Formation of CdS quantum dots on zeolitic imidazolate framework-67 dodecahedrons as S-scheme heterojunctions to enhance charge separation and antibacterial activity

• Exposed Co centres-assisted growth of CdS quantum dots on ZIF-67 dodecahedrons. • ZIF-67 coated with CdS quantum dots yielded improved heterojunction materials. • S-scheme charge transfer pathways within these materials were elucidated. • ZIF-67 doped with ∼40 wt.% CdS displays optimal photocatalytic antibiotic activity. Synthesising a heterojunction structure with a tight interface and sufficient contact area is critical for yielding photogenerated carriers with superior migration efficiencies; however, this remains a significant challenge. Herein, zeolitic imidazolate framework-67 (ZIF-67) was synthesised via four different methods. Using methanol as the medium, the as-prepared ZIF-67 (denoted as ZM) exhibited a uniform morphology and good crystallinity. Subsequently, a well-designed step-scheme (S-scheme) CdS@ZM heterojunction was fabricated via the in-situ coating of CdS quantum dots (QDs) on the ZM dodecahedrons. We utilized the exposed Co centres in the ZM as the “trapping baits” to anchor S 2– precursors and yield a highly dispersed CdS QD coating. Owing to the in-situ coating of CdS QDs, the obtained S-scheme CdS@ZM composites exhibited excellent interfacial contacts and uniform morphological distributions. Under visible light irradiation (λ ≥ 420 nm), the 40%CdS@ZM heterojunctions displayed an excellent photocatalytic sterilisation rate of 97.6% within 15 min in the disinfection of Staphylococcus aureus , which was higher than those of pure ZM (51.0%) and CdS (21.9%). Finally, the S-scheme charge transfer pathway of CdS@ZM was confirmed using X-ray photoelectron spectroscopy, scanning Kelvin probe microscopy, and electron spin resonance analyses.