Functionalized Rutile TiO₂(110) as a Sorbent To Capture CO₂ through Noncovalent Interactions: A Computational Investigation

Abstract

The present study evaluates the CO2 adsorption capacity of functionalized rutile TiO2(110), using the density functional theory and ab initio molecular dynamics simulations. The defect-free TiO2 surface is functionalized (f-TiO2) with alkanolamines (AKAs), namely, monoethanolamine (MEA), 3-aminopropanol (3AP), and amino acids (AAs) glycine (GLY) and β-alanine (β-ALA). These functionalized adsorbents attain stability through bifunctional/bidentate binding of weakly acidic OH/COOH groups to TiO2 surface. The AKAs bind parallel to the surface, whereas the AAs bind perpendicular to the TiO2 surface, exhibiting several binding sites favorable for multiple, cooperative noncovalent interactions with CO2. The nature and strength of these interactions are evaluated in terms of binding energies, vibrational frequencies, quantum theory of atoms in molecules (QTAIM) approach, and charge-transfer analysis. The subtle yet substantial interactions of CO2 with f-TiO2 will lead to physisorption and diffusion through pores/channels of f-TiO2-based solid adsorbents, which consequently reduce the energy required for the regeneration process. Among all of the configurations of CO2 binding with f-TiO2, GLY-TiO2···CO2 displays the highest binding energy of −46 kJ/mol, and the trend is follows as: GLY > 3AP > MEA > β-ALA. Finally, this study examines the possibility of f-TiO2-based solid adsorbents as promising materials for CO2 capture at reduced cost in view of their preference toward physisorption of CO2 gas molecules.