Carbon Aerogels with Excellent CO₂ Adsorption Capacity Synthesized from Clay-Reinforced Biobased Chitosan-Polybenzoxazine Nanocomposites

The present study reports for the first time the use of biobased chitosan-polybenzoxazine (CTS-PBZ) as a precursor for high CO2 adsorbing carbon aerogels (CAs). Montmorillonite (MMT) is used to reinforce the CTS-PBZ aerogel. MMT-CTS-PBZ nanocomposite aerogels are synthesized using the freeze-drying technique and then cross-linked via ring-opening polymerization of benzoxazine followed by carbonization at 800 °C. Polybenzoxazine improves the structural stability for removing CO2 from the environment even at a high pressure. The properties of polymeric and nanocomposite aerogels have been evaluated using X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The microstructure of the CAs is characterized by N2 adsorption–desorption measurements. The CAs exhibit mesoporous materials with pore sizes in the range of 2–7 nm and high BET surface area. The total pore volume of CAs is as large as 0.296 cm3 g–1, and the maximum BET surface area is 710 m2 g–1. Breakthrough curves of CO2 adsorption show high CO2 adsorption capacity at ambient conditions and excellent CO2 adsorption–desorption reversible performance with a maximum of 5.72 mmol g–1. Adsorption isotherms and thermodynamic properties of CO2 adsorption are described.