2D/3D Assemblies of Amine-Functionalized Graphene Silica (Templated) Aerogel for Enhanced CO₂ Sorption

This work investigates the one-pot facile synthesis of novel 2D/3D assemblies containing graphene silica (templated) aerogel sorbents for CO₂ capture, a greenhouse gas of major global concern. In this synthesis, 3D silica (templated) aerogels were formed along the planes of 2D graphene sheets, resulting in 2D/3D assemblies of flake-like shapes. The templates were burnt off from the 2D/3D assembly, leaving a mesoporous cavity which increased with the carbon chain length used in the synthesis method. As such, morphological features related to surface area and total pore volume increased significantly by over 80% as compared to blank (no template) samples and reached maximum values of 734 m² g^-1 and 0.42 cm³ g^-1, respectively. The increase in total pore volume allowed for higher content of impregnated amine into the 2D/3D assembly followed by a freeze-drying method. The CO₂ sorption capacity of the amine-functionalized 2D/3D assemblies reached high values at 4.9 mmol g^-1 (mass over weight ratio), equivalent to 11.67 mmol cm^-3 (mass over total pore volume ratio). The amine-functionalized 2D/3D assemblies were stable over 10 cycles of CO₂ sorption and desorption. Further, heat of sorption results were generally low, with the lowest value reaching 59 kJ mol^-1. These results are desirable for the deployment of 2D/3D assemblies as sorbents to capture CO₂.