Reorganization of a Layered Structure into a Framework During Liquid‐Phase Exfoliation

The topological insulator Bi 14 Rh 3 I 9 , a layered salt, is exfoliated through a heterogeneous reaction with n ‐butyllithium and subsequent sonication. Precession‐assisted 3D electron diffraction tomography of a nanodomain of an exfoliated platelet revealed that the material is reduced to the intermetallic superconductor Bi 14 Rh 3 . The orthorhombic structure of Bi 14 Rh 3 is a 3D polyhedra framework of edge‐sharing [RhBi 8/2 ] cubes and square antiprisms that has isolated Bi – anions in its helical channels. The kagome‐type layer Bi 12 Rh 3 ] 3+ of the precursor Bi 14 Rh 3 I 9 and the Bi 12 Rh 3 ] 2+ framework of the product Bi 14 Rh 3 have the same composition, very similar structural motifs and interatomic distances, but differ in the dimensionality of the network. The chemical exfoliation, which is based on a redox leaching reaction, is thus accompanied by a topochemical transformation that involves a massive atomic rearrangement in the intermetallic part of the structure. This unconventional and complex process yields an intermetallic compound that exhibits a 3D crystal structure while manifesting the morphology characteristic of a 2D material.