Exfoliation of layered double hydroxides (LDHs): a new route to mineralize atmospheric CO2

Abstract

Layered Double Hydroxide (LDH) of Mg–Al–Acetate (Mg/Al = 3) was prepared by an anion exchange method starting from a nitrate precursor. The high hydration energy of acetate was exploited to exfoliate LDH into nanosheets having a thickness of 2–3 nm. A colloidal suspension of LDH layers was freeze dried to retain the layers in the exfoliated state. Thermal decomposition of exfoliated LDH at 400 °C resulted in the mixed metal oxide having a surface area of 275 m² g⁻¹ which is higher than pristine LDH oxide (100 m² g⁻¹). This enhanced surface area of exfoliated LDH is responsible for a large amount of CO₂ sorption (1.4 mmol g⁻¹) at room temperature as compared to pristine LDH (0.63 mmol g⁻¹). This enhanced CO₂ uptake is equal to some of the porous solids at similar conditions. The combination of aqueous exfoliation and the freeze drying technique has resulted in the successful synthesis of a novel CO₂ adsorption sorbent based on LDHs.