Bio-inspired assembly of cubane-adjustable polyoxometalate-based high-nuclear nickel clusters for visible light-driven hydrogen evolution

By artificial mimic of the natural [FeFe]-hydrogenases, a series of polyoxometalate-based high-nuclear Ni clusters containing a varying number of {Ni404} cubane cores, K1.5Na26.5 [{Ni-4(OH)(3)(PO4)}(4)(A-PW9O34)(4)]center dot 62H(2)O (1), Na-28 [{Ni-4(OH)(3)(PO4)(4)(A-PW9O34)(2) (B-PW9O34)(2)center dot 102H(2)O (2), and Na-28[{Ni-4(OH)(3) (VO4)}(4)(B-PW9O34)(4)74H(2)O (3), were synthesized and systematically characterized. Compounds 1_3 contain {Ni16(XO4)(4)(OH)(12) (X = P, V) core encapsulated by the trivacant A-/B-{PW9O34} ligands. Compounds 1-3 as homogeneous catalysts for visible-light-driven H2 evolution indicate that they not only show high photocatalytic performance (High TON of 578.8, 679.1, and 931.1 for 1-3 were achieved, respectively), but also their catalytic performance was improved with the increasing number of {Ni4O4} cubanes. Multiple stability experiments confirm that compounds 1-3 maintain their structure intact under the photocatalytic conditions. The above research provides a platform for mimicking the structures of natural hydrogenases to further explore more efficient and inexpensive H2 evolution catalysts. (C) 2017 Published by Elsevier B.V.