Topological transformation from non-van der Waals solids to 2D transition metal chalcogenides in molten salts with solvated metals

Abstract Transition metal chalcogenides (TMCs) have attracted great attention due to their wide range of applications. The TMCs have been widely synthesized using techniques such as exfoliation and vapor-phase growth, while their structure and constituent tuning remains a challenge. Here, we show a general route to synthesize 2D TMCs by topological transformation of AMX 2 -type ternary metal chalcogenides in molten salts with solvated metals. In this process, the solvated metals in the molten salts play a role of etchant that can remove the A-layer atoms from the AMX 2 structure, resulting in the formation of laminated MX 2 layers. The laminated MX 2 layers provide natural template for cations intercalation or atom substitution to form 2D TMCs with various structures. In the present work, 2D TMCs with tunable stoichiometries (e.g. Cr 2 S 3 , Cr 3 S 4 , Cr 5 S 6 , and Cr 7 S 8 ), as well as 2D TMCs with heterostructures (e.g. Cr 2 S 3 -Ti 0.5 CrS 2 , Cr 2 S 3 -NbS 2 , and Cr 2 S 3 -HfS 2 ) were obtained. We further explored the potential of this route to tail the dielectric properties and improve the electromagnetic wave absorption ability of the chromium sulfides. This approach shows advantage in exploring 2D structures with unprecedented constituent and we believe it will open up opportunities for tuning the properties and broaden the functional applications of TMCs.