Copper‐Bridged Tetrakis(4‐ethynylphenyl)ethene Aggregates with Photo‐Regulated 1O2 and O2.− Generation for Selective Photocatalytic Aerobic Oxidation

Active species regulation is a key scientific issue that essentially determines the selectivity and activity of a photocatalyst. Herein, CuI-bridged tetrakis(4-ethynylphenyl)ethene aggregates (T4EPE-Cu) with photo-regulated 1O2 and O2.− generation were demonstrated for selective photocatalytic aerobic oxidation. In this system, transient photovoltage combined with the density functional theory calculations confirmed that Cu-alkynyl was the main oxygen activation site. The adsorbed O2 tends to produce O2.− because of the potential well effect of Cu-alkynyl under high-energy light excitation. But under low-energy light, O2 tends to produce 1O2 via resonance energy transfer with Cu-alkynyl. For α-terpinene oxidation, the ratios of 1O2 products to O2.− products can be controlled from 1.3 (380 nm) to 10.7 (600 nm). Furthermore, T4EPE-Cu exhibited ultrahigh photocatalytic performance for Glaser coupling and benzylamine oxidation, with a conversion and selectivity of over 99 %.

Solvent-controlled synthesis of Ti-based porphyrinic metal-organic frameworks for the selective photocatalytic oxidation of amines.

Facile synthesis of 2D covalent organic frameworks for cooperative photocatalysis with TEMPO: The selective aerobic oxidation of benzyl amines

Selective photocatalytic aerobic oxidation, which can be conducted under ambient conditions, is of great importance towards achieving sustainable chemistry. However, its practical applications are undermined by several challenges, such as low selectivity, sluggish reaction rates, and the requirement of UV light irradiation. Herein, we report a new concept of synergistic photocatalytic oxidation, for which two seemingly irrelevant reactions can be achieved in one photocatalytic system through the synergistic interplay of reactants and catalyst. As proof of concept, two challenging reactions, the aerobic oxidation of sulfide and the aerobic oxidative formylation of amine with methanol, were employed to demonstrate such synergistic photocatalytic aerobic oxidation under visible-light irradiation. This work could pave the way for highly selective photoredox catalysis via rational design based on mechanistic insight.

The development of metal–organic framework (MOF)‐polymer composites presents a promising avenue for designing advanced functional materials, yet preserving MOF porosity and stability after modification remains challenging. Here, the study synthesizes a MOF from cost‐effective precursors under mild conditions and functionalizes it in situ covalent porphyrinic polymer layer via visible‐light irradiation, eliminating the need for additional reagents. The resulting composite, CPhP@UiO‐66(Ce)‐NH 2 , is extensively characterized using FT‐IR, XRD, SEM/EDX, HRTEM, BET, XPS, UV–vis DRS, EPR, transient absorption spectroscopy, and solid‐state 13 C NMR spectroscopy. Under low‐energy LED light, the composite efficiently generates reactive oxygen species (ROS), enabling the additive‐free aerobic oxidation of vanillyl alcohol (a lignin model monomer) to vanillin with high selectivity and conversion, outperforming both the parent MOF and reported systems. This work introduces a novel, biomimetic strategy for constructing macrocycle‐inspired MOF‐polymer hybrids, demonstrated for the first time in selective photocatalytic aerobic oxidation. The findings advance the design of MOF‐based materials for sustainable catalysis and green chemistry applications.

Carbon black is chemically modified by selective photocatalytic oxidation, removing amorphous carbon and functionalizing the graphitic fraction to produce porous, graphitized carbon black, commonly used as an adsorbent in chromatography. In contrast to pyrolytic treatments, this photocatalytic modification proceeds under mild reaction conditions using oxygen, nitric oxide, water vapor and a titanium dioxide photocatalyst at 150 °C. The photo-oxidation can be performed both with the photocatalyst in close proximity (contact mode) or physically separated from the carbon. Structural analysis of remotely photo-oxidized carbon black reveals increased hydrophilic properties as compared to pyrolysis at 700 °C in a N2 atmosphere. Carbon black photo-oxidation selectively mineralizes sp3-hybridized carbon, leading to enhanced graphitization. This results in an overall improved structural ordering by enriching carbon black with sp2-hybridized graphitic carbon showing decreased interplanar distance, accompanied by a twofold increase in the specific surface area. In addition, the photo-oxidized material is activated by the presence of oxygen functionalities on the graphitic carbon fraction, further enhancing the adsorptive properties.

Anchoring dye onto 1D Nb2O5 in cooperation with TEMPO for the selective photocatalytic aerobic oxidation of amines

Modulating oxygen vacancies on bismuth-molybdate hierarchical hollow microspheres for photocatalytic selective alcohol oxidation with hydrogen peroxide production

0D/2D CuFe2O4/MXene Z-scheme heterojunction for improved photocatalytic selective oxidation reaction

The assembly of TiO2 surface with 1-hydroxy-2-naphthoic acid can give rise to an apparent red-shift of its absorption band, and subsequently engender the selective aerobic oxidation of sulfides triggered by visible light.

Inserting acetylene into an olefin-linked covalent organic framework for boosting the selective photocatalytic aerobic oxidation of sulfides

Photocatalytic selective amines oxidation coupled with H2O2 production over hyper-cross-linked polymers

Synthesis of organic compounds often necessitates rigorous reaction conditions or the involvement of hazardous oxidants, resulting in substantial energy consumption and considerable environmental damage. Photocatalytic selective oxidation represents a green and environmentally friendly way to obtain high‐value chemicals, which has developed rapidly in recent years. Bismuth‐based (Bi‐based) semiconductor materials have gained intense interest in selective organic synthesis due to their diverse crystal structures and compositions, tunable band structure, and outstanding photocatalytic performance. Herein, a systematic summary of the solar‐driven selective oxidation over varieties of Bi‐based semiconductors is provided. Initially, the reactive species involved in selective oxidation, Bi‐based materials widely used in photocatalytic selective oxidation, and the methods for synthesizing these Bi‐based materials are meticulously classified. Concerning their selective oxidation reactions, a variety of modification strategies, with a focus on the separation of photogenerated carriers and the regulation of reactive species is extensively documented. Highlights are the diverse applications and mechanism discussions of Bi‐based photocatalysts in the oxidation reactions, including alcohol oxidation, C─H bond activation, amine oxidation, and sulfide oxidation, as well as the coupling reactions with photoreduction. Finally, the future development prospects and challenges of Bi‐based photocatalysts in the field of selective oxidation is proposed, hoping to provide valuable insights and guidance for the design of photocatalysts for selective oxidation.

Selective oxidation of benzyl alcohol into benzaldehyde in anoxic acidic aqueous solution, through a TiO2/Cu(II)/solar UV photocatalytic system, has been investigated both in a laboratory scaled reactor equipped with a high-pressure mercury lamp as well as in a solar pilot plant. During the laboratory experiments, benzaldehyde gave best results, in terms of yield, equal to 35% with respect to the initial benzyl alcohol concentration. A partial conversion of benzaldehyde to benzoic acid has also been observed. Traces of hydroxylated by-products have also been detected. On the basis of the formation of these species, a production of HO radicals has been thus inferred. The study has suggested that different operative parameters, such as the composition and amount of TiO2 photocatalyst, pH, ionic inorganic components in water, and the initial concentration of Cu(II) ions, play an important role in the photocatalytic selective oxidation of benzyl alcohol. The mechanism of photocatalytic selective oxidation of benzyl alcohol into benzaldehyde and benzaldehyde into benzoic acid has been investigated in the presence of TiO2 catalyst and cupric ions, as electron acceptor, in water at a pH = 2.0 and under deaerated conditions. A competitive adsorption has been proposed in which the aromatic substrates are adsorbed on the TiO2 surface and react with the positive holes. Whereas Cu(II) ions are reduced to Cu(0) by the photogenerated electrons. A new kinetic model has been developed by writing a set of mass balance equations for the main species involved in the photocatalytic oxidation process. The resulting mathematical model has been used for the analysis of the data collected at different starting substrates’ concentrations. During each of the selective photoxidation runs, it satisfactorily predicts the concentrations of Cu(II) species, organic substrates, and intermediates. The effect of ionic components, which compete with benzyl alcohol and benzaldehyde for the reaction with positive holes on the catalyst surface and behave as scavengers towards HO radicals, has been taken into account in the model. The values of some rate constants of the reactions of the holes with benzyl alcohol, benzaldehyde, Cu(II) species, and inorganic anions (sulfates and di-hydrogenophosphates), not available in the literature, have been estimated by a proper optimizing procedure. 7 The conversion of hydroxybenzyl alcohols, methoxybenzyl alcohols and nitrobenzyl alcohol into the corresponding aldehydes has been attempted by using the same process. The presence and position of substituent groups in the aromatic alcohols structure change the photocatalytic oxidation rates and product selectivities with respect to that previously observed for unsubstituted benzyl alcohol. In particular, the presence of both electron donating (hydroxy, methoxy groups) and electron withdrawing (nitro group) on the aromatic ring of the substrate causes a detrimental effect on the selectivity of the process with respect to that of benzyl alcohol. The technical feasibility of selective photocatalytic oxidation of benzyl alcohol to benzaldehyde, in aqueous solutions and in presence of cupric ions, has been then investigated in a solar pilot plant with Compound Parabolic Collectors. Under deaerated conditions, the presence of reduced copper species has been proved by XPS analysis. The results indicated that, at the end of the process, cupric species can be easily regenerated and reused, through a re-oxidation of reduced copper that is produced during the photolytic run, with air or oxygen in dark conditions. A figure-of-merit (ACM), proposed by the International Union of Pure and Applied Chemistry (IUPAC) and based on the collector area, has been estimated, under the proposed conditions, with the aim to provide a direct link to the solar-energy efficiency independently of the nature of the system. Generally speaking, it can be considered that the lower ACM values are, the higher is the system efficiency.

The structure, physical characteristics and selective photocatalytic oxidation properties of quantum confined nanosize iron doped TiO2 (Q-TiO2/Fe3+) particles were studied by TG-DSC, XRD, DRS, EPR and Selective Oxidation Photocatalytic Measurements. It is shown that the solubility of iron in the obtained Q-TiO2/Fe3+ nanoparticles is 1.0 atom% and the iron doping level has a great influence on the transformation of anatase to rutile (A-R). The quantum confined effect was observed for Q-TiO2/Fe3+ nanoparticles. All of the samples have EPR Bulk-Fe3+ and Surf-Fe3+ signals, which are located in the bulk and surface of TiO2 nanoparticles respectively. Quantitative EPR results indicate that the relative EPR intensity of these paramagnetic centers shows regular change with varying corresponding iron modification level. In situ EPR indicates that the photo-generated charge carrier (h+, e−) could be trapped by different Fe3+ sites simultaneously, i.e., trapping of h+ is due to Surf-Fe3+ sites at g = 4.30, whereas that of e− is attributed to Bulk-Fe3+ sites at g = 1.99. Selective photocatalytic oxidation of cyclohexane into cyclohexanol with higher selectivity has been obtained by molecular oxygen activation over Q-TiO2/Fe3+ nanoparticles under mild conditions. It is thought that the optical surface state of Q-TiO2/Fe3+ nanoparticles play a key role in the selective photocatalytic oxidations.