A facile one-pot impregnation–thermal reduction strategy was employed to fabricate sandwich-like graphene–g-C₃N₄ (GCN) nanocomposites using urea and graphene oxide as precursors. The GCN sample exhibited a slight red shift of the absorption band edge attributed to the formation of a C–O–C bond as a covalent cross linker between graphene and g-C₃N₄. The GCN sample demonstrated high visible-light photoactivity towards CO₂ reduction under ambient conditions, exhibiting a 2.3-fold enhancement over pure g-C₃N₄. This was ascribed to the inhibition of electron–hole pair recombination by graphene, which increased the charge transfer.