Enhanced singlet oxygen generation over bismuth oxychloride via polymerized zinc phthalocyanine sensitization: Synergistic energy and electron transfer.

This study aims to enhance singlet oxygen (1O2) generation in visible-light-driven photocatalytic systems through photosensitizer structural regulation and heterojunction engineering. Polyazene zinc phthalocyanine (ZnPPc) was synthesized and coupled with bismuth oxychloride (BiOCl) to construct a BiOCl/ZnPPc composite photocatalyst with a proposed Z-scheme charge transfer pathway. BiOCl/ZnPPc exhibited excellent photocatalytic degradation performance toward the electron-rich antibiotic chlorotetracycline (CTC), with an apparent degradation rate constant of 0.108 min-1, which was nearly one order of magnitude higher than that of pristine BiOCl (0.011 min-1). Reactive species trapping experiments and EPR analysis confirmed that 1O2 was the dominant reactive species, contributing up to 72% to CTC degradation. Photoelectrochemical measurements, PL/phosphorescence analysis, and DFT calculations further revealed that BiOCl/ZnPPc promotes 1O2 generation through the synergistic contribution of energy transfer and Z-scheme interfacial charge transfer pathways. The porous polymeric structure of ZnPPc alleviates the π-π stacking of monomeric ZnPc and facilitates singlet/triplet exciton generation, thereby enhancing 1O2 production via the energy transfer pathway. Meanwhile, the interfacial electronic coupling, built-in electric field, and charge redistribution between BiOCl and ZnPPc promote charge separation and migration, supporting 1O2 generation through the electron transfer pathway. In addition, BiOCl/ZnPPc showed good environmental adaptability and cycling stability, while degradation pathway identification, and toxicity assessment indicated that CTC was mainly transformed into less toxic intermediates with partial mineralization under the present reaction conditions. This work provides a feasible strategy for constructing photosensitizer-based heterojunction photocatalysts capable of efficient 1O2 generation for antibiotic pollutant degradation.