Post-modification engineering of cerium metal-organic frameworks for efficient visible light-driven water oxidation

Metal-organic frameworks (MOFs) are highly desirable for promising photocatalytic water splitting, but their practical application is greatly limited due to their unstable chemical properties and insufficient visible light response as well as low charge-carries utilization, especially in photocatalytic O₂ production. Herein, we present a post-modification engineering to modulate cerium metal-organic frameworks (Ce-MOFs) for realizing efficient photocatalytic water oxidation to liberate O₂ by visible light. The one-step partial oxidation strategy is adopted to modify pristine Ce-MOFs, yielding the new Ce-MOFs (MV-Ce-MOFs) with mixed valence of Ce³⁺/Ce⁴⁺. Creating the Ce nodes of a mixed valence state can effectively extend the optical absorption to the visible region, expose more catalytically active sites and inhibit the recombination of photoinduced charges. Consequently, the MV-Ce-MOFs exhibit high activity for photocatalytic O₂ evolution under visible light, manifesting an impressive 1.6% apparent quantum efficiency (AQY) under monochromatic irradiation of 405 nm. The regulation engineering of MOF metal node valence heralds a new paradigm for designing MOF-based photocatalysts. Graphical abstract: (Figure presented.)