Two new members of the niobium-substituted polytungstophosphate family based on hexalacunary [H2P2W12O48]12− building blocks

Abstract

Two structurally novel nanoscale clusters [{Nb6(O2)4P2W12O57}2]20− (1) and [{P2W12Nb7O63(H2O)2}4{Nb4O4(OH)6}]30− (2) were synthesized under specific reaction conditions. Cluster 1 displays an unprecedented di-Nb–O–Nb-linked Wells–Dawson dimer, whilst cluster 2 contains the highest nuclearity niobium containing heteropolyoxometalate to date. Furthermore, 31P and 183W NMR spectra indicate that the polyanion 2 remains stable in solution. The photocatalytic activities of the respective salts 1a, 2a and K6[α-P2W18O62]·14H2O for H2 evolution were evaluated. The enhanced photocatalytic activity of 2a may be attributed to the incorporation of Nb into the polyoxotungstate framework.