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 {Ni 4 O 4 } cubane cores, K 1.5 Na 26.5 [{Ni 4 (OH) 3 (PO 4 )} 4 ( A- PW 9 O 34 ) 4 ]·62H 2 O ( 1 ), Na 28 [{Ni 4 (OH) 3 (PO 4 )} 4 ( A- PW 9 O 34 ) 2 ( B- PW 9 O 34 ) 2 ]·102H 2 O ( 2 ), and Na 28 [{Ni 4 (OH) 3 (VO 4 )} 4 ( B- PW 9 O 34 ) 4 ]·74H 2 O ( 3 ), were synthesized and systematically characterized. Compounds 1 − 3 contain {Ni 16 (XO 4 ) 4 (OH) 12 } (X = P, V) core encapsulated by the trivacant A- / B- {PW 9 O 34 } ligands. Compounds 1 − 3 as homogeneous catalysts for visible-light-driven H 2 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 {Ni 4 O 4 } 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 H 2 evolution catalysts.