(649c) Investigation of Preferential CO2 Binding on Lignin-Derived Carbon Quantum Dots through Molecular Dynamics Simulations

To be effective in mitigating global climate change, CO₂ capture at the source of generation from fossil fuel power plants requires a selective adsorbent that can be produced at low cost from an abundant source. Kraft softwood lignin is produced domestically in the tens of millions of tons on an annual basis as a waste stream at pulp and paper mills. This work builds upon experimentally established synthesis routes to create economically viable lignin-based adsorbents for CO₂ capture at the source of generation. The capacity and the selectivity of the adsorbent is modified through decoration of the interior surface using carbon quantum dots (CQDs) also synthesized from lignin. Due to the different quadrupole moments of CO₂, N₂, and O₂, tailoring the charge distribution of the CQDs allows for selective adsorption based on the electrostatic contribution to the binding energy. The charge distribution of CQDs is controlled through either hetero-atom (nitrogen) doping during synthesis or functionalization with amine, hydroxy or carboxyl groups. Classical molecular dynamics simulation is used to investigate the strength of binding and selectivity of CQDs for CO₂, N₂, and O₂, as a function of size, doping and functionalization on several carbon substrate materials at finite temperatures. Selectivity is determined based on a direct statistical analysis of the number of gas molecules interacting with the CQD. This work successfully demonstrates a proof of concept that the charge distribution on CQDs can be manipulated, resulting in changes to the binding and selectivity for CO₂, N₂, and O₂. Optimization the atomic architecture of the CQD as well as the distribution of CQDs on the substrate is underway to identify a viable industrial scale adsorbent for CO₂ capture.