Amino-Graphite for Enhanced CO₂ Capture

Expanded graphite (EG) is a three-dimensional material with extremely high porosity and surface area, suitable for amine loading for enhanced selective CO₂ capture. However, amine functionalization of EG is an extremely challenging task, as conventional processes destroy the structure and morphology of EG, reducing CO₂ uptake performance. Herein, a vapor phase deposition (VPD) method has been demonstrated as an effective approach to functionalize EG without requiring treatments such as activation, exfoliation, expansion, etc. Our DFT calculations reveled a strong physical binding between EG and amines. Under optimal conditions, VPD process achieved a 20.18 wt% loading for Tetraethylenepentamine (TEPA)-functionalized EG (TEPA-EG) composite and a 21.92 wt% loading for Triethylenetetramine (TETA)-functionalized EG (TETA-EG) composite. TEPA-EG exhibited a CO₂ capture capacity of 3.48 mmol/g and TETA-EG achieved a capacity between 2.59 mmol/g at 298 K under simulated coal-fired power-plant flue-gas (0.15 bar CO₂) conditions. Furthermore, both TETA-EG and TEPA-EG at 298 K showed dynamic adsorption capacities of 1.89 mmol/g and 1.54 mmol/g under dry conditions and 2.53 mmol/g and 2.06 mmol/g under wet conditions at 298 K, respectively. The cyclic dynamic adsorption runs under both dry and wet conditions and exhibited rapid regenerability without deviation or capacity loss. Additionally, long-term gravimetric adsorption-desorption tests over 75 cycles showed capacity retention exceeding 98%. Overall, the VPD approach proposed in this work holds strong potential for the large-scale preparation of diverse functional materials for a wide array of applications.