Recent advancements in molybdenum disulfide (MoS2) and its functional nanostructures for photocatalytic and non-photocatalytic organic transformations

The semiconducting properties of 2H-molybdenum disulfide (MoS2) and the superior electron conductivity of 1T-MoS2 have not been extensively studied for selective organic transformations. An overview of recent progress in solution-processed MoS2 nanosheets is presented in this review, with an emphasis on their synthetic strategies, functionalization, hybridization, properties, and applications. The advantages of MoS2-based nanocatalysts, such as eliminating the pre-sulfiding process and reducing nanoparticle aggregation, enable them to be useful in the petroleum-related chemical industry. MoS2 and its composites are well known catalytic materials for the reactions like nitro to amine reduction, crotonaldehyde hydrogenation, phenanthrene hydrogenation and hydrodeoxygenation reactions. Solvothermally synthesized defect-rich mixed 1T-2H MoS2 nanoflowers have been used for enhanced hydrodesulfurization. Moreover, C–C bond forming reactions like Ullmann reactions and oxidation of sulfides to sulfones. MoS2 and its composites have been investigated for the diversity of reduction, oxidation and C–C bond forming reactions. MoS2-RGO nanocomposites have been effectively used as heterogeneous and recyclable catalytic materials for the highly efficient and selective synthesis of indole alkaloids in an aqueous medium. Apart from thermal catalytic organic transformations, the photocatalytic performance of MoS2 heterojunctions with α-Fe2O3, h-BN or Bi2WO6 have been investigated for photocatalytic CO2 reduction. The interaction of MoS2 layers with Bi2WO6 effectively promotes electron-hole pair separation, followed by the transfer of electrons, thereby promoting the photocatalytic reduction of CO2 to methanol and ethanol under visible light irradiation. Moreover, the photocatalytic performance of NiFe2O4/2D MoS2–Pd p-n heterojunction has been used for Suzuki-Miyaura coupling, and Pd@Cu/MoS2 has been investigated for S-S bond forming reaction. Finally, challenges and opportunities in this research area are discussed.