N-Heterocyclic Carbene Functionalization of 2D Transition Metal Dichalcogenides via a Frustrated Lewis Pair Strategy

Molecular functionalization of 2D transition metal dichalcogenides (TMDs), which unites tailorability of organic molecules and robustness of inorganic solids, is important for tuning their surface properties. While it is common to leverage the electronic effect of organic ligands to functionalize TMDs, the corresponding steric hinderance has remained elusive and underexplored. Herein N-heterocyclic carbene (NHC) functionalization of WS₂ is demonstrated via a frustrated Lewis pair (FLP) route, which exploits both the electronic and steric effect for TMD functionalization. The Lewis base, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), is anchored to the sulfur vacancy sites (Lewis acid) of the WS₂ nanostructures with the hybrid-interface-mediated steric hinderance, mimicking the FLP chemistry and enabling dihydrogen cleavage at room temperature and atmospheric pressure. Solid-state nuclear magnetic resonance (ssNMR) results reveal the local chemical environment of the activated hydrogen species, which can be transferred for room-temperature hydrogenation reactions. The insights are useful for designing weak, non-covalent bonds to modify the 2D surface of TMDs for a broad scope of applications.