Self-Assembly of Polyoxometalate-Based Sub-1 nm Polyhedral Building Blocks into Rhombic Dodecahedral Superstructures

Self-assembly of subnanometer (sub-1 nm) scale polyhedral building blocks can yield some superstructures with novel and interesting morphology as well as potential functionalities. However, achieving the self-assembly of sub-1 nm polyhedral building blocks is still a great challenge. Herein, through encapsulating the titanium-substituted polyoxometalate (POM, K7PTi2W10O40) with tetrabutylammonium cations (TBA+), we first synthesized a sub-1 nm rhombic dodecahedral building block by further tailoring the spatial distribution of TBA+ on the POM. Molecular dynamics (MD) simulations demonstrated the eight TBA+ cations interacted with the POM cluster and formed the sub-1 nm rhombic dodecahedron. As a result of anisotropy, the sub-1 nm building blocks have self-assembled into rhombic dodecahedral POM (RD-POM) assemblies at the microscale. Benefiting from the regular structure, Br- ions, and abundant active sites, the obtained RD-POM assemblies exhibit excellent catalytic performance in the cycloaddition of CO2 with epoxides without co-catalysts. This work provides a promising approach to tailor the symmetry and structure of sub-1 nm building blocks by tuning the spatial distribution of ligands, which may shed light on the fabrication of superstructures with novel properties by self-assembly. Tailoring the spatial distribution of ligands on polyoxometalates has led to subnanometer rhombic dodecahedral building blocks being obtained. The anisotropy of these sub-1 nm building blocks results in them self-assembling into rhombic dodecahedral assemblies, which exhibit excellent catalytic performance in the cycloaddition of CO2 with epoxides.image

Automated summary

Tailoring the spatial distribution of ligands on polyoxometalates has led to the formation of subnanometer rhombic dodecahedral building blocks, which self-assemble into microscale rhombic dodecahedral POM assemblies. These assemblies exhibit excellent catalytic performance in the cycloaddition of CO2 with epoxides.