The development of logical visible-light-driven heterogeneous photosystems for water splitting is a subject of new research. As the first example of a noble-metal-free photocatalyst for both H-2 and O-2 production, a high-nuclear {CuI24(mu 3-Cl)8(mu 4-Cl)6}-based polyoxometalate (POM)@metal-organic framework (MOF) (ZZULI-1) is rationally designed to serve as a robust dual-functionalized photocatalyst. ZZULI-1 exhibits highly efficient photocatalytic H-2 evolution (6614 mu mol g(-1) h(-1)) and O-2 evolution (1032 mu mol g(-1) calculated for the first 6 min). The {CuI24(mu 3-Cl)(8)(mu(4)-Cl)(6)} clusters and mixed POMs not only work as the active units for H-2 and O-2 production, respectively, but also improve the effective electron transfer between the photosensitizer and ZZULI-1. The highly stable dual-functionalized ZZULI-1 affords new penetrations into the development of cost-effective high-nuclear cluster-based POM@MOFs for efficient solar-to-fuel generation.