Carbon nanostructures for photocatalytic degradation of organic pollutants: Synthesis strategies and functionalization techniques

Persistent organic pollutants (POPs) pose a growing environmental and public health crisis, necessitating the development of advanced, sustainable remediation strategies. Carbon nanostructures (CNSs)—including fullerenes, carbon nanotubes (CNTs), graphene, quantum dots (CQDs/GQDs), and nanodiamonds—offer unprecedented photocatalytic potential owing to their tunable dimensionality (0D–3D), high surface area, and exceptional charge transport. This review delivers a mechanistically driven and application-oriented perspective on CNS-based photocatalysts, emphasizing structure–property correlations, targeted surface engineering, and advanced synthesis routes. We highlight how heteroatom doping, defect manipulation, and covalent/non-covalent functionalization modulate band gaps, enhance light harvesting, and accelerate interfacial charge transfer. At the same time, type-II and Z-scheme heterojunction architectures preserve redox potential and minimize recombination. Uniquely, this article integrates green synthesis strategies, computational modeling, machine learning, and toxicity assessments into a unified design roadmap, offering insights beyond conventional literature surveys. Remaining challenges—such as synthesis reproducibility, dispersibility, photostability, and environmental risk—are critically analyzed, with strategic recommendations for scalable, low-cost, and safe CNS deployment. By bridging mechanistic fundamentals with translational pathways, this review positions CNSs as next-generation, high-performance platforms for large-scale photocatalytic water purification and pollutant degradation.