Adsorption of greenhouse gases on the surface of covalent organic framework of porphyrin – An ab initio study

Abstract

Porphyrin, a novel and recognized material for its unique properties and complex structure, is considered to be structured into 2-dimensional sheets of covalent organic frameworks. The stability and the functionality of the material is studied using density functional theory. The material is studied for its application as an adsorbing material for greenhouse gases (GHG) and the significant properties are noted. The gas molecules CO, CO2 and CH4 were interacted with the metal free porphyrin sheet (PS) and the efficiency to adsorb CO2 is found to be higher than for the other gas molecules under study. The adsorption energy of CO2 on PS is calculated to be −0.190 eV which is comparatively higher than the adsorption strength of graphene. Similar studies were conducted with porphyrin sheet with ferrous metal ion (PSF) as the adsorbing material. The adsorption strength of PSF for CO2 molecule is −0.914 eV which clearly demonstrates the tunability of the material. The HOMO-LUMO and the orbital localization plot along with the π-electron delocalization pathway confirm the adsorption of GHGs on PS and the efficiency of the material to attract gas molecules. The adsorption spectra confirm the adsorbing nature of both PS and PSF for the adsorption of gas molecules.