Facile synthesis of zeolitic imidazolate framework-8 (ZIF-8) by forming imidazole-based deep eutectic solvent

We report here the synthesis of ZIF-8 with “deep eutectic method”, a mild, efficient and environmentally friendly alternative to conventional synthesis that is carried out near room temperature, no organic solvent and at a stoichiometric molar ratio of zinc salt and imidazole. Deep eutectic method draws inspiration from the feasible formation of Deep eutectic solvent between quaternary ammonium salt and imidazole. The synthesis was performed by simply heating the mixtures of zinc salt, imidazole and quaternary ammonium salt, the hydrogen bond interaction between quaternary ammonium salt and 2-Mim could facilitate the deprotonation of 2-Mim, then promote the coordination between 2-Mim and Zn2+ and accelerate the nucleation and growth of ZIF-8. Particularly, the ZIF-8 synthesized by deep eutectic method possesses a co-existence of micropores and mesopores due to the template role of quaternary ammonium salt. Furthermore, The ZIF-8 synthesized by deep eutectic method exhibited higher capacity for the adsorption of CO2 than ZIF-8 prepared by conventional solution-based method due to its high surface area and large pore volume.