Phase engineering of polyoxometalate assembled superstructures

Superstructures of cluster assemblies have extraordinary properties compared with individual clusters, however, their precise synthesis and phase engineering remain challenging. Here the modular synthesis of a library of clusters based on anisotropic polyoxometalate clusters (CTA)₂(TBA)₂[PW₁₁MO₃₉] (PW₁₁M) is reported. Different phases of superstructures including nanoribbons, spiral nanosheets, tetragonal nanosheets, polyhedral frameworks and nanotubes are prepared by the tuning of interactions between and inside the polyoxometalate building blocks. This synthetic strategy can be applied to six kinds of PW₁₁M cluster building block. A phase diagram based on these results, which can be used to adjustably assemble polyoxometalate clusters, is presented. The direct bonding of clusters and electron delocalization among nanoribbons results in improved conductivity and reduced energy barrier for redox reactions. The nanoribbons exhibit enhanced activity for photoresponse and catalytic olefin epoxidation compared with unassembled clusters. The phase engineering of cluster-assembled superstructures with atomic precision models may help understand the structure–property relationship at the sub-nanometre scale.