The topological insulator Bi₁₄Rh₃I₉, 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 Bi₁₄Rh₃. The orthorhombic structure of Bi₁₄Rh₃ 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 (Formula presented.) Bi₁₂Rh₃]³⁺ of the precursor Bi₁₄Rh₃I₉ and the (Formula presented.) Bi₁₂Rh₃]²⁺ framework of the product Bi₁₄Rh₃ 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.