Enhancing Photocatalysis: Understanding the Mechanistic Diversity in Photocatalysts Modified with Single-Atom Catalytic Sites.

Surface modification of heterogeneous photocatalysts with single-atom catalysts (SACs) is an attractive approach for achieving enhanced photocatalytic performance. However, there is limited knowledge of the mechanism of photocatalytic enhancement in SAC-modified photocatalysts, which makes the rational design of high-performance SAC-based photocatalysts challenging. Herein, a series of photocatalysts for the aerobic degradation of pollutants based on anatase TiO modified with various low-cost, non-noble SACs (vanadate, Cu, and Fe ions) is reported.

Robust Light Driven Enzymatic Oxyfunctionalization via Immobilization of Unspecific Peroxygenase.

Unspecific peroxygenases have attracted interest in synthetic chemistry, especially for the oxidative activation of C-H bonds, as they only require hydrogen peroxide (H O ) instead of a cofactor. Due to their instability in even small amounts of H O , different strategies like enzyme immobilization or in situ H O production have been developed to improve the stability of these enzymes. While most strategies have been studied separately, a combination of photocatalysis with immobilized enzymes was only recently reported.

Photocatalytic Synthesis of Hydrogen Peroxide from Molecular Oxygen and Water.

Hydrogen peroxide is a powerful and green oxidant that allows for the oxidation of a wide span of organic and inorganic substrates in liquid media under mild reaction conditions, and forms only molecular water and oxygen as end products. Hydrogen peroxide is therefore used in a wide range of applications, for which the well-documented and established anthraquinone autoxidation process is by far the dominating production method at the industrial scale. As this method is highly energy consuming and environmentally costly, the search for more sustainable synthesis methods is of high interest.

Intensification of Photobiocatalytic Decarboxylation of Fatty Acids for the Production of Biodiesel.

Light-driven biocatalytic processes are notoriously hampered by poor penetration of light into the turbid reaction media. In this study, wirelessly powered light-emitting diodes are found to represent an efficient and scalable approach for process intensification of the photobiosynthetic production of diesel alkanes from renewable fatty acids.

Modeling and simulation-based design of electroenzymatic batch processes catalyzed by unspecific peroxygenase from A. aegerita.

Unspecific peroxygenases have attracted interest due to their ability to catalyze the oxygenation of various types of C-H bonds using only hydrogen peroxide as a cosubstrate. Due to the instability of these enzymes at even low hydrogen peroxide concentrations, careful fed-batch addition of the cosubstrate or ideally in situ production is required. While various approaches for hydrogen peroxide addition have been qualitatively assessed, only limited kinetic data concerning enzyme inactivation and peroxide accumulation has been reported so far.

Artificial Light-Harvesting Complexes Enable Rieske Oxygenase Catalyzed Hydroxylations in Non-Photosynthetic cells.

In this study, we coupled a well-established whole-cell system based on E. coli via light-harvesting complexes to Rieske oxygenase (RO)-catalyzed hydroxylations in vivo. Although these enzymes represent very promising biocatalysts, their practical applicability is hampered by their dependency on NAD(P)H as well as their multicomponent nature and intrinsic instability in cell-free systems.

Product recovery of an enzymatically synthesized (-)-menthol ester in a deep eutectic solvent.

Deep eutectic solvents (DESs) have gained increased attention as alternative reaction media for biocatalysis in recent years. There are many investigations on biotransformations in a variety of DESs, but the purification of bioproducts from DES reaction mixtures has not yet been sufficiently addressed. The present study demonstrates a product recovery strategy from a DES reaction medium composed of (-)-menthol and dodecanoic acid.

Kinetics and Optimization of the Photocatalytic Reduction of Nitrobenzene.

The photocatalytic reduction of nitrobenzene to aniline in alcoholic solutions appears as an interesting alternative to the classical hydration. However, little is known about the influence of reaction parameters on the kinetics of the reaction which were therefore studied herein. The effects of light intensity, catalyst concentration, initial concentration, and temperature were systematically investigated under more than 50 different conditions and accurately described with an appropriate kinetic model.

A Holistic Approach to Model the Kinetics of Photocatalytic Reactions.

Understanding and modeling kinetics is an essential part of the optimization and implementation of chemical reactions. In the case of photocatalytic reactions this is mostly done one-dimensionally, i.e.

Hydrocarbon Synthesis via Photoenzymatic Decarboxylation of Carboxylic Acids.

A recently discovered photodecarboxylase from Chlorella variabilis NC64A ( CvFAP) bears the promise for the efficient and selective synthesis of hydrocarbons from carboxylic acids. CvFAP, however, exhibits a clear preference for long-chain fatty acids thereby limiting its broad applicability. In this contribution, we demonstrate that the decoy molecule approach enables conversion of a broad range of carboxylic acids by filling up the vacant substrate access channel of the photodecarboxylase.

Grafted iron(iii) ions significantly enhance NO oxidation rate and selectivity of TiO for photocatalytic NO abatement.

Semiconductor photocatalysis could be an effective means to combat nitrogen oxides (NO ) based air pollution through mineralisation of NO to nitrate. However, most of the typically TiO-based catalysts employed show a much higher reactivity towards NO than NO, leading to an accumulation of this unwanted and toxic intermediate. By grafting the photocatalyst with small amounts (≤0.

On the underlying mechanisms of the low observed nitrate selectivity in photocatalytic NO abatement and the importance of the oxygen reduction reaction.

Semiconductor photocatalysis could be an effective means to combat air pollution, especially nitrogen oxides, which can be mineralized to nitrate. However, the reaction typically shows poor selectivity, releasing a number of unwanted and possibly toxic intermediates such as nitrogen dioxide. Up to now, the underlying principles that lead to this poor selectivity were not understood so a knowledge-based catalyst design for more selective materials was impossible.

Selective Activation of C-H Bonds in a Cascade Process Combining Photochemistry and Biocatalysis.

Selective oxyfunctionalizations of inert C-H bonds can be achieved under mild conditions by using peroxygenases. This approach, however, suffers from the poor robustness of these enzymes in the presence of hydrogen peroxide as the stoichiometric oxidant. Herein, we demonstrate that inorganic photocatalysts such as gold-titanium dioxide efficiently provide H O through the methanol-driven reductive activation of ambient oxygen in amounts that ensure that the enzyme remains highly active and stable.

Properties and photochemistry of valence-induced-Ti(3+) enriched (Nb,N)-codoped anatase TiO2 semiconductors.

Nb and N codoped TiO2s are outstandingly versatile semiconductor oxides. Their high conductivity makes them valid alternatives to commercially available, but very expensive, conductive oxides. They show increased photonic efficiencies compared to the cases of solely Nb or N doped TiO2, when used as visible light sensitised photocatalysts.

Ruthenium-modified zinc oxide, a highly active vis-photocatalyst: the nature and reactivity of photoactive centres.

We recently reported a highly active photocatalyst, ruthenium-modified zinc oxide, which was found to be able to utilise the red part of the visible light spectrum for photocatalytic reactions [Bloh et al., Environ. Sci.

Transition metal-modified zinc oxides for UV and visible light photocatalysis.

In order to use photocatalysis with solar light, finding more active and especially visible light active photocatalysts is a very important challenge. Also, studies of these photocatalysts should employ a standardized test procedure so that their results can be accurately compared and evaluated with one another. A systematic study of transition metal-modified zinc oxide was conducted to determine whether they are suitable as visible light photocatalysts.