CO2 is a stand-alone molecule. Graphene is a molecular orientation which forms sheets and therefore, different sharing of electrons between molecules to form bonds that hold them all together.
I know that. But when you oxidize it, it becomes CO2. There are no other options. The crystal breaks apart and combines with the oxygen in the only way it can. The bonds that form the crystal now bond with the oxygen.
I would now have to guess that the material is not fully oxidized.
When I oxidize it, I’m going all the way! It will be fancy coal to me. ;-D