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

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 (H2) production in both pH = 2 and 12 aqueous solutions using Pt as a cocatalyst (Pt/Ce-TTCA), with H2 production rates of 60.3 and 348.8 mu mol g-1 h-1, respectively. More impressively, partial oxidation of Ce3+ to Ce4+ in Ce-TTCA not only extends the light harvesting ability, but also promotes the effective charge separation, thus greatly improving photocatalytic H2 production activity. The Pt/ Ce-TTCA-65 with the content of 65 % Ce4+ shows 6-fold improvement of photocatalytic activity than that of Pt/ Ce-TTCA without Ce4+, 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.