Facile synthesis of zeolitic imidazolate framework-8 from a concentrated aqueous solution

• ZIF-8 prepared from stoichiometric metal and ligand aqueous solutions.
• The role of ammonium hydroxide for ZIF-8 preparation was discussed.
• Concentrated precursor solution was used to prepare ZIF-8.
• Highly thermally stable ZIF-8 crystals with uniform shapes and high surface areas.

This paper reports a facile method for the synthesis of zeolitic imidazolate framework-8 (ZIF-8) at room temperature in 10 min. ZIF-8 crystals were produced from stoichiometric metal and ligand (1:2) concentrated aqueous solutions in the presence of ammonium hydroxide. The resulting ZIF-8 crystals possessed high surface area, large micropore volume, and had a truncated cubic morphology with an average particle size of ca. 0.7 μm. TGA and XRD results revealed the structural stability of the as-synthesized ZIF-8 up to 250 °C. The addition of an appropriate amount of ammonium hydroxide was proved to be essential for the formation of ZIF-8 crystal through deprotonation and coordination reaction. Furthermore, ZIF-8 crystals were successfully prepared from different zinc sources, and this method is promising for large-scale synthesis of ZIFs.

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