Dynamic Solvent System as a novel approach in sustainable pyrazolate MOF crystallization

Herein we report a novel and green synthetic approach for pyrazolate-based metal-organic frameworks (MOFs) as demonstrated by the three prominent examples of this material class: [Ni(bdp)]n, and two supramolecular isomers [Zn(bdp)]n and BUT-58 (H2bdp = 1,4-bis(1H- pyrazol-4-yl)benzene). Replacement of dimethylformamide (DMF) by a reactive mixture of 1-butanol and acetic acid enables to avoid toxic chemicals, as well as precise control over the crystal sizes and shapes of the products. Improved crystallinity consequently leads to a more pronounced breathing behavior during nitrogen physisorption. Moreover, flexibility modulation through crystal size engineering becomes within reach. Due to the accessibility to highly crystalline materials, single-crystal X-ray diffraction on the pristine crystals could be performed to elucidate the preferred adsorption sites in the studied frameworks.