Two-Dimensional MoS2 Catalyzed Oxidation of Organic Thiols

Abstract

Thiol-chemistry directed techniques have been extensively employed to modify the properties of two-dimensional MoS2 nanosheets, aiming to heal or functionalize sulfur vacancies. However, the exact nature of the organic thiol/exfoliated MoS2 interaction remains under dispute. Herein, the reactions between 2H-MoS2 and organic thiols are explored in detail. We quantitatively monitor the consumption of 1-octanethiol in the presence of exfoliated 2H-MoS2 nanosheets using 1H nuclear magnetic resonance spectroscopy. The generation of dioctyl-disulfide product was detected as the only product of the 2H-MoS2/1-octanethiol reaction. Furthermore, it was found that this reaction was catalytic, and was not caused by atmospheric dioxygen. In addition, we found that the following affected the kinetics of the reaction: the thickness of the exfoliated 2H-MoS2 nanosheets, the use of deuterated substrate (kinetic isotope effect = 2), and the electron donating nature of the thiol substrate. The disulfide product was postulated to be formed via the intermolecular exchange between free thiols and either adsorbed thiolate (or thiyl radicals) or desorbed thiyl radicals. Our studies demonstrate that the “functionalization” of 2H-MoS2 nanosheets with organic thiols is likely simply 2H-MoS2 catalyzed oxidation of the thiol, with no evidence for any bond-forming (covalent or dative) interaction between the thiols and MoS2.