Imidazolium salts facilitate mechanochemical synthesis of well-dispersed MFI zeolite crystals with c-axis orientation

The mechanochemically-assisted solvent-free (or minimal-solvent) method, compared with the traditional hydrothermal method , exhibits the merits of reduced waste generation, high yields, and fewer safety problems, thus offering new opportunities for the green fabrication of zeolitic materials. This promising synthetic strategy, however, tends to suffer from a severe aggregation of zeolite crystals. Herein, we report the synthesis of a series of well-dispersed MFI-type zeolites with various compositions via a mechanochemical route using imidazolium ionic liquids as additives. The crystal dimensions along a -, b -, and c -axis of the obtained coffin-like silicalite-1 zeolites can easily be controlled by varying the concentration of ionic liquids or the alkyl chain length of ionic liquid cations. This imidazolium ionic liquids-assisted mechanochemical approach can also work equally well with the heteroatom-containing MFI zeolites (e.g. Al-MFI and B-MFI). In addition, it is found that the imidazolium ionic liquid can be recycled for further use.