Construction of metal-organic nanostructures and their structural transformations on metal surfaces

Metal-organic nanostructures, composed of organic molecules as building blocks and metal atoms as linkers, exhibit high reversibility and flexibility and open up new vistas for the creation of novel metal-organic nanomaterials and the fabrication of functional molecule-based nanodevices. With the rapid development of emerging surface science and scanning probe microscopy, various metal-organic nanostructures, ranging from zero to two dimensions, have been prepared with atomic precision on well-defined metal surfaces in a bottom-up manner and further visualized at the submolecular (or even atomic) level. In such processes, the metal-organic interactions involved and the synergy and competition of multiple intermolecular interactions have been clearly discriminated as the cause of the diversity and preference of metal-organic nanostructures. Moreover, structural transformations can be controllably directed by subtly tuning such intermolecular interactions. In this perspective, we review recent exciting progress in the construction of metal-organic nanostructures on metal surfaces ranging from zero to two dimensions, which is mainly in terms of the selection of metal types (including sources), in other words, different metal-organic interactions formed. Subsequently, the corresponding structural transformations in response to internal or external conditions are discussed, providing mechanistic insights into precise structural control, e.g., by means of metal/molecule stoichiometric ratios (including through scanning probe microscopy (SPM) manipulations), thermodynamic control, introduction of extrinsic competing counterparts, etc. In addition, some other regulatory factors, such as the functionalization of organic molecules and the choice of substrates and lattices, which also crucially govern the structural transformations, are briefly mentioned in each part. Finally, some potential perspectives for metal-organic nanostructures are evoked.