Capacity and Selectivity for Carbon Dioxide on Lignin-Derived Adsorbents via Molecular Simulation

In pursuit of cost-effective and environmentally benign materials for carbon capture applications, this study investigates the effectiveness of carbon quantum dots (CQDs) and lignin-derived carbon composites as sustainable materials for selective carbon dioxide capture. Classical grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations are employed to examine the adsorption behavior, binding energy, and selectivity of different functionalized CQDs on graphite and lignin-based carbon composite (LBCC) substrates. Four types of CQDs were studied: amine-functionalized, nitrogen-doped, carboxyl-functionalized, and hydroxyl-functionalized. Our simulations reveal that while all CQD types preferentially adsorb CO₂ over N₂ and O₂, their performance varies significantly depending on functionalization type and surface density. Notably, bare LBCC substrates demonstrate remarkably high CO₂/N₂ and CO₂/O₂ selectivity (>50) in both dry and wet flue gas mixtures at 1 atm pressure. Addition of CQDs to LBCC substrates can increase capacity without reduction in selectivity in dry flue gases. Our findings suggest that an optimized lignin-based activated carbon decorated with specific CQDs could offer a renewable, cost-effective solution for industrial carbon capture.