Enhanced adsorption of CO₂ on cellulose and chitosan surface by H₂O Co-adsorption

Adsorption of CO₂ on biopolymers such as cellulose (CELL) and chitosan (CS) attracts researchers’ interest, in particular, the aerogel formation with high surface area and unique physical properties. In this work, we studiedthe molecular adsorption of CO₂ molecule on the CELL and CS surfaces by performing density functional theory (DFT) calculations, using dimeric and trimeric structures as model compounds. The structure of the individual CELL and CS along with the molecular adsorbed CO₂ systems CELLCO₂ and CSCO₂ were investigated using B3LYP/6-311++G(d,p) level of theory. The interaction energy of CELLCO₂ indicated a weak physical adsorption process, where CSCO₂ showed higher binding energies. The co-adsorption of CO₂ and H₂O on CELL and CS surfaces was also investigated. The results showed that H₂O stabilized the adsorption of the CO₂ on CELL and CS surface through hydrogen bond (HB), where the adsorption energies increased in the presence of the H₂O molecule. The stability of CELLCO₂ and CSCO₂ was supported by an increase in the charge transfer process. This result highlighted the role of the humidity for the stabilization of CO₂ on biopolymers surface.