Excessive release of greenhouse gas carbon dioxide (CO2) into the atmosphere and continuous utilization of fossil fuels has resulted in global warming and energy shortage. Among the different alternatives, photocatalytic conversion of CO2 to fuels and hydrogen production is a promising approach. To achieve this goal, highly efficient and low-cost semiconductor are demanding to maximize solar energy conversion to renewable fuels. In this perspective, metal free two-dimensional (2D) graphitic carbon nitride (g-C3N4) has attracted numerous considerations because of its low cost and higher reduction potential, but it has a lower efficiency. Herein, we demonstrated various engineering defect strategies in g-C3N4 to promote photocatalytic efficiency under solar energy. Initially, an overview of engineering defects, creation of different vacancies in g-C3N4, and their identification is discussed. In the main stream defect, engineering such as carbon, nitrogen, and oxygen to promote g-C3N4 photocatalytic efficiency is systematically disclosed. Subsequently, the role of sulfur (S) and phosphorus (P) atoms in g-C3N4 to maximize CO2 reduction and hydrogen production are deliberated. The comparative analysis, efficiency enhancement, and role of defect engineering are finally discussed to get higher yields and productivities under solar energy utilization.

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Summary Exfoliated vanadium aluminum carbide (V2AlC) MAX nanosheets coupled with porous graphitic carbon nitride to construct 2D/2D V2AlC MAX/g‐C3N4 heterojunction for photocatalytic CO2 reduction through dry reforming of methane has been investigated. Good interfacial interaction was achieved which enabled proficient charge carrier separation with promoted light absorption. The optimized 10 wt%V2AlC MAX/g‐C3N4 was more proficient with CO and H2 evolution rates of 118.74 and 89.52 μmole g−1 h‐1 at selectivity 57.01 and 42.98%, respectively. This efficiency for CO and H2 evolution rate was 2.21‐ and 1.99‐folds superior to using pure g‐C3N4. This improvement is due to good interfacial contact and efficient charge carrier separation by MAX, which increases photo‐induced charge carrier lifetime. The performance was further investigated with different reforming systems to manipulate the effective utilization of holes to extend charges recombination rate. Using CO2 reduction with hydrogen, CO2 methanation and the reverse water‐gas shift reaction were activated, whereas CO2 with water promoted more methane formation. By investigating CH4/CO2 feed ratios, the highest yield rates attained with the ratio of 1:0, confirming V2AlC based‐composite effectively activates both gases as evidenced by their apparent quantum yields. This study provides a promising route for the fabrication of noble‐metal‐free nanocomposite and will be useful for future energy and environmental applications.