Facile synthesis of bimetallic MOF crystals with controllable morphology and topology by the self-converted strategy of hydroxy double salts (HDSs)

Abstract

Controllable synthesis of metal organic frameworks (MOFs) crystals with definite morphology and topology plays an important role in determining the property and application of MOFs materials, especially bimetallic MOFs which have exhibited an improved performance in many fields due to the incorporation of the second metal ion. Herein, we for the first time report a simple and convenient method of the self-conversion of hydroxy double salts (HDSs) for synthesizing bimetallic MOFs with controllable morphology and topology by merely adjusting the synthesis conditions. As the sample, we employed Zn/Co-HDS as metal source and 2-methylimidazole (HMeIm) and 2-ethylimidazole (HEtIm) as organic ligands, respectively, to investigate the effects of the synthesis conditions on the morphology and topology of Zn/Co bimetallic MOF. The arbitrary transformation with two topologies (SOD and dia) and four morphologies (2D nanosheets, rhombic dodecahedron, truncated rhombic dodecahedron and truncated cubes) of the bimetallic Zn/Co(MeIm)2 was achieved by adjusting synthesis solvent, reaction time and ligand concentration. Analogously, three other topologies (ANA, RHO and QTZ) were also discovered in the bimetallic Zn/Co(EtIm)2 by simply adjusting the synthesis conditions. It is thought that the different synthesis conditions in the preparation of bimetallic MOFs are closely related to the supersaturation of crystal growth unit, thus affecting the morphology and topology of the products. Therefore, this novel synthesis strategy is highly efficient for preparing bimetallic MOFs with controllable morphology and topology.