Hydrogen bonding to graphene surface: A comparative computational study

Theoretical computations employing the M06-2X, PBE0-D3, omega B97X-D, and B3LYP-D3 density functionals combined with the 6-311++G(d,p) basis set are applied in investigating the adsorption of methanol on pristine graphene. The fragment approach in modeling the graphene surface is applied. Three types of fragments are considered: C36H16, C54H18, and C66H22. Comparative studies on the interactions of benzene and coronene with methanol reveal the electronic factors of the monomeric species governing the adsorption process. The shifts of methanol O-H and methyl stretching frequencies upon complex formation indicate that the adsorption is realized via O-H...pi and C-H... pi hydrogen bonds with the pi-electronic systems of these structures. Comparison with experimental Delta nu(OH)exp shifts for benzene shows that the basicity of the graphene surface is slightly lower than that of benzene. Computed Hirshfeld charges and electrostatic potentials at the ring carbon atoms of the monomeric species reveal the electronic factors associated with the frequency shifts resulting from the complex formation. The effects of the aromaticity of the participating rings on interaction energies and the spectroscopic properties are also considered.