Copper-induced synthesis of zinc imidazolate metal-organic framework (ZIF-8) crystals and coatings

Zeolitic imidazolate framework-8 (ZIF-8) is one of the most stable Metal Organic Frameworks currently available, with promising properties in adsorption, separation and catalysis. Herein, we report a method for the rapid production of ZIF-8 crystals at room-temperature from methanolic solutions containing sodium acetate and metal salts. Of the different metal salts tested, copper nitrate presence prompted formation of cubic shaped ZIF-8 crystals within 5 min. Derived from this finding, an adaption of the synthesis route was implemented over copper foils and copper based metallic/non-metallic substrates, which yielded high quality shape- and size-controlled ZIF-8 crystal coatings. The outcomes also revealed a significant impact of sodium acetate as modulator and of copper ions released in the reaction media as triggering agent/co-modulator. Together these chemical species are understood to be involved in a multitude of coordination complex formation and deprotonation equilibria, thus largely determining the ZIF-8 crystal morphology and growth, especially near the copper releasing sites. Overall, this work presents an important platform for rapid and controlled synthesis of ZIF-8 crystals and coatings over metallic/non-metallic substrates, which can be adapted for advanced applications such as device integration.