Photocatalytic Conditions Research Articles

N-Trifluoroethoxy Benzotriazolium Triflate: A Readily Available Reagent for Direct Radical Trifluoroethoxylation of Alkenes.

Herein, we describe the development and application of a novel benzotriazole-based reagent toward radical trifluoroethoxylation. Various alkene classes, including styrene derivatives, enol carbonates, and allyl silanes, are viable reaction partners in this transformation, yielding diverse trifluoroethoxylated products. Furthermore, this method is readily applicable for the late-stage modification of natural product and drugs molecules. Mechanistic and computational studies suggest the intermediacy of an OCH2CF3 radical generated under photocatalytic conditions.

Selective Functionalization of White Phosphorus with Alkyl Bromides under Photocatalytic Conditions: A Chlorine-Free Protocol to Dialkyl and Trialkyl Phosphine Oxides.

A novel and efficient method for the direct selective alkylation of white phosphorus (P4) with alkyl bromides has been developed, utilizing 4DPAIPN as the photocatalyst and Hantzsch ester as the reductant. This method facilitates the synthesis of structurally diverse dialkyl phosphine oxides in good yields, offering a streamlined alternative to the traditional stepwise approach of chlorinating P4 with Cl2 and subsequently displacing the chlorine atom. Noteworthy features of this reaction include excellent product selectivity, remarkable functional group tolerance, and a broad substrate scope. Additionally, this method is effective for the synthesis of trialkyl phosphine oxides.

Decarboxylative Xanthylation under Photocatalytic Conditions.

Xanthates are widely used in organic synthesis for the construction of various molecules and have numerous applications as bioactive compounds. Here, we present their preparation via a straightforward photocatalytic decarboxylative xanthylation process involving readily available oxime esters and xanthate dimers. This approach provides access to a wide variety of xanthate compounds in moderate to good yields, including xanthates derived from relevant pharmaceutical and bioactive molecules.

Visible Light Mediated Difluoroalkylation of Alkenes Using Mercaptobenzothiazole‐Derived Sulfide Reagent

AbstractA method for the reductive difluoromethylation of alkenes with 2‐difluoromethylthio(benzothiazole) under photocatalytic conditions is described. The reaction involves the generation of the difluoromethyl radical by means of trimethyltriazinane, which serves as a precursor for the strongly reducing cyclic diaminoalkyl radical.

Novel Metal‐Free Porphyrin with Ionic Liquid and Sulphonic Acid Moieties for Visible Light Assisted Photocatalytic C‐N Coupling of Heterocyclic Compounds with Aryl Halides

Metal‐free Buchwald‐Hartwig type photocatalytic approach for N‐substitution of 1,2,4‐triazole at normal temperature was explored for the first‐time using novel imidazolium based Brønsted acid functionalized porphyrin (ImBAFPc). The energy band gap and Hammett acidity were determined by UV‐Vis spectrophotometer. The energy band gap, 1.06 eV supported absorption of radiation in the visible region. The N‐arylation of 1,2,4‐triazole with various Ar‐X was achieved in a home‐made photoreactor by heterogeneous, recyclable ImBAFPc photocatalyst under irradiation of 5W LED with good yields. The protocol tolerated electron donating and attracting Ar‐X, including inactivated chlorobenzene, affording the arylated triazole with admirable yields. under ambient photocatalytic conditions.

SPR Effect Enables Flexible Electronic Environment and Activity of Cd0.7In2.2S4-30 for High-Performance Pyro-PEC Catalytic Capability.

Plasma-semiconductor systems hold significant promise in the field of photoelectrocatalysis. In this study, the pyroelectric material cadmium indium sulfide (Cd0.7In2.2S4-30) and Pt were used as catalysts, and a temperature gradient was introduced to investigate the influence of surface plasmon resonance (SPR) effect on the pyroelectric and photocatalytic performance. Interestingly, under the influence of the SPR effect, Cd0.7In2.2S4-30 demonstrates a 1.6-fold and 1.4-fold increase in current density under photocatalytic and pyro-photoelectrocatalytic conditions at 1.23 V vs RHE, respectively. Furthermore, under the protection of surface metal Pt, a notable enhancement in the charge separation efficiency and stability of the photoelectrode material is observed. The combination of outstanding performance reveals that Pt noble metal ions, influenced by the SPR effect, generate a localized electric field at the adjacent semiconductor interface, enhancing the charge transfer capability between metal nanoparticles and the semiconductor, thereby promoting electron-hole separation and improving semiconductor photocatalytic activity. Additionally, the SPR effect increases the yield of high-energy pyro-electrons on plasma metal and facilitates their effective transfer to the semiconductor, thereby promoting the generation of thermally induced electrons. This study reveals the multifaceted of SPR effects on the behaviors of semiconductors and provides an opportunity to rationally design metal-semiconductor photocatalytic materials for efficient solar energy conversion.

Preparation of Soybean Dreg-Based Biochar@TiO2 Composites and the Photocatalytic Degradation of Aflatoxin B1 Exposed to Simulated Sunlight Irradiation.

Aflatoxin B1 (AFB1) is a highly toxic carcinogen severely harmful to humans and animals. This study fabricated SDB-6-K-9@TiO2 composites via the hydrothermal synthesis method to reduce AFB1. The structural characterization results of the photocatalytic composites showed that TiO2 was successfully loaded onto SDB-6-K-9. The different photocatalytic degradation conditions, photocatalyst kinetics, recycling performance, and photocatalytic degradation mechanism were investigated. Photocatalysis with 6 mg of 4%SDB-6-K-9@TiO2 in a 100 μg/mL AFB1 solution presented a reduction of over 95%, exhibiting excellent performance, high stability, and reusability even after five cycles of photocatalytic experiments. Active species trapping experiments confirmed that holes (h+) played the most critical role. After structural analysis and identification of the photocatalytic degradation products, the photodegradation path and photocatalytic oxidation mechanism of 4%SDB-6-K-9@TiO2 were postulated. The results show a new way to improve TiO2's photocatalytic performance, providing a certain theoretical basis for the effective AFB1 reduction.

CuOx supported LaCoO3 perovskite for the photoassisted reverse water gas shift reaction at low temperature

CuOx/LaCoO3 systems have been studied for the rWGS reaction under thermal assisted photocatalytic conditions within low temperature range of 180–330 ºC. CuOx species deposited from chemical reduction method over LaCoO3 homogeneously covered the perovskite surface. The reduction pretreatment before reaction leads to the partial Co reduction and the complete reduction of Cu. A significant improvement on CO production has been attained upon Cu incorporation. In addition, upon UV–vis irradiation the CO production is also enhanced. Best results have been obtained for 5 wt% Cu. The highest synergistic effect was observed for the lowest temperature, for which catalytic contribution is negligible. Thus, a good compromise is attained at 300 ºC for which a CO production of 5.45 mmol/h·g and 92 % selectivity, showing a good synergistic effect between thermo and thermo-photocatalytic activity.

Photocatalyzed Imino-Difluoromethylation of Alkenes with Bifunctional Oxime Esters.

Herein, we report a simple and versatile difluoromethylene-imide reaction in which a series of olefins can undergo a difluoromethylenimine reaction under photocatalytic conditions through an energy transfer (EnT) process. The reaction has mild conditions and a wide range of applicability. We successfully synthesized 27 molecules containing difluoromethylene units, featuring easily accessible starting materials and operational simplicity.

Sodium Hypophosphite as a Halogen Atom Transfer (XAT) Agent under Photocatalytic Conditions.

The ability of sodium hypophosphite to generate the phosphorus-centered radical, which can activate the carbon-halogen bond via the halogen atom transfer (XAT) is described. The hydroalkylation of nonactivated alkenes with methyl bromoacetate was performed using sodium hypophosphite as reducing agent under photocatalytic conditions. The key phosphorus centered radical is formed from the hypophosphite anion by hydrogen atom abstraction.

Spin States Matter─from Fundamentals toward Synthetic Methodology Development and Drug Discovery.

ConspectusThe potent reactivity of carbenes and nitrenes has been traditionally harnessed by the employment of a transition-metal catalyst in which the reactivity of the metal carbene/nitrene intermediates can be controlled via the judicious tuning of the metal catalyst. In recent years, progress made in this research area has unveiled novel strategies to directly access free carbenes or nitrenes under visible-light-mediated conditions without the necessity of a metal catalyst for stabilization of the carbene/nitrene intermediate. Such photochemical approaches present new opportunities to leverage orthogonal reactions with classic metal-catalyzed transformations.In this Account, we describe the major contributions from our group over the past years pushing the boundaries of light-mediated carbene and nitrene transfer reactions. In the first section, the development from purely singlet carbene chemistry toward methods that allow access to triplet carbene intermediates will be dissected. We describe how the triplet spin state of reagents provides a rich array of novel synthetic methods that build on the fundamentals of spin conservation. We lay out the different strategies in accessing the triplet spin state of carbenes (i.e., via electronic stabilization, via triplet sensitization with suitable photocatalysts, or via exploitation of geometric features of these intermediates), followed by an analysis of how the triplet spin state can be employed to leverage reactions distinct to the classic singlet carbene chemistry.The second part focuses on free nitrene intermediates, whereby both photochemical and photocatalytic strategies are analyzed and compared. We initiate with a discussion of the reactivity of iminoiodinanes as nitrene precursors in the presence of a photocatalyst or under photochemical conditions and how these two approaches result in fundamentally distinct nitrogen-based intermediates. While a nitrene radical anion is formed under photocatalytic conditions, triplet nitrene is generated under photochemical conditions. We commence with an outline of the basic reactivity of nitrene transfer reactions under both conditions, with a focus on the reaction with substrates containing double bonds. Finally, the latest developments in advanced cycloaddition chemistry beyond classic aziridination reactions are examined, with a special emphasis on the relay of the triplet nitrene reactivity to enable a Pauson-Khand-like (2 + 2 + 1) cycloaddition reaction that offers convenient access to high value bioisosteres in drug discovery.The work from our group on spin-dependent reactivities offers insight into important fundamentals in synthesis, where the spin state of the reactive intermediate will dictate the reaction outcome. We hope this may inspire others to widen the scope of applications of light-mediated carbene and/or nitrene transfer reactions, and furthermore, we anticipate that these understandings may also enable the development of advanced catalytic systems featuring triplet metal carbene/nitrene intermediates.

Synthesis of Biodegradable Medical Materials Based on Grafted Acrylate Copolymers on Collagen Obtained under Photocatalysis Conditions

Synthesis of Biodegradable Medical Materials Based on Grafted Acrylate Copolymers on Collagen Obtained under Photocatalysis Conditions

A novel all-solid-state Z-scheme BiVO4/Ag/Cu2O heterojunction: Photocatalytic and photothermal synergistic catalysis of tetracycline under simulated sunlight irradiation

The possible hazards posed by tetracycline (TC) to the environment and public health have made it a critical concern. In this work, the all-solid-state Z-scheme heterojunction BiVO4/Ag/Cu2O nanocomposites (NCs) were synthesized through a hydrothermal approach for the purpose of achieving efficient degradation towards TC. BiVO4/Ag/Cu2O NCs were able to efficiently degrade TC when exposed to simulated sunlight. The results showed that the photocatalytic efficiency was significantly influenced by Cu2O and Ag nanocrystals. The presence of Ag with large light absorption capability facilitated the efficient electron (e-) transfer between BiVO4 and Cu2O nanocrystals, thereby expanding the spectral range of light absorption in BiVO4/Cu2O NCs. Under photocatalytic and photothermal synergistic conditions, BiVO4/Ag/Cu2O NCs with an optimal addition of Ag were able to degrade TC within 60 min at reaction rate constant (k) of 0.04816 min−1. It was discovered that the best-performing photocatalysts (BAC-2) achieved photothermal conversion rates as high as 27.9 %, and they could exhibit outstanding photocatalytic and photothermal efficiency even after six cycles. Furthermore, the results obtained in radical trapping experiments suggested that photogenerated holes (h+), electrons (e-), superoxide radicals (·O2-), hydroxyl radicals (·OH) and singlet oxygen (1 O2) were involved in the photocatalytic degradation of TC. In the context of practical application, the effects of different initial TC concentrations and different irradiation conditions were studied in depth. In addition, the all-solid-state Z-scheme heterojunction mechanism for degrading TC was put forward. This research endeavors to broaden the application scope of all-solid-state Z-scheme heterojunction photocatalysts, with the aim of achieving significantly improved photocatalytic degradation of antibiotic pollutants.

Exploring novel porphyrin photocatalyst for the conversion of frying oil to biodiesel: A step for globular economy

The current protocol addresses the outcomes on the photo-transesterification of frying sunflower oil (FSO) catalysed by porphyrin comprising sulphonic acid functionalized pyridinium ionic liquid (PcSAFPyIL). A novel photocatalyst was synthesized and confirmed by 1H and 13C NMR, Powder XRD, FT-IR, XPS, and fluorescence emission spectrophotometry. The energy band gap (1.85 eV) was determined by cyclic voltammetry, Hammett acidity (H0 = 0.217) by UV–visible spectrophotometer and metal free nature by powder XRD and XPS. The photocatalytic activity of PcSAFPyIL in the visible region was confirmed by reflecting intense Soret band (421 nm) and four Q bands (515, 554, 591 and 647 nm). This may be due to inherent aromatic characters and conjugation with chromophore groups at meso-position of porphyrin ring. The obtained photocatalyst was scrutinized for the photo-transesterification of FSO in a lab-made photoreactor. The ideal reaction parameters were found to be 20 mg photocatalyst quantity with 1:12 (FSO: ROH) under exposure of 2 x 5 W LED at room temperature, to afford 90 % biodiesel in 24 h. Moreover, the formation of biodiesel was confirmed by (1H, 13C) NMR, FT-IR, DEPT-135, and GC–MS. Further, stability, heterogeneous nature and the gram scale reaction PcSAFPyIL was also efficiently accomplished using the optimized photocatalytic conditions. Additionally, the physicochemical properties of the biodiesel fuel B15 (15 % blended with marketed diesel) and pure marketed diesel are consistent. Moreover, the engine performance and emission characteristics of B15 such as brake-specific fuel consumption (BSFC), break thermal efficiency (BTE) found comparable and better than commercial diesel.

Photoredox Activation of Fluorinated Organozinc Reagents: Hydrofluoroalkylation of Unactivated and Electron Deficient Alkenes.

Hydrofluoroalkylation of alkenes with organozinc reagents under photocatalytic conditions is described. The fluorinated alkyl radicals were generated from organozincs by the single electron oxidation of the carbon-zinc bond. The radical addition step is followed either by hydrogen atom transfer for unactivated olefins or by a reduction/protonation sequence for strongly accepting arylidenemalononitriles.

Amorphous NiB layer deposition and piezoelectric field assisted for efficient photocatalytic degradation of Sb2S3

The poor surface charge reaction efficiency and electrical conductivity limit the further application of Sb2S3 in photocatalytic degradation of pollutants. An amorphous NiB layer was deposited on the surface of Sb2S3 by photo-assisted electrodeposition, and the presence of the NiB layer accelerated the charge transport and catalytic reactivity, which greatly enhanced the degradation ability. The photocurrent density of NiB-Sb2S3 was about 0.12 mA/cm2, which was 6 times of that of pure Sb2S3. After increasing the applied mechanical site by ultrasonication, the photocurrent of NiB-Sb2S3 was further increased to 0.19 mA/cm2, which was almost 9.5 times that of pure Sb2S3 under photocatalytic conditions alone. The catalytic kinetic curves show that the degradation rate of RhB by NiB-Sb2S3 under piezoelectric-photocatalytic conditions is significantly increased, being 11.48 times of the degradation rate of Sb2S3 under photocatalytic conditions. The detailed experimental data indicate that the amorphous NiB layer not only changes the electronic structure of the catalyst surface, but also increases the number and activity of the catalyst active sites, and reduces the chance of electron and hole recombination after photoexcitation. The introduction of an applied piezoelectric field provided a driving force for carrier migration to the catalyst surface, which further improved the separation ability. This study provides a new strategy to further improve the photocatalytic degradation.

NH2-MIL-125(Ti-Zr) synergized with WO3 to construct S-Scheme heterojunction photocatalysts for highly efficient degradation of organic dyes and tetracycline in water

The rapid treatment of organic dyes and tetracycline (TC) in industrial wastewater requires highly efficient semiconductor photocatalysts. In this study, the S-Scheme NH2-MIL-125 (Ti-Zr)/ WO3 composite material was successfully synthesized using a two-step hydrothermal method. A comprehensive analysis using X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), High Resolution Transmission Electron Microscopy (HRTEM), and Field Emission Scanning Electron Microscopy (FESEM) images revealed that WO3 nanoparticles are intimately anchored on the NH2-MIL-125 (Ti-Zr) nanodisks, forming a closely packed heterostructure. The bandgap values of WO3 and NH2-MIL-125 (Ti-Zr) were determined to be 2.58 eV and 2.67 eV, respectively. Through Response Surface Methodology (RSM), the optimal photocatalytic conditions for the degradation of simulated pollutants in real aqueous environments by the synthesized photocatalysts were explored. Under the full-spectrum irradiation of a 300 W xenon lamp, the TZW-2 composite photocatalyst exhibited a degradation rate of RhB, MB, and TC solutions as high as 95.7 %, 96.7 %, and 93 % within 90 min, respectively. The excellent photocatalytic performance of the composite photocatalyst originates from the establishment of S-scheme heterojunctions between NH2-MIL-125 (Ti-Zr) and WO3, which was confirmed by various characterization techniques such as XPS valence spectra, photoelectrochemistry, and free radical trapping experiments. The excellent stability of the prepared composite photocatalyst was further validated through three cycling test experiments. This work presents new ideas for constructing novel S-Scheme photocatalysts by combining bimetallic cluster MOFs and metal oxides for wastewater treatment.

Visible-Light-Induced Dearomative Annulation of Indoles toward Stereoselective Formation of Fused- and Spiro Indolines.

Dearomatization approaches are attractive for their abilities to transform simple, planar arenes into complex, three-dimensional architectures. In particular, visible-light driven dearomatization strategies are significant because of their mild, green, and sustainable nature, enabling the fabrication of new chemical bonds via an electron transfer or energy transfer process. Indole compounds, being potentially bioactive and readily accessible, can be employed efficiently as building blocks for constructing diverse annulated frameworks under photocatalysis. Highly stereoselective radical cascade reactions of appropriate indole systems can provide complex cyclic scaffolds bearing multiple stereocenters. In fact, the past few years have witnessed the renaissance of dearomative cycloadditions of indoles via visible-light-induced photocatalysis. The present review highlights recent advances (2019-mid 2024) in visible-light-driven dearomative annulation of indoles leading to formation of polycyclic indolines, including angularly fused and spiro indolines. Most of the reactions described in this review are simple, providing quick access to the desired products. Additionally, characteristic reaction mechanisms are offered to provide an understand of how indole scaffolds show distinctive reactivity under photocatalytic conditions.

Photocatalytic degradation of methylene blue under visible light using carbon-doped titanium dioxide as photocatalyst

A visible light-active photocatalyst, carbon-doped titanium dioxide (C-doped TiO2) with an anatase phase, was synthesized using a simple and cost-effective method, with glucose serving as the carbon source for doping. The surface morphology, crystal structure and elemental composition of the catalyst was analyzed by SEM, XRD and EDX respectively. Raman spectroscopic and XRD analysis showed the consistency of the anatase phase throughout the preparation process. FT-IR, TGA, and EDX depicted the purity of the prepared catalyst. SEM images revealed that the average particle size of the catalyst is approximately 178 nm, which is smaller than that of pure TiO2. Finally, as a proof-of-concept photocatalytic activity of the catalyst was investigated on a typical organic dye, methylene blue, under two different light sources (UV light and visible light) by varying the catalyst amount, the concentration of dye, and pH of the degrading medium. Results showed that the prepared C-doped TiO2 shows a promising result under the visible light irradiation which seems limited in case of pure TiO2. The optimum photocatalytic degradation conditions are pH 3, catalyst dosage 0.15 g, and dye concentration 3 × 10−5 M. At optimum conditions visible light shows 53 % degradation and UV light degrades almost all the dye molecules. The enhanced photocatalytic activity of C-doped TiO2 in visible light is due to carbon doping, which reduces the bandgap energy and enables the absorption of visible light photons. This convenient technique can be a great solution for the removal of dyeing wastes economically using low-cost visible light or sunlight and large scale production for industrial application.

Investigation of Cu-Oxidation and Its Roles in Unassisted CO2 Reduction and Electrochemical Oxygen Evolution

Sunlight-driven photocatalytic CO2 reduction to CO under unassisted (unbiased) conditions was recently demonstrated using heterostructured catalysts that combine p-type GaN with plasmonic Au nanoparticles and Cu nanoparticle co-catalysts (p-GaN/Al2O3/Au/Cu) [1]. However, the exact oxidation state of Cu and the hole transfer directionality between Au and Cu remain under debate. Here, we combine computational and experimental efforts to investigate the different oxidation states of Cu under unassisted photocatalytic operating conditions. Experimentally we found that the Cu nanoparticles are primarily composed of Cu2O and CuO, CuCO3.Cu(OH)2 species, with no detectable metallic Cu present. The calculated bulk thermodynamics confirmed the high stability of CuCO3.Cu(OH)2 which is also validated by its largest contribution in the Pourbaix diagram, consistent with experimental observations. To gain insights into the origin of charge transfer, we simulate material interfaces namely, Au/CuO, Au/Cu2O, and Au/CuCO3.Cu(OH)2. Our theoretical analysis supports experimentally observed light-driven hole transfer from Au to Cu.More recently significant progress has been made in understanding copper oxide (CuO) behavior at oxidizing electrochemical conditions (> 1.5 V) [2]. In our study, we show CuO transforms into the OER active phase CuOOH, as evident in the bulk Pourbaix diagram presented here. Our calculations show a novel square planar, non-magnetic CuOOH phase. This discovery is supported by calculated Raman spectroscopic analysis, revealing distinct features corresponding to Cu3+ species at 567 and 585 cm-1, closely matching experimental peaks at 587 cm-1. These findings provide insights into the electrochemical properties of copper oxide phases and their relevance towards electrocatalytic OER. Acknowledgments:This material is based on work performed by the Liquid Sunlight Alliance, which is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Fuels from Sunlight Hub under Award Number DE-SC0021266. Reference:[1] H. A. Atwater et al. ACS Energy Lett, 6, 1849 (2021)[2] M J. Janik et al. ACS Appl. Mater. Interfaces, 15, 27878 (2023)