Preparation of Au-Pd Composite Structures and Their Applications in the Degradation of Organic Pollutants

The supramolecular cage CC3, which contains imine bonds, was successfully synthesized via the Schiff base reaction between 1,3,5-triformylbenzene and (R, R)-1,2-cyclohexanediamine. Subsequently, the reduced molecular cage RCC3, featuring secondary amine bonds, is obtained by employing NaBH₄ as a reducing agent. Utilizing RCC3 as a template, ultrasmall palladium nanoclusters (Pd@cage) are prepared through a reverse dual-solvent method. Leveraging the protonation and positive charge characteristics of Pd@cage, a bimetallic Au-Pd composite structure is fabricated via an assembly strategy, thereby forming an interfacial electric field. Upon visible light irradiation, gold nanoparticles (AuNPs) exhibit the localized surface plasmon resonance (LSPR) effect, which generates photogenerated electrons and holes. These photogenerated charge carriers are effectively separated in the interfacial electric field. Specifically, the photogenerated electrons (e⁻) are transferred to the surface of Pd@cage, where they reduce O₂ to superoxide anion (O₂^•−), while the holes (h⁺) combine with water molecules to produce hydroxyl radicals (·OH). Experimental results demonstrate that the degradation efficiency of methylene blue by the Au-Pd composite structures is approximately 1.6 times that of AuNPs and 1.5 times that of Pd@cage. The primary reactive oxygen species responsible for the degradation process is the ·OH. Furthermore, the Au-Pd composite structure demonstrates robust photocatalytic degradation activity in various aqueous solutions and holds significant potential for the degradation of organic pollutants in real wastewater.