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Photocatalytic reduction of CO₂ with CH₄ through the dry reforming of methane (DRM) is an attractive approach to recycling greenhouse gases into valuable chemicals and fuels; however, this process is quite challenging. Although there is growing interest in designing efficient photocatalysts, they are less stable, and have lower photoactivity when employed for DRM reactions. Herein, we developed a noble metal-free hierarchical graphitic carbon nitride (HC₃N₄) loaded with cobalt (Co) for highly efficient and stable photocatalytic dry reforming of methane to produce synthesis gases (CO and H₂). The performance of the newly designed Co/HC₃N₄ composite was tested for different reforming systems such as the dry reforming of methane, bi-reforming of methane (BRM) and reforming of CO₂ with methanol–water. The performance of HC₃N₄ was much higher compared to bulk g-C₃N₄, whereas Co/HC₃N₄ was found to be promising for higher charge carrier separation and visible light absorption. The yield of CO and H₂ with HC₃N₄ was 1.85- and 1.81-fold higher than when using g-C₃N₄ due to higher charge carrier separation. The optimized 2% Co/HC₃N₄ produces CO and H₂ at an evolution rate of 555 and 41.2 µmol g⁻¹ h⁻¹, which was 18.28- and 1.74-fold more than using HC₃N₄ during photocatalytic dry reforming of methane (DRM), with a CH₄/CO₂ feed ratio of 1.0. This significantly enhanced photocatalytic CO and H₂ evolution during DRM was due to efficient charge carrier separation in the presence of Co. The CH₄/CO₂ feed ratio was further investigated, and a 2:1 ratio was best for CO production. In contrast, the highest H₂ was produced with a 1:1 feed ratio due to the competitive adsorption of the reactants over the catalyst surface. The performance of the composite was further investigated for bi-reforming methane and methanol. Using photocatalytic CO₂ reduction with CH₄/H₂O, the production of CO and H₂ was reduced, whereas significantly higher CO and H₂ evolved using the BRM process involving methanol. Using methanol with CO₂ and H₂O, 10.77- and 1.39-fold more H₂ and CO efficiency was achieved than when using dry reforming of methane. The composite was also very stable for continuous synthesis gas production during DRM in consecutive cycles. Thus, a co-assisted g-C₃N₄ nanotexture is promising for promoting photocatalytic activity and can be further explored in other solar energy applications.