Morphology control in modulated synthesis of metal-organic framework CPO-27

The CPO-27/MOF-74 series is among the most investigated metal-organic frameworks because of their usefulness in a diverse range of applications. For specific applications, it will be important to control the shape and size of the particles or crystallites of the material. The modulation approach has been successfully used to direct these parameters in the synthesis of MOFs. Here, we report the synthesis of CPO-27-Ni in the presence of different ratios of benzoic acid and acetic acid as modulators. Yields, powder X-ray diffraction data, scanning electron microscopy results, and elemental, thermogravimetric, and gas sorption analyses are compared to study the influence of the modulator on the product. The results show that we have successfully synthesized pure CPO-27-Ni independent of the amount of modulator. The modulator affects the resulting morphology of the crystalline product with a defined variation of particle sizes and shapes. In addition, ESI-MS has been employed in probing the reaction solutions. It shows the preferred formation of complexes between the metal cation and the modulator, thus indicating that the ligand substitution plays a major role in the crystal growth.