Synthesis of CaCO3–SiO2 composite using CO2 for fire retardant

•CaCO3 and Ca2SiO4 are widely used fire retardant fillers.•Reducing greenhouse gas is a key issue for environmental concern.•Capturing CO2 gas is a new method to reduce the greenhouse gas.•CaCO3–SiO2 was synthesized by bubbling CO2 into Ca(OH)2 with NH4OH catalyst.•The characteristic FTIR absorption peaks of CaCO3 appeared at 1480, 850, 750 cm−1.