We
propose a novel and cyclic synthetic approach for controlling
crystal polymorphs of CaCO3 by using green CO2-responsive switchable solvents which acted as both the CO2 capturer for the carbonate source and the polymorphisms director.
Five solvents were employed, and various reaction conditions such
as calcium resources, calcium concentration, reaction temperature,
and reaction time were investigated. Results show that this developed
framework permits producing any crystalline CaCO3 phases
including metastable vaterite and aragonite in pure phases by selecting
a suitable solvent and adjustment of the reaction conditions. Furtherly,
the mechanism study demonstrates that the solvents attach on the surface
of the primary nanoparticles to selectively control and direct the
growth of any specific polymorph phases. Eventually, the nuclei are
self-assembled into an oriented geometry, allowing the growth and
stability of specific crystals; as such, spherical vaterite, rods,
and shuttle-like aragonite crystals can be obtained. This new configuration
would be an appropriate and an efficient method to apply to large-scale
production, therefore, a promising process attributed to complete
solvent recovery and regeneration of the initial reactants, thus being
an environmentally risk-free route.