Mild Covalent Functionalization of Transition Metal Dichalcogenides with Maleimides: A "Click" Reaction for 2H-MoS2 and WS2

The physical properties of ultrathin transition metal dichalcogenides (2D-TMDCs) make them promising candidates as active nanomaterials for catalysis, optoelectronics, and biomedical applications. Chemical modification of TMDCs is expected to be key in modifying/adding new functions that will help make such promise a reality. We present a mild method for the modification of the basal planes of 2H-MoS2 and WS2. We exploit the soft nucleophilicity of sulfur to react it with maleimide derivatives, achieving covalent functionalization of 2H-TMDCs under very mild conditions. Extensive characterization proves that the reaction occurs through Michael addition. The orthogonality and versatility of the thiol-ene "click" chemistry is expected to allow the a la carte chemical manipulation of TMDCs.