Site-Selective Surface Modification of 2D Superatomic ReSe.

Coating two-dimensional (2D) materials with molecules bearing tunable properties imparts their surfaces with functionalities for applications in sensing, nanoelectronics, nanofabrication, and electrochemistry. Here, we report a method for the site-selective surface functionalization of 2D superatomic ReSeCl monolayers. First, we activate bulk layered ReSeCl by intercalating lithium and then exfoliate the intercalation compound LiReSeCl in -methylformamide (NMF). Heating the resulting solution eliminates LiCl to produce monolayer ReSe(NMF) ( ≈ 0.4) as high-quality nanosheets. The unpaired electrons on each cluster in ReSe(NMF) enable covalent surface functionalization through radical-based chemistry. We demonstrate this to produce four previously unknown surface-functionalized 2D superatomic materials: ReSeI, ReSe(SPh), ReSe(SPhNH), and ReSe(SCH). Transmission electron microscopy, chemical analysis, and vibrational spectroscopy reveal that the in-plane structure of the 2D ReSe material is preserved through surface functionalization. We find that the incoming groups control the density of vacancy defects and the solubility of the 2D material. This approach will find utility in installing a broad array of chemical functionalities on the surface of 2D superatomic materials as a means to systematically tune their physical properties, chemical reactivity, and solution processability.