Synthesis of a dual-templated MgO–Al2O3 adsorbent using block copolymer and ionic liquid for CO2 capture

• A dual-templated (P123 + ionic liquid) MgO–Al2O3 adsorbents were prepared.
• Unsaturated O2− ions are active sites for CO2 adsorption.
• CO2 adsorptive performance increased with increasing basicity of adsorbent.
• Medium basicity is the key factor in determining CO2 adsorptive performance.

A dual-templated MgO–Al2O3 (denoted as SI-MA) was prepared by a single-step evaporation-induced self-assembly (EISA) method using P123 and ionic liquid as template. For comparison, P123-templated MgO–Al2O3 (denoted as S-MA) and ionic liquid-templated MgO–Al2O3 (denoted as I-MA) were also prepared by a similar method. The effect of P123 and ionic liquid on physicochemical properties and CO2 adsorptive performance of adsorbents was investigated. All the adsorbents retained well developed mesoporous structure and SI-MA exhibited the highest surface area. It was observed that relative distribution of coordinately unsaturated aluminum increased in the order of I-MA < SI-MA < S-MA. Similarly, the basicity of adsorbent increased in the order of I-MA < S-MA < SI-MA and the highest basicity of SI-MA was due to its highest surface area and the large amount of coordinately unsaturated O2− ions. It was also revealed that the CO2 adsorption capacity under dynamic conditions, decreased in the order of SI-MA > S-MA > I-MA, which is in accordance with the trend of basicity. In conclusion, it was found that SI-MA with the highest basicity retained the maximum CO2 adsorptive performance demonstrating that the basicity of the adsorbents played an important role in determining CO2 adsorption capacity.