DFT and TD-DFT studies of halogens adsorption on cobalt-doped porphyrin: Effect of the external electric field

Abstract

DFT and TD-DFT calculations are employed to examine the adsorption of halogen atoms (F, Cl, and Br) and molecules (F2, Cl2, and Br2) on cobalt-doped porphyrin (CoP). The impact of an external static electric field (EF) on the adsorption and the UV–Vis spectra is studied. The adsorption of halogen atoms as well as F2 molecule is chemisorption in the range from −1.14 to −2.41 eV while the adsorption of Cl2 and Br2 is physisorption. The adsorbate–substrate interaction reduces the HOMO-LUMO gap (Eg) to be 1.79–2.72 eV compared to 3.11 eV for CoP. The EF controls the adsorption process where the positive EF improves the corrected adsorption energy (Eadscorr.) while the negative EF attenuates the Eadscorr.. Additionally, the positive EF leads to a decrease in the Eg while, the negative EF increases the Eg. Consequently, for sensing purposes, high sensitivity and low response time are expected for the CoP at the positive EF while negative EF encourages the desorption process and decreases the recovery time. The CoP is optically active with λmax of 494 nm. The UV–Vis spectra analysis shows that the adsorption of halogen atoms causes a blue shift of λmax to be 394, 488, and 491 nm while the adsorption of halogen molecules causes a red shift of λmax to be 892, 846, and 698 nm, respectively. The λmax for adsorbate–substrate complexes is affected by the EF. Our results declare that the cobalt-doped porphyrin may be utilized as a candidate sensor for the considered halogen atoms and molecules.

Keywords

• Adsorption
• Halogens
• Cobalt-doped porphyrin
• DFT
• Electric field
• UV–vis spectrum