Solvothermal synthesis of mixed-ligand metal-organic framework ZIF-78 with controllable size and morphology

ZIF-78 is a prototypical mixed-ligand compound among metal-organic frameworks (MOFs), with the composition of divalent zinc cations bridging by 2-nitroimidazolate (nIm) and 5-nitrobenzimidazolate (nbIm) anions. ZIF-78 belongs to hexagonal space group (P6(3)/mmc) with a GME topology. Owing to the anisotropic pore structure and good affinity to CO2, ZIF-78 has potential applications in adsorption and separation fields. Herein, morphological control of ZIF-78 crystals was achieved via solvothermal synthesis. XRD, SEM, NMR, and adsorption characterizations were performed to study the crystalline phase, morphology, composition and adsorption behavior of obtained crystals, respectively. ZIF-78 micro-crystals with shape of the hexagonal rods were prepared with the assistance of triethylamine. The size and the aspect ratios of ZIF-78 microrods were manipulated from the slender to the squat via varying the nutrient concentration, the ligand concentration or relative molar ratio of nIm to nbIm. (c) 2013 Elsevier Inc. All rights reserved.