Design and application of two-dimensional organic metal chalcogenides

2D materials exhibit unique physical and chemical properties because of their distinct structures and quantum confinement effects. Characterized by a high surface area, tunable electronic properties, and excellent mechanical strength, these materials are highly attractive for a wide range of applications, including electronics, energy storage, catalysis, sensing, and biomedicine. The modification of inorganic 2D materials with organic functional motifs to optimize their properties is in high demand. Conventional approaches for 2D materials functionalization typically involve harsh chemical processes, including high-temperature treatments and strong acid or base etching. Such harsh conditions can introduce additional defects or result in inhomogeneous functional group distribution. These defects and uneven functionalization can substantially degrade the intrinsic properties of 2D materials, limiting their practical applications.By contrast, organic metal chalcogenides (OMCs) represent an emerging, highly promising class of 2D materials characterized by exceptionally unique layered structures. In these structures, the organic functional moieties are covalently bonded and arranged in a long-range ordered manner outside the inorganic layer, and the adjacent monolayers are connected by weak van der Waals interactions. These weak interactions provide mild exfoliation conditions for OMC bulk precursors, thereby reducing the defects on the surface. Moreover, the inorganic layers and organic functional moieties in OMCs exhibit high design flexibility, providing advantages in terms of structural diversity and functional tunability. The metal centers in OMCs show varied coordination modes and offer various possibilities for the formation of the coordination units, which subsequently assemble into 2D layered structures through diverse linkage patterns. Concurrently, the regularly arranged organic moieties with rich functional diversity serve as chemical gate electrodes that provide extensive opportunities to modulate the electronic structure of OMCs. Thus, OMCs have garnered considerable attention due to their promising applications in optoelectronic detection, gas sensing, energy conversion, catalysis, and other fields. For instance, in optoelectronic detection, OMCs exert exciton effects comparable with those of monolayer transition metal dichalcogenides (TMDs); these effects enable efficient light absorption and emission, making OMCs potential candidates for short-wavelength, polarization-sensitive materials. In gas sensing, the functionalized surface of OMCs can selectively interact with target gas molecules, leading to detectable changes in their electrical or optical properties. In energy conversion, OMCs can act as catalysts or electrodes in devices such as fuel and solar cells, enhancing their efficiency and stability. Given the growing interest in OMCs, a comprehensive review of their structural types, synthetic methodologies, and applications is crucial. Such a review can provide a deep understanding of their rational design, preparation, and functional development. From the perspective of coordination chemistry, this review provides a detailed summary of OMC precursor structures on the basis of the types of inorganic linking units. It outlines various synthetic methods for producing thin or few-layer OMC nanosheets, including solvent-based techniques, interfacial methods, and liquid-phase ultrasound-assisted approaches. Moreover, the applications of the OMCs materials in various fields such as photoluminescence, photoelectric detection, energy conversion, and catalytic sensing are discussed. Building on the above discussions, we delineate the prevailing challenges within the OMCs domain and offer a forward-looking perspective on their developmental trajectory. This trajectory encompasses the precise modulation of layered structure thickness, the orchestrated co-assembly of multi-component OMCs, and the innovative incorporation of novel properties via elemental doping. This review is expected to provide a valuable reference for advancing the development of this burgeoning field at its nascent stage.