Synergic coordination of multicomponents for the formation of a {Ni30} cluster substituted polyoxometalate and its in situ assembly

Abstract

Developing a new strategy for the synthesis of high-nuclear transition metal (TM) cluster substituted polyoxometalates (POMs) provides an avenue for new materials with unique functions. Herein, the synergetic coordination strategy of 1,2,4-1H-triazole (Htrz), ethylenediamine (en), and a lacunary POM was applied to construct a high-nuclear Ni cluster substituted POM. As a result, a {Ni₃₀} cluster substituted POM, [Ni(trz)₃]₂@[Ni₃₀(H₂O)₁₆]POM, representing the highest-nuclear Ni cluster containing POM at present, was discovered for the first time as the secondary building unit (SBU) of four in situ assembled frameworks, [Ni₁₁(trz)₁₂(en)₄(H₂O)₂₂]H₄{[Ni(trz)₃(H₂O)₃]₂[Ni₃₀(μ₃-OH)₁₈ (H₂O)₁₆(en)₆(PW₉O₃₄)₆]}·4Htrz·222H₂O (1), [Ni₆(trz)₆(μ₃-OH)(en)(H₂O)₁₀]₂H₈{[Ni(trz)₃ (H₂O)₃]₂[Ni₃₀₊₂(μ₃-OH)₁₈(O)₄(H₂O)₁₆(en)₆(PW₉O₃₄)₆]}·4Htrz·94H₂O (2), [Ni₁₄(trz)₁₂(en)₆(H₂O)₃₆Cl₂]{[Ni(trz)₃(H₂O)₃]₂[Ni₃₀(μ₃-OH)₁₈(H₂O)₁₆(en)₆(PW₉O₃₄)₆]}·solvent (3), and [Ni₃(trz)₃(en)(H₂O)₈]₂{[Ni(en)(H₂O)₂]H₄[Ni₆(μ₃-OH)₃(H₂O)₅(en)₃(PW₉O₃₄)]}₂{[Ni(trz)₃ (H₂O)₃]₂[Ni₃₀(μ₃-OH)₁₈(H₂O)₁₆(en)₆(PW₉O₃₄)₆]}·4Htrz·174H₂O (4), which served as stable heterogeneous catalysts in light driven hydrogen evolution. The {Ni₃₀} cluster in the SBU held abundant water ligands. On one hand, these water ligands promoted the coordinating assembly of the [Ni(trz)₃]₂@[Ni₃₀(H₂O)₁₆]POM by ligand replacement. On the other hand, they further coordinated with Ni²⁺ to expand the Ni cluster to a larger one. It is believed that the work will trigger tremendous interest in the fields of both synthesis chemistry of POM and hydrogen evolution catalysts.