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

Parameswari, Akshinthala, Soujanya, Yarasi, Sastry, G. Narahari
Journal of physical chemistry 2019 v.123 no.6 pp. 3491-3504
adsorbents, adsorption, binding sites, carbon dioxide, density functional theory, energy, ethanolamine, molecular dynamics, quantum mechanics, simulation models, titanium dioxide
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.