Selective micropollutant degradation via nanoconfined core-shell heterostructures with robust resilience to water matrices

The increasing presence of emerging organic micropollutants in water systems poses a significant threat to global water security, yet their selective degradation within complex real water matrices remains a critical challenge. Here, we report the rational design of a TiO₂/C₂N core-shell photocatalyst that leverages a type II heterostructure-induced built-in electric field to create nanoconfined catalytic sites on the TiO₂ surface. The C₂N shell selectively allows micropollutants and free chlorine (as an oxidant) to access these catalytic sites while blocking natural organic matter (NOM) via size exclusion and repelling anions through electrostatic interactions, thereby facilitating the selective degradation of micropollutants. The TiO₂/C₂N heterostructures confine 82.7% of hydroxyl radicals (HO^•) near the TiO₂ surface, maintaining nearly 100% micropollutant degradation efficiency across varying NOM and anions concentrations, a wide pH range, and real water samples, while unconfined counterparts suffer a 40%-80% reduction in performance. Moreover, precise control of the C₂N shell thickness at 5-6 nm optimizes light absorption, oxygen diffusion, and HO^• confinement. Additionally, the exclusion of NOM from reaction sites minimizes the formation of toxic disinfection byproducts. This study offers a simple yet viable strategy for developing core-shell photocatalytic heterostructures to selectively degrade target micropollutants in real-world water environments.