Abstract: The photoreduction of CO₂ using solar energy to produce energy-efficient fuels is a sustainable technology that addresses energy needs while reducing carbon emissions. However, synthesizing efficient and robust photocatalysts for this process is challenging. This study introduces a viable approach for highly selective CO₂ photoreduction to CH₄ production by integrating defect-enriched BiOIO₃ (DEBI) with a Ti₃C₂ (TC) MXene co-catalyst, forming an efficient 2D/2D Schottky-type heterostructure. The DEBI, enhanced with precise defect engineering, showed improved light absorption and charge separation efficiency. In tandem, the TC MXene co-catalyst facilitated rapid electron transfer and significantly minimized charge recombination. Consequently, the DEBI/TC-2 heterostructure, with an optimal 2 wt% TC MXene loading, achieved a CH₄ yield of 52.8 μmol h^-1 g^-1, representing a remarkable 20.5- and 6.3-fold increase over pristine BiOIO₃ and DEBI, respectively. The Schottky-type 2D/2D heterostructure also demonstrated an impressive apparent quantum yield of 0.72%, 99% CH₄ selectivity over H₂ generation, and remarkable stability across multiple cycles. This study underscores the synergistic advantages of defect engineering and MXene co-catalyst integration in a single system, proposing a novel direction for designing highly efficient photocatalysts for solar-driven CO₂ reduction in energy-efficient fuel production.

Key words: BiOIO₃, Ti₃C₂ MXene, Defect engineering, Hybrid heterostructure, Selective CO₂ reduction