Layered van der Waals (vdW) materials have attracted significant attention due to their materials properties that can enhance diverse applications including next-generation computing, biomedical devices, and energy conversion and storage technologies. This class of materials is typically studied in the two-dimensional (2D) limit by growing them directly on bulk substrates or exfoliating them from parent layered crystals to obtain single or few layers that preserve the original bonding. However, these vdW materials can also function as a platform for obtaining additional phases of matter at the nanoscale. Here, we introduce and review a synthesis paradigm, morphotaxy, where low-dimensional materials are realized by using the shape of an initial nanoscale precursor to template growth or chemical conversion. Using morphotaxy, diverse non-vdW materials such as HfO2 or InF3 can be synthesized in ultrathin form by changing the composition but preserving the shape of the original 2D layered material. Morphotaxy can also enable diverse atomically precise heterojunctions and other exotic structures such as Janus materials. Using this morphotaxial approach, the family of low-dimensional materials can be substantially expanded, thus creating vast possibilities for future fundamental studies and applied technologies.
Keywords: Janus structures; anionic modifications; cationic substitutions; chemical conversion; heterostructures; low-dimensional materials; oxidation; synthesis; two-dimensional materials.