Oxygen vacancy-engineered Ti₃C₂Tₓ MXenes for photocatalytic degradation of pharmaceutical residues in aqueous systems: Molecular mechanisms and future directions

The increasing prevalence of pharmaceutical contaminants in aquatic environments poses a critical challenge to water safety and ecological health. Among emerging remediation strategies, Ti₃C₂Tₓ MXenes—two-dimensional transition metal carbides—have garnered attention for their unique tunable surface chemistry and photocatalytic activity. This review provides an in-depth analysis of the role of oxygen vacancy engineering in enhancing the photocatalytic degradation of pharmaceuticals. We explore synthetic strategies for inducing oxygen vacancies, their impact on band structure modulation, charge separation, and reactive oxygen species generation, and how these vacancies facilitate pollutant-specific interactions at the molecular level. Comparative analyses with conventional photocatalysts underscore the superior reactivity, selectivity, and scalability potential of Ti₃C₂Tₓ-based systems. Mechanistic insights, drawn from both experimental studies and density functional theory, reveal critical pathways for pollutant degradation. The review concludes with a roadmap outlining future challenges and opportunities, highlighting the promise of AI-guided design and hybrid material architectures in enabling sustainable, precision-targeted water treatment. • Oxygen vacancies in Ti₃C₂Tₓ MXenes boost light absorption, charge dynamics, and pollutant interactions in water. • Integrated experimental–theoretical studies linking spectroscopy, electronic structure, adsorption, and pollutant degradation. • Defect–pollutant interactions: surface vacancies dictate adsorption orientation, charge transfer, and drug degradation selectivity. • Comparative analysis with TiO₂, ZnO, and MOFs shows Ti₃C₂Tₓ–V_O excels in stability, reusability, and ROS generation. • AI-guided defect engineering and hybrid material design for future molecular-level environmental remediation.