Design and Synthesis of Eosin Y‐Sensitized MOF‐on‐MOF Heterojunction Photocatalysts for Enhancing Water Splitting

ABSTRACT Constructing metal‐organic framework (MOF) heterojunctions with effective photocatalytic activity, outstanding stability, and integrated redox centers remains challenging. Herein, a chiral [Cu ^I (IPEA)] 1) and an achiral [Cu ^II (IPEA)]·(H ₂ O) 2) (IPEA = (E)‐3‐[4‐(imidazol‐1‐ylmethyl)phenyl]prop‐2‐enoic acid) were hydrothermally self‐assembled. Notably, [Cu ^II (IPEA)]·(H ₂ O) vertically grew on the surface of [Cu ^I (IPEA)] to form a MOF‐on‐MOF S‐scheme heterojunction [Cu ^I Cu ^II (IPEA)] 3). Structural and interfacial charge transfer analyses (SEM/TEM/XRD/IR, XPS/UPS/KPFM, DFT) confirmed a built‐in electric field at the heterojunction interface, efficiently separating electrons/holes at redox terminals. Furthermore, Eosin Y (EY) chemical adsorption on [Cu ^I Cu ^II (IPEA)] sensitized it for photocatalytic H ₂ evolution, achieving a high efficiency of 4800 µmol·g ⁻¹ ·h ⁻¹ . This work offers new insights for solar energy utilization and dye‐containing wastewater reutilization.