Abstract This work study the interaction of a toxic substance, formaldehyde, with a F@graphene layer. Using density functional theory, three cases of adsorption of formaldehyde, CH 2 O, on a finite sheet of graphene with 32 carbon atoms are shown. In the first two cases, the formaldehyde is adsorbed on the graphene sheet. The third case shows that under certain conditions it is possible to dissociate the formaldehyde molecule in the HF dimer and the formyl molecule, CHO. Although there are studies that report the toxicity of formaldehyde, it remains to be seen whether the toxicity of the CHO fragment in the reaction, F + CH2O → HF + CHO, may or may not be less than that of formaldehyde.