Visible-Light-Driven Selective Hydrogenation of Nitrostyrene over Layered Ternary Sulfide Nanostructures.

Abstract

Selective hydrogenation of nitrostyrenes is a great challenge due to the competitive activation of the nitro groups (─NO2 ) and carbon-carbon (C═C) double bonds. Photocatalysis has emerged as an alternative to thermocatalysis for the selective hydrogenation reaction, bypassing the precious metal costs and harsh conditions. Herein, two crystalline phases of layered ternary sulfide Cu2 WS4 , that is, body-centered tetragonal I-Cu2 WS4 nanosheets and primitive tetragonal P-Cu2 WS4 nanoflowers, are controlled synthesized by adjusting the capping agents. Remarkably, these nanostructures show visible-light-driven photocatalytic performance for selective hydrogenation of 3-nitrostyrene under mild conditions. In detail, the I-Cu2 WS4 nanosheets show excellent conversion of 3-nitrostyrene (99.9%) and high selectivity for 3-vinylaniline (98.7%) with the assistance of Na2 S as a hole scavenger. They also can achieve good hydrogenation selectivity to 3-ethylnitrobenzene (88.5%) with conversion as high as 96.3% by using N2 H4 as a proton source. Mechanism studies reveal that the photogenerated electrons and in situ generated protons from water participate in the former hydrogenation pathway, while the latter requires the photogenerated holes and in situ generated reactive oxygen species to activate the N2 H4 to form cis-N2 H2 for further reduction. The present work expands the rational synthesis of ternary sulfide nanostructures and their potential application for solar-energy-driven organic transformations.