Coral-mimetic production of aragonite films from CO2 captured by biogenic polyamines

Abstract

We designed CaCO₃ films comprised of aragonite nanorods by mimicking the microstructure and the formation process of the calcareous skeleton of a stony coral in the sea. Hierarchically structured calcareous frameworks are produced from the center of calcification (COC) under alkaline conditions in the organism. In the first step, a seed layer consisting of crystalline nanoparticles was produced as an artificial COC on a polyvinyl alcohol sheet in a solution containing Ca²⁺ ions, polyacrylic acid, and a biogenic polyamine, such as putrescine, through the gradual absorption of atmospheric CO₂. In the second step, aragonite nanorods grew on the artificial COC in the mother liquid obtained by mixing a putrescine solution saturated with CO₂ and a CaCl₂ solution containing Mg²⁺ and alginate. Finally, we obtained a dense, homogeneous film consisting of aragonite nanorods similar to the coral skeleton through the fixation of CO₂.