Pd²⁺-conjugated reduced graphene oxide as a highly efficient visible-light-induced photocatalytic Suzuki-Miyaura coupling

In this work, we investigated Pd²⁺- and Pd⁰-loaded graphene oxide (GO) and reduced graphene oxide (r-GO) as water-soluble, visible-light-responsive photocatalysts for the Suzuki-Miyaura C-C coupling reaction. Nanosheets of r-GO (∼200 nm) were found to be a more desirable substrate than GO nanosheets, since the corresponding catalyst showed higher activities than those of the GO catalysts in both the visible-light-induced and thermal reactions. Furthermore, Pd²⁺-loaded GO and r-GO show higher catalytic activities than those of Pd⁰-loaded GO and r-GO because of the more efficient oxidative addition to Pd²⁺ compared with that to Pd⁰. Systematic studies under dark and light conditions demonstrated the synergic contributions of photoexcited electron transfer and the strong photothermal effect of r-GO. Pd²⁺- and Pd⁰-loaded r-GO show four-times higher photocatalytic activities compared to those of Pd⁰-MoS₂ and Pd⁰-WS₂ catalysts for the Suzuki-Miyaura C-C coupling reaction.