Synthesis, morphology control, and properties of porous metal–organic coordination polymers

A “direct mixing” synthesis strategy has been demonstrated for the first time that allows fast (e.g., 0.5 h) synthesis of bulk quantity of thermally stable and highly porous metal–organic coordination polymers (MOCP) nanocrystals (30–150 nm diameter) at room temperature with high yield (∼90%). The MOCP materials constructed from Zn(NO3)2·6H2O and 1,4-benzenedicarboxylic acid (H2BDC) were characterized with scanning electron microscope, powder X-ray diffraction, thermal gravimetric analysis, FT-IR, and volumetric Ar adsorption/desorption. The direct mixing method also produced a highly porous nanometer-sized MOCP material, which is likely to be a new phase that has not been discovered by the more commonly used “diffusion” approach. “Soft” and “hard” template approaches were used to successfully manipulate the morphology of MOCP materials at nanometer scale. In addition, water molecules were shown to play an important role in the synthesis and eventual composition of MOCP materials. Exposure of MOCP materials to water resulted in dramatic drop in surface area and porosity because of possible hydrolysis of the framework. An acid hydrolysis process of MOCP materials was also revealed in which the crystals could be hydrolyzed back into metal salts and organic acid under acid treatment.