an efficient approach for synthesizing MesoZIFs with highly accessible mesopores to enhance ZIF performance in targeted applications.