The contemporary era’s top environmental problems include the lack of energy, recycling of waste resources, and water pollution. Due to the speedy growth of modern industrialization, the utilization of non-renewable sources has increased rapidly, which has caused many serious environmental and energy issues. In photocatalysis, as a proficient candidate, g-C3 N4 (metal-free polymeric photocatalyst) has gained much attention due to its auspicious properties and excellent photocatalytic performance. But, regrettably, the quick recombination of pho-toinduced charge carriers, feeble redox ability, and inadequate visible light absorption are some major drawbacks of g-C3 N4 that hamper its photocatalytic ability. Henceforth, these significant limitations can be solved by incorporating modification strate-gies. Among all modification techniques, the amalgamation of g-C3 N4 with two or more photocatalytic semiconducting materials via heterojunction formation is more advantageous. In this review, we have discussed various modification strategies, including conventional, Z-scheme and S-scheme heterojunctions. S-scheme heterojunction is consideredan efficient and profit-able charge transferal pathway due to the excellent departure and transferal of photoexcited charge carriers with outstanding redox ability. Consequently, the current review is focused on various photocatalytic applications of S-scheme-based g-C3 N4 photocatalysts in pollutant degradation, H2 production, and CO2 reduction.