Here we report a scalable and template-free production strategy in the synthesis of a mesoporous calcium carbonate, which undergoes self-assembled nanostructure formation through a temperature-induced aggregation and polymorphic transformation of the colloids. The specific surface area and pore size distribution of resulting mesoporous calcium carbonate are clearly different depending on the aging temperature. The specific surface area and average pore size for aging temperature of 293 K are 207.3±9.8 m 2 /g and 8.8±0.6 nm, respectively, and 65.1±10.1 m 2 /g and 19.9±2.6 nm at 473 K. Additionally, we apply the mesoporous calcium carbonate powder to formaldehyde vapor adsorbent. We measure the adsorbed amount of gaseous formaldehyde and find that the vaterite-rich powder has larger adsorption per unit area than the calcite-rich one.