Next-generation Ti₃C₂ MXenes quantum dots modified g-C₃N₄ nanosheets photocatalysts for enhanced CO₂ reduction to green fuels and chemicals

The increasing concentration of atmospheric CO₂ caused by rapid industrialization and fossil fuel consumption created an urgent need for sustainable technologies capable of converting CO₂ into valuable fuels and chemicals. Among emerging photocatalytic materials, graphitic carbon nitride (g-C₃N₄) nanosheets (NSs) have emerged as promising metal-free, visible-light-active photocatalysts for CO₂ conversion; however, their practical application is limited by rapid charge recombination and sluggish surface reaction kinetics. In this study, Ti₃C₂ (TC) MXenes quantum dots (MQDs) were integrated with g-C₃N₄ NSs (g-CN NSs) through a self-assembly approach to overcome these limitations. Comprehensive characterization techniques confirmed the successful incorporation of TC-MQDs in g-CN NSs, resulting in improved charge separation and transfer. The photocatalytic CO₂ reduction (PCCO₂R) performance was evaluated in a gas-solid phase photoreactor under visible light irradiation. The optimized 6 wt% TC-MQDs/g-CN NSs photocatalysts achieved significantly enhanced CO and CH₄ production rates of 226.07 µmol g^–1 h^–1 and 48.44 µmol g^–1 h^–1, respectively, representing approximately 29- and 48-fold improvements compared with pristine g-CN NSs. This enhancement is attributed to the dual function of TC-MQDs as efficient electron acceptors that suppress charge recombination and as active sites facilitating CO₂ adsorption and activation. Furthermore, the optimized photocatalyst achieved a total apparent quantum yield (AQY) of 2.45% with CO selectivity of 82.35% and CH₄ selectivity of 17.65%. The composite also exhibited excellent stability during repeated photocatalytic cycles. This work demonstrates the potential of advanced MXenes-based photocatalysts for efficient solar-driven CO₂ conversion and renewable fuel generation, supporting carbon neutrality and sustainable energy technologies.