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.