CaCO Crystals with Unique Morphologies Controlled by the Hydrogen-Bonded Supramolecular Assemblies of Ureido-Pyrimidinone-Amino Acid Derivatives.

Biomineral materials such as nacre of shells exhibit high mechanical strength and toughness on account of their unique "brick-mortar" multilayer structure. 2-Ureido-4[1]-pyrimidinone (UPy) derivatives with different types of end groups, due to the self-complementary quadruple hydrogen bonds and abundant Ca binding sites, can easily self-assemble into supramolecular aggregates and act as templates and skeleton in the process of inducing mineral crystallization. In this work, UPy derivatives were used as templates to induce the mineralization and growth of CaCO through a CO diffusion method. The morphology of CaCO crystals was modulated and analyzed by adjusting the synthesizing parameters including Ca concentration, pH, and end groups. The results showed that, by the regulatory role of the mineralization template, it was easier to realize the multilayer crystal structure at a lower concentration of Ca (less than 0.01 mol L). Under alkaline regulation, the quadruple hydrogen bonds would be destroyed, and the template's regulation effect on the morphology of CaCO crystals would be weakened. Moreover, by comparing different types of end groups, it was proven that the UPy derivatives with carboxylic acid groups (-COOH) played a crucial role in the process of CaCO crystallization with unique morphologies.