Boosted Heterogeneous Catalysis by Surface-Accumulated Excess Electrons of Non-Oxidized Bare Copper Nanoparticles on Electride Support.

Engineering active sites of metal nanoparticle-based heterogeneous catalysts is one of the most prerequisite approaches for the efficient production of chemicals, but the limited active sites and undesired oxidation on the metal nanoparticles still remain as key challenges. Here, it is reported that the negatively charged surface of copper nanoparticles on the 2D [Ca2 N]+ ∙e- electride provides the unrestricted active sites for catalytic selective sulfenylation of indoles and azaindoles with diaryl disulfides. Substantial electron transfer from the electride support to copper nanoparticles via electronic metal-support interactions results in the accumulation of excess electrons at the surface of copper nanoparticles. Moreover, the surface-accumulated excess electrons prohibit the oxidation of copper nanoparticle, thereby maintaining the metallic surface in a negatively charged state and activating both (aza)indoles and disulfides under mild conditions in the absence of any further additives. This study defines the role of excess electrons on the nanoparticle-based heterogeneous catalyst that can be rationalized in versatile systems.

Understanding and Improving Photocatalytic Activity of Pd-Loaded BiVO4 Microspheres: Application to Visible Light-Induced Suzuki-Miyaura Coupling Reaction.

The effective utilization of visible light is required for exploiting photocatalytic reactions in indoor and outdoor environments. In this study, Pd-supported BiVO4 microspheres (Pd-BiVO4) were prepared for visible light-induced photocatalytic reactions. Under irradiation with a white light-emitting diode, the obtained Pd-BiVO4 composite exhibited considerably improved catalytic activity for the decomposition of an organic dye compared with other BiVO4 catalysts. The Pd-BiVO4 composite was also effective for catalytic organic transformation via the visible light-induced Suzuki-Miyaura coupling reaction. The photogenerated electrons in the conduction band of BiVO4 flowed to the Pd nanoparticles and amplified cross-coupling reaction. The influence of the crystal structure and grain size of BiVO4 and the role of the deposited Pd nanoparticles were fully investigated to elucidate the visible light activity of the catalyst. This system highlights the possibility of an indoor light source with low energy density for sustainable organic transformations.

Benzothiazole Synthesis: Mechanistic Investigation of an In Situ-Generated Photosensitizing Disulfide.

The use of a visible light absorbing intermediate as a photosensitizer makes a chemical process simple and sustainable, obviating the need for the use of chemical additives. Herein, the formation of a photosensitizing disulfide in benzothiazole synthesis from 2-aminothiophenol and aldehydes was proposed and confirmed through in-depth mechanistic studies. A series of photophysical and electrochemical investigations revealed that an in situ-generated disulfide photosensitizes molecular oxygen to generate the key oxidants, singlet oxygen and superoxide anion, for the dehydrogenation step.

Facile Synthesis of BiVO4 for Visible-Light-Induced C-C Bond Cleavage of Alkenes to Generate Carbonyls.

BiVO4 crystals synthesized by an ultrasonic-assisted method (Sono-BiVO4 ) showed improved efficiency as a heterogeneous photocatalyst under visible-light irradiation. Sono-BiVO4 was successfully used for the C-C bond cleavage of alkenes to generate carbonyl compounds. Styrene derivatives were converted into carbonyl compounds in the presence of Sono-BiVO4 under highly sustainable conditions requiring only natural sources, that is, molecular oxygen, visible light, and water at room temperature. Additionally, Sono-BiVO4 could be easily separated from the reaction mixture and reused.

Synthesis of fluoroalkylated alkynes via visible-light photocatalysis.

Fluoroalkylated alkynes, which are versatile building blocks for the synthesis of various biologically active organofluorine compounds, were synthesized from easily available alkynyl halides and fluoroalkyl halides by visible-light photocatalysis. Addition of fluoroalkyl radicals to alkynes and subsequent dehalogenation selectively yielded fluoroalkylated alkynes.