We present the facile synthesis of Co and Zn biomimetic complexes inside the mesoporous silica (MS) nano cages. These biomimetic complexes (Co-Im@MS and Zn-Im@MS) mimicked the active site of carbonic anhydrase and showed an enhanced catalytic activity in CO2 hydration. Furthermore, a partial hydrophobic environment imposed by hexadecanol functionalization, enhanced the activity of Co-Im@MS and Zn-Im@MS. The hexadecanol functionalized Co-Im@MS and Zn-Im@MS, therefore, represent true models for carbonic anhydrase, in which the complexes catalyses CO2 hydration. The hexadecanol moiety could be suggested as a positive modulator for the enhancement of CO2 hydration. BET, FE-SEM, FE-TEM, Si-29 NMR, FTIR, UV-vis DRS, XRD and XPS were applied for the characterization of the functionalized supports and the biomimetic catalysts. The synthesized catalysts were applied to in vitro CaCO3 crystallization and resulted in the morphologically altered CaCO3. We believe that this study will facilitate the development of optimized model systems in the field of biomimetic catalysis. (C) 2014 Elsevier B.V. All rights reserved.