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

Abstract 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.