English Abstract
ABSTRACT :
Adsorption of small gaseous molecules on the center and edges of polycyclic aromatic hydrocarbons is studied through density functional theory calculations. The choice of selected functional for the study is based on a benchmarking, where 37 functionals are evaluated at low cost basis set against high level DFT SAPT calculations for adsorption of water molecule on coronene and hexabenzocoronene. After benchmarking, the detailed analysis is performed for the adsorption of H2S, H2O, NH3, CH3OH, HCN, H2O2 and NH2NH2 on coronene at its center and edges. The coronene is chosen to better elucidate the edge effect on the adsorption of analytes. All of the studied analytes are physiosorbed on coronene with adsorption energies ranging from 1 to 6 kcal mol− 1. These com plexes are stabilized by X-H—π interactions between analytes and coronene surface. The SAPT0 analysis reveals that the X-H—π interactions at the center (non-edge) position of coronene are dominated by dispersion inter
action whereas the similar interactions at the edges are dominated by electrostatic interactions. The change from dispersion to electrostatic on edges is attributed to polarization of the systems by C–H polarity differences. The complexes having lone pair—π interactions have unexpectedly repulsive electrostatic interactions in H2S@GNF and NH3@GNF complexes. Electronic properties reveal that coronene surface is highly selective for hydrazine whereas adsorption of other analytes does not bring any significant changes in the electronic structure of coronene. The high selectivity of coronene for NH2NH2 is also evident from the redistribution of densities in frontier molecular orbitals. For NH2NH2@GNF complexes, the HOMOs are present on hydrazine whereas LUMOs are present in coronene. For other analytes, HOMOs and LUMOs are present merely on graphene nanoflake. This high sensitivity of coronene for hydrazine is due to better overlap of frontier molecular orbitals of analyte with coronene.
