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 {Ni4O4} cubane cores, K1.5Na26.5[{Ni4(OH)3(PO4)}4(A-PW9O34)4]·62H2O (1), Na28[{Ni4(OH)3(PO4)}4(A-PW9O34)2(B-PW9O34)2]·102H2O (2), and Na28[{Ni4(OH)3(VO4)}4(B-PW9O34)4]·74H2O (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.