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An unprecedented visible-light-driven photocatalytic system consisting of Pd nanoparticles stabilized on g-C3N4-imine-functionalized TiO2 nanoparticles was discovered for photoassisted hydrogen generation followed by olefin hydrogenation under mild conditions. The structural integrity of the as-synthesized photocatalyst was corroborated by Fourier transform infrared spectroscopy, X-ray powder diffraction, energy-dispersive X-ray spectroscopy, inductively coupled plasma atomic emission spectroscopy, X-ray photoelectron spectroscopy, ultraviolet-diffuse reflectance spectroscopy, Brunauer-Emmett-Teller measurements, and thermogravimetric analysis (TGA). Transmission electron microscopy and high-resolution scanning electron microscopy revealed the nanoscopic nature of the catalyst. The photocatalyst promoted several different transformations in a one-pot reaction sequence: hydrogen evolution through photocatalytic acceptorless formation of benzimidazoles as important therapeutic agents followed by visible-light-driven photocatalytic reduction of olefins with a high hydrogen utilization efficiency of up to 92% under mild conditions. A significant volume of H2 was produced under blue light-emitting diode (LED) irradiation during the selective formation of benzimidazole, while the selectivity reduced significantly under a Xe lamp or in the dark. The in situ-generated H2 could be activated by the as-prepared Pd-C3N4-imine/TiO2 photocatalyst to effectively hydrogenate olefins under mild conditions at appropriate time exposed to blue LED irradiation. The light-dependent photocatalytic performance of the title catalyst was assessed using action spectra by calculating the apparent quantum efficiency (AQE), which exhibited the maximum AQEs at 410 and 550 nm, at which the highest performance for styrene hydrogenation was obtained. The improved photoredox activity of the title nanohybrid could be caused by the synergistic effects of the heterojunction of carbon nitride-Pd on TiO2 nanoparticles evidenced by photoluminescence spectra and catalytic reactions. The catalyst proved to be air-stable, robust, recyclable, and very active in the absence of any undesirable additives and reducing agents. Thus, this work presents a new protocol for improving the photocatalytic properties of semiconducting materials for various photocatalytic applications under environmentally friendly conditions.

In this study, synthesis, characterization and photocatalytic performance of surface-modified TiO2 nanoparticles with ascorbic acid-stabilized Pd nanoparticles are presented. The structure, composition and morphology of as-prepared nanophotocatalyst were characterized by UV-DRS, FT-IR, ICP-AES, TEM and XPS analysis. Ascorbic acid-stabilized Pd nanoparticles induced visible light driven photocatalytic property on the surface of TiO2 which are otherwise insensitive to visible light owing to the wide band gap. The catalytic system worked well for the Suzuki–Miyaura cross-coupling and Ullmann homocoupling under compact fluorescent light as a visible source with significant activity, selectivity and recyclability. Good to excellent yields of biaryl products were obtained for various aryl halides having different electronic demands and even aryl chlorides. Our results proposed that the improved photoactivity predominantly benefits from the synergistic effects of ascorbic acid-stabilized Pd nanoparticles on TiO2 nanoparticles that cause efficient separation and photoexcited charge carriers and photoredox capability of nanocatalyst. Thus, tuning of band gap of TiO2 making a visible light sensitive photocatalyst, demonstrates a significant advancement in the photocatalytic Suzuki–Miyaura and Ullmann coupling reactions.

In this paper, a novel nickel–riboflavin nanocomplex has been prepared via the incorporation of Ni(OAc)2 with riboflavin. This new heterogeneous nanocatalyst showed high catalytic activity towards green oxidation reactions. The structural and morphological characterization of the as-prepared nanocomplex was carried out using different techniques such as FT-IR, ICP-AES, TGA, SEM, EDX, TEM, UV-vis and elemental analysis. The nano-biocatalyst showed high oxidation stability and desired activity in the aerobic benzylic oxidation of a structurally diverse set of alcohols in ethyl acetate as a safe solvent. Further, oxidation of sulfides in the presence of H2O2 was successfully achieved, producing the corresponding sulfoxides in high yields and with excellent selectivity. The facile and practical reusability of the solid catalyst at the end of the reaction was also observed.

In this study, we performed a visible light-mediated aerobic photo-cross dehydrogenative coupling (CDC) reaction between aldehydes and N-hydroxyimides using TiO2–AA–Co as a photocatalyst for the synthesis of active esters. The synergistic and selective effects of the cobalt ascorbic acid complex (Co–AA) and TiO2 nanoparticles on the visible-light photocatalytic activity were explored. The method possesses some advantages such as environmentally friendly conditions, easy work-up procedure, reusability, and scalability.

In this study, we developed methods for the one pot environmentally benign synthesis of benzimidazoles by cobalt ascorbic acid complex coated on TiO2 nanoparticles via aerobic photooxidative cyclization reactions. Easy work-up procedure, reusability of the catalyst and scalable to the multi-mole scale, which is valuable for an industrial process make these catalytic systems highly attractive. Also, the combination of photocatalytic and catalytic reactions presented here may help to develop a new strategy towards the development of photocatalysis-based organic synthesis.

Phase-transfer catalytic epoxidation activity of nanosized {Mo72Cr30} Keplerate polyoxometalate in ethanol in the presence of hydrogen peroxide is exploited. The nanocluster acts as a homogeneous catalyst upon treatment with hydrogen peroxide, while it can be easily filtered and reused as a heterogeneous catalyst. The high catalytic activity and durability of catalyst was demonstrated.

A visible-light-driven photocatalytically active nanocrystalline TiO2 was prepared by surface modification with a cobalt–ascorbic acid complex. The photocatalyst exhibited high activity and excellent chemo-, diastereo-, and stereoselectivities in the aerobic epoxidation of olefins under visible-light irradiation in the absence of a reducing agent. The catalyst proved efficient and could be recycled at least five times.

Simple Mn-salen complex was anchored coordinatively to γ-Fe2O3 nanoparticles through amine functionality which provide a new magnetically recoverable nanocatalyst with high oxidation activity and stability. Catalyst characterization was performed using FT-IR, UV-Vis, XRD, EDS, TGA and ICP-AES. TEM image revealed a quasi-spherical structure with size smaller than 20 nm for nanocatalyst. A thermal stability up to around 300 °C was verified for prepared nanocatalyst based on thermogravimetric analysis. Finally, the catalytic performance of magnetically recoverable Mn-catalyst was exploited in the green oxidation of different types of functional groups including olefins, alcohols, saturated hydrocarbons and sulfur containing compounds with n-Bu4NHSO5 (TBAOX) in water under heterogeneous conditions. The salen catalyst proved to be reusable for at least eight times and the oxidant's by-product (n-Bu4NHSO4) could also be recycled.