In the present work, the interaction of dichloromethane (CH2Cl2) and chloroform (CHCl3) on C20 and C19T (T = Cr, Ti, Fe, Ni) has been studied by density functional theory (DFT). The results have been investigated by binding energy, net charge transfer, electrical and thermodynamic properties, and frontier orbitals. Although the complexes of CH2Cl2 and CHCl3 on free C20 nanocages showed slightly binding energy (- 0.029 and - 0.006 eV, respectively), doping of Cr, Ti, Fe, Ni transition metal atoms on C20 nanocage improved the binding energy. The best binding energy was attributed to the adsorption of CH2Cl2 on C19Cr (- 0.755 eV). Based on ESP maps, doping of Cr, Ti, Fe, and Ni is the cause of strong electrophilic region creation which is very useful for adsorption process CH2Cl2 and CHCl3 on nanocages. Also, natural bond orbital (NBO) analysis showed that the best charge transfer was 0.253 eV which was related to the formation of C19Fe-CHCl3 complex. In addition, the least HOMO-LUMO energy gap between free nanocages (C20, C19Cr, C19Ti, C19Fe, and C19Ni) is 4.05 eV (C19Ti). The thermodynamic investigations indicated that due to the negative enthalpy, all of the studied adsorption processes were exothermic.
Keywords: Adsorption study; C20 nanocage; DFT; Enthalpy; HOMO and LUMO; Metal doping.