Combining semiconductor photocatalysts with carbon nanostructures has been extensively investigated due to their enhanced photochemical conversion activity. While many nanocomposite synthesis methods have been reported, the emerging use of photocatalytic reactions in synthesizing these carbon-based semiconductor composites and even pure carbon nanomaterials is increasingly capturing the attention of the research community. Being categorized under photocatalysis, these carbon-based nanomaterials are designed by either utilizing the conduction band electron or valence band hole of a photocatalyst. This perspective surveys the literature, discusses the principle of the method and highlights the recent progress in the development of this synthetic method. Ongoing challenges and new possible solutions encountered in this research area are outlined.