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.