Synthesis of mesoporous SrCO3 spheres and hollow CaCO3 spheres in room-temperature ionic liquid

Mesoporous SrCO3 spheres with diameter ranging from 200 to 400 nm were synthesized via refluxing the solution of SrCl2 · 6H2O and sodium hydroxide in 1,1,3,3-tetramethylguanidinium lactate at 140 °C in the presence of CO2. The morphology and structure of the as-prepared products were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Nitrogen sorption measurements revealed that the obtained products exhibited high BET surface area of 69.4 m2 g−1 and average pore size of 5.7 nm with narrow pore size distribution. For comparison, CaCl2 was used to synthesize CaCO3 at the same experimental conditions, resulting in hollow calcite spheres and peanut-like structure calcite whose shell thickness and core diameter were about 100 nm and 200 nm, respectively. The BET surface area of the hollow calcite spheres calculated from N2 adsorption is 17.03 m2 g−1.