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 N-2 BET analysis. Such mesoporous LDH possesses large mesopores (18 nm) and a high surface area (103 m(2) 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 degrees C and 1 atm and it can be further increased up to 1.21 mmol g(-1) by doping with 20 wt% K2CO3.