Synergistic effect of electron-rich alkyl-substituted subphthalocyanine H12SubPc-Oph-tBu and cobalt-doping for enhanced photocatalytic performance

Constructing S-scheme heterojunctions serves as a potent approach to boost photocatalytic efficiency by promoting charge transfer and attaining elevated redox potentials. Herein, a novel axially substituted subphthalocyanine derivative, H₁₂SubPc-Oph-tBu (SubPc-tBu), was synthesized and assembled onto cobalt-doped ZnS (Co-ZnS) via supramolecular self-assembly to form a unique S-scheme heterojunction (SubPc-tBu/Co-ZnS). In this system, the electron-rich SubPc-tBu unit, in conjunction with the incorporated cobalt (Co), is pivotal in promoting charge transfer and enhancing the photocatalytic efficiency of the heterojunction. The photocatalyst achieved a 97 % degradation efficiency of furantoin (FT) within 30 minutes, with an apparent rate constant that is 17.24 times higher than ZnS and 10.35 times greater than SubPc-tBu, demonstrating its superior photocatalytic performance. Furthermore, after five consecutive cycles, it retained a degradation efficiency of 83.36 %, highlighting its excellent stability and recyclability. Experimental and theoretical studies revealed that the enhanced photocatalytic activity arises from an interfacial charge transfer mechanism improving carrier separation and transfer. Time-dependent density functional theory (TDDFT) and LC-MS coupled with DFT elucidated electron transfer pathways and pollutant degradation mechanisms, offering insights into photocatalyst design for environmental pollution solutions.