Synthesis of nano-sized spherical Mg₃Al–CO₃ layered double hydroxide as a high-temperature CO₂ adsorbent

Due to its layered structure, layered double hydroxides (LDHs) generally prefer to form either “sand rose” or platelet-like morphologies. To the best of our knowledge, nano-sized spherical LDHs have not been previously reported. In this work, we present the first successful synthesis of nano-sized spherical Mg₃Al–CO₃ LDH using a facile isoelectric point (IEP) method. SEM and TEM analyses confirmed that the size of the nanospheres is very uniform, with an average value of ca. 20 nm. Furthermore, a mesoporous LDH sample composed of the above synthesized uniform nano-spheres can be prepared, and this material showed a H1 type hysteresis loop in the N₂ BET analysis. Such mesoporous LDH possesses large mesopores (18 nm) and a high surface area (103 m² g⁻¹), which we believe make it a promising adsorbent, catalyst, or support material. We demonstrated that its CO₂ capture capacity is 0.83 mmol g⁻¹ at 200 °C and 1 atm and it can be further increased up to 1.21 mmol g⁻¹ by doping with 20 wt% K₂CO₃.