Manipulating metal oxidation state over ultrastable metal-organic frameworks for boosting photocatalysis

An exceptionally stable cerium metal-organic framework can achieve photocatalytic H 2 production activity in both pH = 2 and 12 aqueous solutions. More importantly, when the Ce 3+ in Ce-oxo chains was oxidized to Ce 4+ ions by H 2 O 2 , the photocatalytic H 2 production rate has achieved 6-fold improvement, for the first time highlighting the role of metal oxidation state in MOF photocatalysis for H 2 production. • An ultrastable Ce 3+ -based MOF has been prepared. • The Ce 3+ in this MOF can be partly oxidized to Ce 4+ by H 2 O 2 . • The photocatalytic H 2 production activity in this MOF shows 6-fold improvement after Ce 4+ introduction. The development of efficient and stable photocatalysts in drastic conditions is highly desirable yet remains challenging. Herein, we report an exceptionally stable cerium metal-organic framework (MOF), Ce-TTCA, which can achieve photocatalytic hydrogen (H 2 ) production in both pH = 2 and 12 aqueous solutions using Pt as a cocatalyst (Pt/Ce-TTCA), with H 2 production rates of 60.3 and 348.8 μmol g −1 h −1 , respectively. More impressively, partial oxidation of Ce 3+ to Ce 4+ in Ce-TTCA not only extends the light harvesting ability, but also promotes the effective charge separation, thus greatly improving photocatalytic H 2 production activity. The Pt/Ce-TTCA-65 with the content of 65 % Ce 4+ shows 6-fold improvement of photocatalytic activity than that of Pt/Ce-TTCA without Ce 4+ , well highlighting that the crucial role of metal oxidation state in photocatalysis. This work represents the first report on regulating MOF photocatalysis for hydrogen production by manipulating the metal oxidation state.