Solvent-Free Synthesis of Zeolitic Imidazolate Frameworks and the Catalytic Properties of Their Carbon Materials

Abstract

Zeolitic imidazolate frameworks (ZIFs) are traditionally synthesized solvothermally by using cost- and waste-incurring organic solvents. Here, a direct synthesis method is reported for ZIF-8, ZIF-67, and their heterometallic versions from solid precursors only. This solvent-free crystallization method not only completely avoids organic solvents, but also provides an effective path for the synthesis of homogeneous mixed-metal ZIFs. Furthermore, under templating by NaCl/ZnCl₂ eutectic salt, carbonization of the ZIF materials gives rise to a series of N-containing high-surface-area carbon materials with impressive catalytic properties for the oxygen reduction reaction.

Keywords: ZIF-67; ZIF-8; ZIF-Zn/Co; electrocatalysis; oxygen reduction reaction (ORR); solvent-free synthesis; zeolitic imidazolate frameworks.