Halide perovskites such as CsPbBr3 and oxide perovskites like SrTiO3 have emerged as promising materials for photocatalytic degradation of persistent organic pollutants, including per- and polyfluoroalkyl substances (PFAS) and endocrine-disrupting compounds (EDCs). Their unique electronic and optical properties, coupled with their ability to generate reactive oxygen species under light irradiation, make them effective in breaking down these hazardous contaminants. However, challenges such as aqueous instability, lead toxicity risks, and long-term durability must be addressed to enable their practical application in water treatment systems.

One of the most significant advantages of halide perovskites is their tunable bandgap, which allows optimization of light absorption across a broad spectrum. CsPbBr3, for example, exhibits a bandgap of approximately 2.3 eV, making it responsive to visible light. This property is crucial for solar-driven photocatalysis, as it maximizes the utilization of natural sunlight. Oxide perovskites like SrTiO3, with a bandgap around 3.2 eV, are more suited for UV light activation but can be modified through doping or defect engineering to extend their absorption into the visible range. The high carrier mobility in these materials further enhances charge separation and reduces recombination losses, leading to more efficient generation of radicals such as hydroxyl (•OH) and superoxide (•O2−), which are critical for pollutant degradation.

Despite their photocatalytic efficiency, halide perovskites face stability issues in aqueous environments. CsPbBr3 undergoes rapid degradation due to the dissolution of lead and halide ions, particularly in the presence of water and oxygen. This not only reduces photocatalytic performance but also raises concerns about secondary contamination from lead leakage. Oxide perovskites like SrTiO3 are more chemically stable in water but may still suffer from surface passivation or reduced activity over prolonged use. To mitigate these issues, encapsulation strategies have been developed. Coating halide perovskites with hydrophobic polymers, silica layers, or carbon matrices can significantly improve their water resistance while maintaining photocatalytic activity. Core-shell structures, where the perovskite is protected by a stable oxide or polymer shell, have also shown promise in preventing lead leakage and enhancing recyclability.

Lead toxicity remains a critical concern for halide perovskites, necessitating stringent encapsulation or the exploration of less toxic alternatives. Partial substitution of lead with tin or bismuth has been investigated, though these variants often exhibit lower stability or reduced photocatalytic efficiency. An alternative approach involves immobilizing perovskite nanoparticles within porous substrates such as alumina or zeolites, which physically restrict lead leaching while providing high surface area for pollutant adsorption and degradation. For oxide perovskites, lead-free compositions are inherently safer, though their catalytic performance must be carefully optimized to match that of lead-based counterparts.

The photocatalytic mechanisms of perovskites for PFAS and EDC degradation involve multiple pathways. PFAS, known for their strong carbon-fluorine bonds, are typically degraded through reductive defluorination or advanced oxidation processes. Halide perovskites have demonstrated effectiveness in breaking down perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) under visible light, with defluorination rates influenced by the material’s band structure and surface chemistry. Oxide perovskites like SrTiO3, when doped with nitrogen or transition metals, exhibit enhanced oxidation capabilities, enabling the breakdown of phenolic EDCs such as bisphenol A (BPA) and 17α-ethinylestradiol (EE2). The generation of reactive species at the perovskite surface facilitates the stepwise cleavage of organic pollutants into smaller, less harmful intermediates, eventually leading to mineralization.

Scalability and practical implementation remain key challenges. While lab-scale studies have demonstrated high degradation efficiencies for specific pollutants, real-world water matrices contain complex mixtures of organics, inorganics, and natural organic matter that can interfere with photocatalytic processes. Fouling of perovskite surfaces by organic residues or precipitation of metal oxides can reduce activity over time. Periodic regeneration techniques, such as thermal treatment or chemical washing, may be required to maintain performance in continuous-flow systems. Additionally, the cost of perovskite synthesis and encapsulation must be balanced against the benefits of their high activity compared to conventional photocatalysts like TiO2.

Future research directions include the development of perovskite-based heterostructures to enhance charge separation and light absorption. Combining halide perovskites with oxide perovskites or metal sulfides could create Z-scheme systems that extend the range of utilizable light while minimizing recombination losses. Advances in computational modeling can aid in predicting optimal compositions and structures for targeting specific pollutants. Furthermore, life-cycle assessments are needed to evaluate the environmental impact of large-scale perovskite deployment in water treatment, ensuring that solutions do not introduce new risks while addressing existing contamination.

In summary, halide and oxide perovskites offer compelling advantages for the photocatalytic degradation of PFAS and EDCs, including tunable bandgaps, high carrier mobility, and efficient radical generation. However, their practical application hinges on overcoming stability limitations, lead toxicity concerns, and scalability challenges. Encapsulation strategies, alternative compositions, and hybrid material designs present viable pathways to harness their potential while mitigating risks. As research progresses, these materials may play a pivotal role in addressing some of the most persistent and hazardous water contaminants.