ZIF-8: A comparison of synthesis methods

• ZIF-8 was prepared by 7 different synthesis methods.
• Physicochemical properties of the samples were compared.
• ZIF-8 with smaller particle size showed better activity in condensation reaction.
• Fe3O4 nanoparticles entrapped in ZIF-8 enabled effective separation in liquid.

A zeolitic imidazolate framework, ZIF-8, was prepared via a variety of synthesis routes: solvothermal, microwave-assisted, sonochemical, mechanochemical, dry-gel, and microfluidic methods. Their textural properties and morphology were examined by surface area measurements and scanning electron microscopy, and compared with those of commercial ZIF-8. Although the BET surface areas fell within a range of 1250–1600 m2 g−1, the particle size of the samples prepared by dry-gel and sonochemical routes were significantly smaller than the others, which led to superior performance in the Knoevenagel condensation reaction. The effective incorporation of magnetic Fe3O4 nanoparticles into the ZIF-8 structure for easy particle separation in the liquid phase was feasible using solvothermal, dry-gel and mechanochemical synthesis methods. Dry-gel and mechanochemical synthesis produced a higher ZIF-8 yield.