Tuning redox ability of Zn3In2S6 with surfactant modification for highly efficient and selective photocatalytic C-C coupling

Abstract

Heterogeneous photocatalytic C-C coupling is a green and efficient approach to producing valuable chemicals. The strategies for guiding effective photocatalyst design are desired but still limited. Here, we report visible-light-driven highly selective photocatalytic C-C coupling of benzyl alcohol over surfactant-modified Zn3In2S6 semiconductors. A complete switch of product selectivity from benzyl aldehyde (91.5 %) to C-C coupling products (96.5 %) is obtained by the modification of Zn3In2S6 with stearyl trimethyl ammonium bromide (STAB). This modification assists the formation of sulfur vacancies on Zn3In2S6 to enhance charge carrier separation, thereby increasing the photocatalytic activity. The selectivity switch is mainly attributed to increasing conduction band position of Zn3In2S6 by surfactant modification which strengthens the reduction ability of photogenerated electrons to induce the reversible reduction of benzyl aldehyde to ketyl radicals, and partially to the poor oxidation ability of the material that inhibits the oxidation of ketyl radicals to benzyl aldehyde. Encouragingly, this universal protocol has been successfully applied to a series of aromatic alcohols and biomass-derived furanic alcohols to selectively produce C-C coupling products.