title: Polyoxometalate-based cobalt-phosphate molecular catalysts for visible light-driven water oxidation.
abstract: A series of all-inorganic, abundant-metal-based, high-nuclearity cobalt-phosphate (Co-Pi) molecular catalysts [{Co4(OH)3(PO4)}4(SiW9O34)4](32-) (1), [{Co4(OH)3(PO4)}4(GeW9O34)4](32-) (2), [{Co4(OH)3(PO4)}4(PW9O34)4](28-) (3), and [{Co4(OH)3(PO4)}4(AsW9O34)4](28-) (4) were synthesized and shown to be highly effective at photocatalytic water oxidation. The {Co16(PO4)4} cluster contains a Co4O4 cubane which is structurally analogous to the [Mn3CaO4] core of the oxygen-evolving complex (OEC) in photosystem II (PSII). Compounds 1-4 were shown to be the first POM-based Co-Pi-cluster molecular catalysts for visible light-driven water oxidation, thus serving as a functional model of the OEC in PSII. The systematic synthesis of four isostructural analogues allowed for investigating the influence of different heteroatoms in the POM ligands on the photocatalytic activities of these Co-Pi cluster WOCs. Further, the POM-based photocatalysts readily recrystallized from the photocatalytic reaction systems with the polyoxoanion structures unchanged, which together with the laser flash photolysis, dynamic light-scattering, (31)P NMR, UV-vis absorption, POM extraction, and ICP-MS analysis results collectively confirmed that compounds 1-4 maintain their structural integrity under the photocatalytic conditions. This study provides not only a valuable molecular model of the "Co-Pi" catalysts with a well-defined structure but also an unprecedented opportunity to fine-tune high-nuclearity POM clusters for visible light-driven water splitting.
authors.affiliation: Key Laboratory of Polyoxometalate Science of the Ministry of Education, Faculty of Chemistry, Northeast Normal University , Changchun, Jilin 130024, P.R. China.
authors.forename: Xin-Bao
authors.initials: XB
authors.lastname: Han
authors.forename: Zhi-Ming
authors.initials: ZM
authors.lastname: Zhang
authors.forename: Teng
authors.initials: T
authors.lastname: Zhang
authors.forename: Yang-Guang
authors.initials: YG
authors.lastname: Li
authors.forename: Wenbin
authors.initials: W
authors.lastname: Lin
authors.forename: Wansheng
authors.initials: W
authors.lastname: You
authors.forename: Zhong-Min
authors.initials: ZM
authors.lastname: Su
authors.forename: En-Bo
authors.initials: EB
authors.lastname: Wang