Provided is a method of producing isolated graphene sheets directly from a carbon/graphite precursor. The method comprises: (a) providing a mass of halogenated aromatic molecules selected from halogenated petroleum heavy oil or pitch, coal tar pitch, polynuclear hydrocarbon, or a combination thereof; (b) heat treating this mass at a first temperature of 25 to 300° C. in the presence of a catalyst and optionally at a second temperature of 300-3,200° C. to form graphene domains dispersed in a disordered matrix of carbon or hydrocarbon molecules, and (c) separating and isolating the planes of hexagonal carbon atoms or fused aromatic rings to recover graphene sheets from the disordered matrix.