Carbon-rich carbon nitride for singlet-oxygen-driven photocatalytic degradation of benzophenone-3 and coral vitality recovery.

Coral reefs, vital marine ecosystems, are increasingly threatened by global warming and chemical pollutants such as benzophenone-3 (BP-3), a widely used UV filter. To address this challenge, we present a carbon-doped graphitic carbon nitride (g-C3N4) photocatalyst with efficient singlet oxygen (1O2) generation for BP-3 degradation and coral vitality restoration under simulated seawater conditions. The photocatalyst exhibits improved stability and photocatalytic performance in complex seawater environments, with enhanced charge separation and an approximately eightfold increase in the apparent degradation rate of BP-3 compared with pristine g-C3N4. Toxicity assessments indicate reduced ecological risks of degradation intermediates and significant recovery of zooxanthellae density and coral-algal symbiosis. Immobilized catalyst architectures further minimize material loss and provide a suitable substrate for coral attachment. In this work, we demonstrate a seawater-stable, 1O2-driven photocatalytic strategy that enables efficient BP-3 removal and promotes coral vitality recovery, thereby offering a scalable approach for marine environmental remediation and coral ecosystem restoration.