Thermochemical transformation in the single-step synthesis of zeolitic imidazole frameworks under solvent-free conditions.

ABSTRACT

An environmentally friendly and economical route for the synthesis of zeolitic imidazole frameworks (ZIFs) was developed based on the thermal treatment of mixed solid precursors in the absence of solvent and additive compounds. This facile, rapid, and one-step synthetic method involves the heat treatment of a mixture of solid precursors (metal and linker). The solid mixture was transformed into a porous crystalline material without post-treatment and in the absence of any solvent. The synthesized materials are nanocrystals (200-500 nm) with sodalite topology, similar to conventionally prepared ZIFs. The properties of the synthesized materials were evaluated using powder X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, porosity and surface area analysis, gas adsorption, and thermal gravimetric analysis. The metal-oxide precursor, which is typically considered to be inert in the context of chemical synthesis, was readily transformed into a ZIF using this thermochemical method. The developed solvent-free, fast, and eco-friendly synthetic method for the preparation of porous ZIFs may be applicable for large-scale industrial synthesis.