Synergetic Relay of Oxygen Transfer and Benzene-Ring-Opening Processes for Efficient Dechlorination Reactions.

The efficient dechlorination of persistent chlorinated aromatic pollutants remains a significant challenge as conventional single-process advanced reduction processes (ARPs) often suffer from low efficiency and fail to achieve ring-opening degradation. Herein, we report a synergistic nonradical relay system involving high-valent cobalt-oxo species (HVCO) and singlet oxygen (1O2) for the effective degradation of recalcitrant chlorinated aromatic contaminants. This system is enabled by a novel TiO2@Co3O4 core-shell Z-scheme heterojunction photocatalyst (TCZ). Under solar-light irradiation, TCZ achieves efficient separation of photogenerated charge carriers via a Z-scheme mechanism while preserving strong redox potentials. The photoinduced electrons are transferred to peroxymonosulfate (PMS) at the Co3O4 shell, which acts as an effective activator to generate HVCO through oxygen-transfer-driven dechlorination. Simultaneously, the holes oxidize PMS to produce 1O2, leading to benzene-ring-opening. The TCZ/PMS/solar system demonstrated outstanding performance in the dechlorination and oxidation of 4-chlorophenol (4-CP) and ring-opening degradation of Rhodamine B (RhB) as model pollutants. The system achieved >98% dechlorination efficiency and complete removal (100%) with rate constants of 0.024 and 0.53 min-1, respectively─significantly surpassing the performance of its individual components. Moreover, the system exhibited excellent stability and long-term activity in a self-designed photofilter reactor, underscoring its practical potential. This work introduces a novel paradigm of "oxygen-transfer-dechlorination/ring-opening-oxidation relay" for complete defunctionalization of refractory organochlorines and opens new avenues for designing cascade systems to treat complex wastewater.