The use of graphene-based materials as co-catalysts are explored in the production of active filter media for methanol gas-phase photo-oxidation. The present work is intended to show the relationship between the composition and the morphology of the photocatalytic systems with the performance of nanostructured mats. Three different graphene-based co-catalysts have been used (graphene oxide, reduced graphene oxide, and few-layer graphene) and the effect of the different degrees of oxidation has been explored. The comparison of the obtained results has revealed that the structure of the media united with the affinity of the graphene-based co-catalysts with the polymer matrix, strongly affect the photocatalytic efficiency. The reduced graphene oxide has given the best performance, in terms of a higher rate of gas-phase methanol degradation, thanks to the enhanced electron mobility ensured by its deep contact with the photocatalyst itself.