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Graphite carbon nitride (g‐C3N4), as a non‐metallic photocatalyst, possesses special band structure, excellent stability and unique surface properties, which has become a focus of attention for photocatalytic application. However, pure g‐C3N4 is subject to the limit of visible light response, small specific surface area and rapid recombination of photogenerated carriers, which leads to its low photocatalytic efficiency. Due to the unique electronic structure, various quantum dots (QDs) can be applied to modify g‐C3N4 to improve the photocatalytic activity. Thus, we highlight these QDs modified g‐C3N4‐based composites by emphasizing their synthesis, their physicochemical properties as well as their photocatalytic applications in CO2 reduction, hydrogen production and pollutants degradation in this review. At last, critical summaries and some perspectives on the challenges and directions in this research field are also presented. [ABSTRACT FROM AUTHOR]

S-scheme heterostructure can facilitate the separation of carriers while maintain outstanding redox capacity. A series of ternary Bi 7 O 9 I 3 /g-C 3 N 4 /Bi 3 O 4 Cl photocatalytic system was triumphantly synthesized via oil bath method in this work and used in photocatalytic degradation of phenol. The optimal TOC removal rate reached up to 93.57% under illumination for 160 min, which was slightly lower than phenol photodegradation (about 100%, 100 min). Correspondingly, the apparent rate constants for the decay of phenol are determined to be 0.0211 min−1. The experiment of free radical capture indicated that ·OH and ·O 2 − were the major oxidizing substances to degrade phenol. The products of phenol photodegradation were identified by high performance liquid chromatography (HPLC) and a possible degradation pathway was proposed. The characterization analysis and density functional theory (DFT) calculations demonstrated that dual S-scheme charge migration was generated at the interface of Bi 7 O 9 I 3 , g-C 3 N 4 and Bi 3 O 4 Cl, contributing to an efficient separation of light-excited carriers. In the field of environmental remediation, the discovery of this work could open up promising vistas for designing bismuth-based ternary heterostructures with application potentiality. [Display omitted] • Flower spherical-like Bi 7 O 9 I 3 /g-C 3 N 4 /Bi 3 O 4 Cl was synthesized by oil bath method. • Bi 7 O 9 I 3 /g-C 3 N 4 /Bi 3 O 4 Cl heterojunction with enhanced phenol degradation activity. • ·OH and ·O 2 − were the major oxidizing substances to degrade phenol. • Bi 7 O 9 I 3 /g-C 3 N 4 /Bi 3 O 4 Cl composite followed dual S-scheme heterojunction photocatalytic mechanism. • Dual S-scheme Bi 7 O 9 I 3 /g-C 3 N 4 /Bi 3 O 4 Cl heterojunction contribute to an efficient separation of light-excited carriers. [ABSTRACT FROM AUTHOR]