Gas flaring remains a persistent global challenge, leading to substantial energy losses and significant environmental impacts through the emission of greenhouse gases. The valorization of flare gas into synthesis gas (syngas) offers a promising pathway towards sustainable energy recovery; however, conventional thermochemical processes are energy intensive and economically demanding. In this context, photocatalytic methane reforming has emerged as an attractive alternative, enabling syngas production under milder conditions. This review provides a comprehensive analysis of photocatalytic methane reforming for flare gas conversion, with a particular focus on graphitic carbon nitride (g–C 3 N 4 )–based photocatalysts. The fundamentals of flare gas and syngas production technologies are first discussed. Then, the mechanistic aspects, thermodynamic considerations, and mass transfer phenomena are examined. Special emphasis is placed on the optical, electronic and structural properties of g-C 3 N 4 . Recent advances in g-C 3 N 4 synthesis, surface modifications are systematically reviewed, demonstrating their effectiveness in enhancing the photocatalytic activity. The application of engineered g-C 3 N 4 photocatalysts in dry and bi-reforming of methane is critically evaluated, with attention to syngas yield. Finally, this review presents a SWOT analysis to assess the strengths, limitations, opportunities, and threats associated with photocatalytic reforming technologies. This review highlights the significant potential and the remaining challenges of g–C 3 N 4 –based photocatalysts for sustainable flare gas utilization and provides future research directions to facilitate the transition from laboratory-scale studies to practical implementation. Unlike conventional reviews that focus on idealized CH 4 /CO 2 feed systems, this work specifically addresses realistic flare gas valorization, considering multicomponent gas mixtures, impurities (e.g., H 2 S), and process-relevant challenges for practical deployment.
Ikreedeegh et al. (Sun,) studied this question.