CuO Nanoparticle-Decorated TiO2-Nanotube Heterojunctions for Direct Synthesis of Methyl Formate via Photo-Oxidation of Methanol

Methyl formate is widely employed as one of the important organic intermediates in C1 chemistry and as an environmentally benign chemical in the emerging area of "green chemistry". We here study the catalytic effectiveness of CuO/TiO2-nanotube nanocomposites for the direct synthesis of methyl formate via methanol photo-oxidation in this paper. The CuO/TiO2-nanotube nanocomposites with 7% CuO weight loading give a promising photocatalytic performance (over 93.3% methanol conversion and 89.4% methyl formate selectivity) at 25 °C under 365 nm UV irradiation. The turnover frequency and the apparent quantum efficiency reach up to 22.9 molmethanol gcat -1 h-1 and 57.6% over 7% CuO/TiO2-nanotube, respectively, which is mainly because of the effective minimization of the recombination of photogenerated electrons and holes by the surface ultrasmall-sized CuO particles. Furthermore, these CuO/TiO2-nanotube nanocomposites exhibit excellent durability and robust nature during the catalytic processes of the methanol photo-oxidation to methyl formate. The experimental results demonstrate the promise of the robust CuO/TiO2 nanocomposites for efficient and green production of methyl formate, which may offer guidelines for the design of efficient catalysts for selective alcohol conversion to other valuable chemicals.

Highly Selective Oxidation of Ethyl Lactate to Ethyl Pyruvate Catalyzed by Mesoporous Vanadia-Titania

The direct oxidative dehydrogenation of lactates with molecular oxygen is a “greener” alternative for producing pyruvates. Here we report a one-pot synthesis of mesoporous vanadia–titania (VTN), acting as highly efficient and recyclable catalysts for the conversion of ethyl lactate to ethyl pyruvate. These VTN materials feature high surface areas, large pore volumes, and high densities of isolated vanadium species, which can expose the active sites and facilitate the mass transport. In comparison to homogeneous vanadium complexes and VO_x/TiO₂ prepared by impregnation, the meso-VTN catalysts showed superior activity, selectivity, and stability in the aerobic oxidation of ethyl lactate to ethyl pyruvate. We also studied the effect of various vanadium precursors, which revealed that the vanadium-induced phase transition of meso-VTN from anatase to rutile depends strongly on the vanadium precursor. NH₄VO₃ was found to be the optimal vanadium precursor, forming more monomeric vanadium species. V⁴⁺ as the major valence state was incorporated into the lattice of the NH₄VO₃-derived VTN material, yielding more V⁴⁺–O–Ti bonds in the anatase-dominant structure. In situ DRIFT spectroscopy and density functional theory calculations show that V⁴⁺–O–Ti bonds are responsible for the dissociation of ethyl lactate over VTN catalysts and for further activation of the deprotonation of β-hydrogen. Molecular oxygen can replenish the surface oxygen to regenerate the V⁴⁺–O–Ti bonds.

Understanding the oxidative dehydrogenation of ethyl lactate to ethyl pyruvate over vanadia/titania

We studied the vapour-phase oxidative dehydrogenation of ethyl lactate to ethyl pyruvate over V₂O₅/TiO₂ catalysts in a fixed-bed reactor.

Fabrication of plasmonic Au-Pd alloy nanoparticles for photocatalytic Suzuki-Miyaura reactions under ambient conditions

The Suzuki-Miyaura reaction is one of the most popular and efficient routes for the formation of carbon-carbon bonds in both laboratorial and industrial synthetic processes. Here, we report for the first time that a Au-Pd/TiO₂ catalyst could be utilized efficiently for Suzuki-Miyaura reactions at ambient conditions under visible light with high activity and reusability. Mechanistic investigation by means of experimental methods revealed that through the strong local surface plasma resonance of Au under the visible light, the hot electrons of Au could be injected into Pd in the bimetallic nanoparticles, thus facilitating activation of the aryl halides. Meanwhile, the electropositive Au tended to gain electrons from TiO₂, resulting in the separation of the photogenerated electron/hole pairs of TiO₂, which enabled the holes to activate aryl boronic acids. This Au-Pd/TiO₂ catalyst not only expands the application scope of Suzuki-Miyaura reactions under mild conditions but will also inspire further exploitation of the direct harvesting of visible light by nanomaterials for a wide range of chemical reactions.

Enhanced photoelectronic properties of single crystal TiO2 nanosheet array films by selective deposition of CdS nanoparticles on their {101} facets

The selective deposition of CdS nanoparticles on the {101} facets of TiO₂ enhances the spatial separation of electrons and holes on different facets, thereby improving their photoelectronic properties.