DFT studies on effects of aminopropyl modification on CO₂ adsorption properties of cellulose

CO₂ emission from fossil fuel combustion is still the main cause of greenhouse effect, designing CO₂ solid adsorbents with high selective adsorbability remains challenging. In this study, cellulose nanofibers were modified by 3-aminopropyltriethoxysilane (APTES) for revealing the adsorption mechanism of CO₂ by APTES modified cellulose aerogel. Based on Density Function Theory(DFT), it was calculated that the adsorption configurations, adsorption energy, and partial density of states of CO₂ on the pristine and modified surfaces, which revealed at the atomic level the mechanism influenced by the APTES grafting. The results indicate that the CO₂ adsorption properties of cellulose are improved with the increasing APTES loading. The method of GGA-PBE is most suitable for the cellulose unit cell in the DFT calculation; two most stable cellulose surfaces (100) and (001) were selected for the adsorption simulation. It is suggested that the pristine cellulose surfaces have extremely weak adsorption energy to CO₂, and the adsorption energy is significantly improved after the aminopropyl modification, and the modified (0 0 1) surface has the lowest adsorption energy, which is-1.766 eV. Projected density of state analysis indicates that the C atom on the (0 0 1) surface produces a lower peak with a wider span. The results of adsorption energy and PDOS jointly prove that after APTES modification, the (0 0 1) surface of cellulose has the strongest adsorption property, which enhances the adsorption properties of cellulose materials.