Efficient Photocatalytic Degradation of Imidacloprid by Sulfur Vacancy-Modified Mof808-Edta/S-Zn3in2s6 Z-Scheme Heterojunction: Synergistic Effects of Edta-Mediated Morphological Control and Interfacial In–O Bond

Abstract

The excessive use of imidacloprid has posed a severe threat to human health and ecological stability. In this study, a MOF808-EDTA/S-Zn3In2S6 (MEZ) Z-scheme heterojunction with interfacial In‒O bonds is prepared using heterojunction engineering and morphology control for degrading imidacloprid. The introduction of EDTA ligands onto MOF808 surfaces effectively mitigates excessive nanoparticle aggregation, enabling uniform anchoring of MOF808 nanocrystals at the edges of Zn3In2S6 nanosheets containing sulfur vacancies (S-ZIS). This strategy preserves the porous structure of the S-ZIS component in the MEZ, thereby enhancing light-harvesting efficiency through multiple scattering and absorption pathways. The optimized MEZ exhibits degradation rate constants for imidacloprid that are 5.0, 76, 2.8, and 19 times those of S-ZIS, MOF808, MOF808/S-Zn3In2S6, and MOF808-EDTA, respectively. Theoretical calculations and experimental results confirm that the presence of sulfur vacancies and interfacial In‒O bonds facilitates the efficient separation of photogenerated carriers, enhances the ability to adsorb oxygen molecules, and accelerates the generation of singlet oxygen. This synergistic effect endows MEZ with excellent photocatalytic activity, stability, and reusability. Theoretical calculations and mass spectrometry analysis are utilized to propose that the degradation process of imidacloprid mainly involves hydroxylation, denitration, ring-opening reactions, and dealkylation. This study offers effective measures to regulate the distribution of metal-organic frameworks on the semiconductor surface, providing a theoretical basis for rationally developing Z-scheme photocatalysts to remove emerging pollutants and valuable insights into the fundamental mechanisms of pesticide degradation in environmental remediation.

Keywords: Z-scheme heterojunction, Interfacial chemical bond, Sulfur vacancies, Singlet oxygen, Pesticide degradation, DFT calculation, Metal-organic framework