An entirely earth‐abundant chromophore‐relay water oxidation catalyst triad system, which is robust and efficient at neutral pH, is presented. The synthesis involves the coordination of a porphyrin derivative to a bridging Fe(CN)5 group, which is then reacted with Co ions to prepare a covalently linked chromophore–Prussian blue analogue assembly. Light‐driven water oxidation studies in the presence of an electron scavenger indicate that the triad is active and it maintains a steady activity for at least three hours. Transient absorption experiments and computational studies reveal that the Fe(CN)5 group is more than a linker as it takes part in electron‐transfer and co‐operates with porphyrin in the charge separation process.

A semiconductor−catalyst hybrid assembly for photocatalytic water oxidation was obtained by preparing CoFe Prussian blue particles on Dion−Jacobson type niobate nanosheets, which produces a p−n junction, as evidenced by the Mott− Schottky plot. The hybrid material with a precious-metal-free cocatalyst exhibits an enhanced photocatalytic activity (89.5 μmol g −1 h −1 ) in the presence of S 2 O 8 2− as the electron scavenger. XPS, infrared, XRD, TEM, and SEM studies performed on both pristine and postcatalytic samples indicate that the hybrid assembly exhibits a proper band energy alignment for the photocatalytic water oxidation process and it is stable throughout a 12 h photocatalytic study.

A CoFe Prussian blue analogue is coupled with brown TiO2 nanoparticles to achieve an earth-abundant photocatalytic water oxidation assembly.

The development of earth‐abundant photocatalytic assemblies has been one of the bottlenecks for the advancement of scalable water splitting cells. In this study, a ZnCr layered double hydroxide and a CoFe Prussian blue analogue are combined to afford an earth‐abundant photocatalytic assembly involving a visible light‐absorbing semiconductor (SC) and a water oxidation catalyst (WOC). Compared to bare ZnCr‐LDH, the SC‐WOC hybrid assembly exhibits a threefold enhancement in photocatalytic activity, which is maintained for 6 h under photocatalytic conditions at pH 7. The band energy diagram was extracted from optical and electrochemical studies to elucidate the origin of the enhanced photocatalytic performance. This study marks a straightforward pathway to develop low‐cost and precious metal‐free assemblies for visible light‐driven water oxidation.

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