Calculations were performed with the PBE functional and all-electron def2-SVP basis sets in the ORCA 4.1 program . Dispersion force corrections for self-consistent field energies were included with the DFT-D3 method (with the Becke-Johnson damping function) . The SMD solvation model was used to include solvent effects in water (ε=80.4), which is based on the charge density of a solute molecule interacting with a continuum description of the solvent . Molecular structures were optimized without geometrical constraints; convergence tolerance values of 1×10 -8 and 1×10 -6 Ha were used for SCF and geometry optimization steps, respectively. The adsorbent-adsorbate stability was characterized by the adsorption energy (Eads):