Photocatalytic Transformation of Organics to Valuable Chemicals - Quo Vadis?

Recent development in photocatalysis is increasingly focused on transforming organic compounds toward producing fine chemicals. Simple, non-selective oxidation reactions (degradation of pollutants) and very demanding solar-to-chemical energy conversion processes (production of solar fuels) face severe economic limitations influenced by still low efficiency and insufficient stability of the systems. Synthesis of fine chemicals, including reductive and oxidative selective transformations, as well as C-C and C-N coupling reactions, can utilise the power of photocatalysis. Herein, we present the recent progress in photocatalytic systems designed to synthesise fine chemicals. In particular, we discuss the factors influencing the efficiency and selectivity of the organic transformations, dividing them into intrinsic (related to individual properties of photocatalysts) and extrinsic (originating from the reaction environment). A rational design of the photocatalytic systems, based on a deep understanding of these factors, opens new perspectives for applied photocatalysis.

Recent Advances in the Synthesis of Aromatic Azo Compounds

Aromatic azo compounds have -N=N- double bonds as well as a larger π electron conjugation system, which endows aromatic azo compounds with wide applications in the fields of functional materials. The properties of aromatic azo compounds are closely related to the substituents on their aromatic rings. However, traditional synthesis methods, such as the coupling of diazo salts, have a significant limitation with respect to the structural design of aromatic azo compounds. Therefore, many scientists have devoted their efforts to developing new synthetic methods. Moreover, recent advances in the synthesis of aromatic azo compounds have led to improvements in the design and preparation of light-response materials at the molecular level. This review summarizes the important synthetic progress of aromatic azo compounds in recent years, with an emphasis on the pioneering contribution of functional nanomaterials to the field.

Controlling Selectivity in Plasmonic Catalysis: Switching Reaction Pathway from Hydrogenation to Homocoupling Under Visible-Light Irradiation

Plasmonic catalysis enables the use of light to accelerate molecular transformations. Its application to the control reaction selectivity is highly attractive but remains challenging. Here, we have found that the plasmonic properties in AgPd nanoparticles allowed different reaction pathways for tunable product formation under visible-light irradiation. By employing the hydrogenation of phenylacetylene as a model transformation, we demonstrate that visible-light irradiation can be employed to steer the reaction pathway from hydrogenation to homocoupling. Our data showed that the decrease in the concentration of H species at the surface due to plasmon-enhanced H₂ desorption led to the control in selectivity. These results provide important insights into the understanding of reaction selectivity with light, paving the way for the application of plasmonic catalysis to the synthesis of 1,3-diynes, and bringing the vision of light-driven transformations with target selectivity one step closer to reality.

Optimized synthesis of mono and bimetallic nanoparticles mediated by unicellular algal (diatom) and its efficiency to degrade azo dyes for wastewater treatment

The silver/palladium nanoparticles (Ag/Pd NPs) were efficiently absorb UV-Visible light and reveal greater photocatalytic activity as compared to monometallic NPs. The aim of this study is photodegradation of the industrial azo dye using bimetallic Ag/Pd NPs and monometallic Ag NPs in presence of UV light for wastewater treatment. Bacillariophyceae (diatom) algae extract was utilized for the green synthesized Ag and Ag/Pd NPs. Biosynthesized nanoparticles were characterized by various useful characterization techniques viz. UV-Vis, FT-IR, SEM, TEM, and XRD. The crystallite size is found to be ∼23 nm and ∼56 nm for Ag NPs and Ag/Pd NPs, respectively, which is same as results obtained from TEM analysis, as the particle size and shape were analyzed as ∼27 and ∼56 nm, with a spherical geometry. The NPs was used to develop the optimization parameters for dye degradation such as time, temperature, and NP concentrations. A total 15 runs were considered for the study and procured by statistical software. Response surface methodology technique was implied and Box-Behnken design (BBD) design was built into the workflow. The results of the present study manifested a good connection between experimental and predicted values (R² = 0.9838). Therefore, present study promises that the prepared NPs possess excellent photocatalytic activity against harmful dyes.

Copper(i) oxide nanoparticle-mediated C–C couplings for synthesis of polyphenylenediethynylenes: evidence for a homogeneous catalytic pathway

Polyphenylenediethynylenes have been synthesized using copper(i) oxide nanocatalysts under ligandless conditions, mild base, and atmospheric air as the oxidant in good yield and number average molecular weight.

Visible-light triggered selective reduction of nitroarenes to azo compounds catalysed by Ag@organic molecular cages

Herein, a new Ag nanoparticle (Ag NP) loaded organic molecular cage is reported. The obtained Ag@1 can act as a highly efficient heterogeneous catalyst for the selective reduction of nitroarenes to azo compounds under visible-light irradiation.