Photocatalytic Synthesis Research Articles

Photocatalytic Synthesis of β‐Keto Primary Chlorides by Selective Chlorocarbonylation of Olefins

AbstractFunctionalized primary alkyl chlorides are precursors to a plethora of scaffolds but their access from chemical feedstocks remains challenging. Herein, we report a concise dual Ni/photoredox catalytic protocol for regioselective chlorocarbonylation of unactivated alkenes that enables rapid access to β‐keto primary chlorides. The catalytic process features an extensive substrate scope, scalability and functional group tolerance. The Ni/photocatalytic Cl⋅ generation and subsequent cross‐coupling is implicated for the process based on the control experiments and DFT study. The synthetic utility of the protocol has been further corroborated through functionalization of complex substrates and modifications of the product.

Photocatalytic synthesis of 2,4‐substituted quinazolines via a one‐pot, three‐component reaction under catalyst‐free conditions

AbstractA novel, catalyst‐free photoinduced synthesis of 2,4‐substituted quinazoline using 2‐amino‐aryl ketone, an aldehyde, and ammonium acetate was developed. A series of 2,4‐substituted quinazoline compounds were obtained via irradiating the reactants with a light‐emitting diode light (18 W) at room temperature. The broad substrate range and excellent gram‐scale experimental results demonstrate the versatility of the reaction. To the best of our knowledge, the synthesis of 2,4‐substituted quinazoline using ammonium acetate as the nitrogen source under photocatalysis has not been reported thus far. This method utilizes visible light oxidation to eliminate the use of oxidants in the reaction and is complementary to previous methods.

Constructing 2D/2D g-C3N4/BiOCl Z-scheme heterojunction for synthesis of imines via photocatalytic coupling of benzylamine

Here, 2D/2D Z-scheme heterojunctions, BiOCl/g-C3N4 (CN-B), are successfully prepared for the photocatalytic coupling of benzylamine (BA) to N-benzylidenebenzylamine (NBA) in air atmosphere under visible light. The high conversion (96.1 %) of BA can be achieved over the optimal catalyst (CN-B-1.6), with a selectivity of NBA (95.2 %). The interface charges are redistributed on CN-B because of the strong interaction between BiOCl and g-C3N4, benefiting to the activation of substrates. The results of In situ diffuse reflectance infrared Fourier-transform spectroscopy (in situ DRIFTS), Electron paramagnetic resonance (EPR) and X-ray photoelectron spectra (XPS) reveal that O2 and BA molecules can be activated via coordinating on the interface of CN-B, thus improving the photocatalytic performance. The migrated pathway of photogenerated carriers follows the mechanism of Z-scheme heterojunction, improving the utilization of electrons-holes. Finally, we put forward a possible mechanism at a molecular scale to explain the photocatalytic pathway. This work emphasizes how to create an effective heterojunction photocatalyst for the photocatalytic organic synthesis.

Regulated Dual Defects of Bridging Organic and Terminal Inorganic Ligands in Iron-based Metal-Organic Framework Nodes for Efficient Photocatalytic Ammonia Synthesis.

Engineering advantageous defects to construct well-defined active sites in catalysts is promising but challenging to achieve efficient photocatalytic NH3 synthesis from N2 and H2O due to the chemical inertness of N2 molecule. Here, we report defective Fe-based metal-organic framework (MOF) photocatalysts via a non-thermal plasma-assisted synthesis strategy, where their NH3 production capability is synergistically regulated by two types of defects, namely, bridging organic ligands and terminal inorganic ligands (OH- and H2O). Specially, the optimized MIL-100(Fe) catalysts, where there are only terminal inorganic ligand defects and coexistence of dual defects, exhibit the respective 1.7- and 7.7-fold activity enhancement comparable to the pristine catalyst under visible light irradiation. As revealed by experimental and theoretical calculation results, the dual defects in the catalyst induce the formation of abundant and highly accessible coordinatively unsaturated Fe active sites and synergistically optimize their geometric and electronic structures, which favors the injection of more d-orbital electrons in Fe sites into the N2 π* antibonding orbital to achieve N2 activation and the formation of a key intermediate *NNH in the reaction. This work provides a guidance on the rational design and accurate construction of porous catalysts with precise defective structures for high-performance activation of catalytic molecules.

Regulated Dual Defects of Bridging Organic and Terminal Inorganic Ligands in Iron‐based Metal‐Organic Framework Nodes for Efficient Photocatalytic Ammonia Synthesis

AbstractEngineering advantageous defects to construct well‐defined active sites in catalysts is promising but challenging to achieve efficient photocatalytic NH3 synthesis from N2 and H2O due to the chemical inertness of N2 molecule. Here, we report defective Fe‐based metal‐organic framework (MOF) photocatalysts via a non‐thermal plasma‐assisted synthesis strategy, where their NH3 production capability is synergistically regulated by two types of defects, namely, bridging organic ligands and terminal inorganic ligands (OH− and H2O). Specially, the optimized MIL‐100(Fe) catalysts, where there are only terminal inorganic ligand defects and coexistence of dual defects, exhibit the respective 1.7‐ and 7.7‐fold activity enhancement comparable to the pristine catalyst under visible light irradiation. As revealed by experimental and theoretical calculation results, the dual defects in the catalyst induce the formation of abundant and highly accessible coordinatively unsaturated Fe active sites and synergistically optimize their geometric and electronic structures, which favors the injection of more d‐orbital electrons in Fe sites into the N2 π* antibonding orbital to achieve N2 activation and the formation of a key intermediate *NNH in the reaction. This work provides a guidance on the rational design and accurate construction of porous catalysts with precise defective structures for high‐performance activation of catalytic molecules.

Controlled asymmetric aggregation advances n → π* electronic transition and charge separation for enhanced photocatalytic hydrogen synthesis

Photocatalytic water splitting into hydrogen is considered as a promising approach for solar energy storage. The existing organic semiconductor photocatalysts are mainly dominated by π-conjugated covalent structures featuring π → π* electronic transition. Recent studies found that activating n → π* electronic transition is an effective strategy for improving photocatalytic activity of organic semiconductors. Nevertheless, n → π* electronic transition is generally forbidden in perfect symmetric structures. Herein, we have successfully synthesized asymmetric trithiocyanuric acid (TA) aggregates by a solvent chemistry strategy. The asymmetric degrees of TA aggregates can be greatly tuned by changing the pulling strength of solvent molecules. The asymmetric characteristic of TA aggregates increases the orbital overlap between the lone pair electrons on sulfur atoms and the adjacent π* orbitals of triazine, thus allowing n → π* electronic transition. Simultaneously, the asymmetric aggregation induces a large dipole moment, significantly improving the separation and transfer of charge carriers. After an assay of a hydrogen evolution reaction, a quantum yield of 42.9 % at 400 nm was recorded for the asymmetric TA aggregates, which is much higher than those of most existing covalent semiconductors. This study unlocks a fresh realm of artificial photosynthesis, which uses asymmetric aggregates featuring n → π* electronic transition for efficient photocatalytic hydrogen production.

Metal‐Organic Framework Catalyzed Hydrogen Atom Transfer for Photocatalytic Organic Synthetic Applications

AbstractThis concept paper aims to summarize recent research on the design and synthetic applications of metal‐organic frameworks (MOFs)‐based hydrogen atom transfer (HAT) catalysts. Functional MOFs have emerged as highly promising heterogeneous catalysts, leveraging their tunable, ordered structure and abundant active sites to enhance catalytic efficiency in various reactions. HAT, a versatile method for generating active open‐shell radical species through selective hydrogen abstraction, has been well explored in homogeneous photocatalysis. In contrast, heterogeneous HAT catalysis remains less developed, albeit their great potential in industry. This paper will provide a timely overview of the advancements in MOFs‐based HAT photocatalysis, classified according to catalytic centers including aromatic ketones, polyoxometalates, xanthene dyes, thiols, and alcohols, highlighting their design principles and practical applications in photocatalytic organic synthesis.

Photocatalytic Synthesis of (2-Tosylvinyl) Sulfides and Selenides by Graphitic Carbon Nitride

Photocatalytic Synthesis of (2-Tosylvinyl) Sulfides and Selenides by Graphitic Carbon Nitride

Engineering of local electron properties optimization in single-atom catalysts enabling sustainable photocatalytic conversion of N2 into NH3

Photocatalytic synthesis of ammonia (NH3) from nitrogen (N2) offers a promising strategy for carbon neutrality, as it avoids the energy-intensive and carbon-emitting industrial processes. The exploration of high-efficiency N2 photofixation systems for photocatalytic N2 reduction reaction (pNRR) is critical but it remains a challenge since the lack of rational structural design and atomic-level insights into molecular N2 activation mechanism. Herein, an atomically dispersed single-atom palladium (Pd) active sites decorated oxygen-deficient molybdenum oxide (Pd/MoO3-x) was creatively designed for assessing pNRR performance. Interestingly, the integration of single-atom Pd active sites in MoO3-x can significantly weaken the N≡N bond of adsorbed N2 and effectively lower the activation energy barrier during the pNRR process. This is attributed to the fact that the modified Pd single-atom sites of Pd/MoO3-x play a dominant role in the N2 spontaneous adsorption process as well as possess a remarkable photogenerated electron trapping ability, which could be assisted to inject electrons into N2 antibonding orbital, thus significantly accelerates the reaction kinetics. Consequently, the Pd/MoO3-x photocatalyst reaches an impressive NH3 yield rate of 103.2 μggcat.−1h−1, which is superior to that of pristine MoO3-x (21.2 μggcat.−1h−1) and commercial MoO3 (6.5 μggcat.−1h−1), respectively. The present study not only creates a reliable approach to expand efficient N2 photofixation system under mild conditions through the fabrication of atomically dispersed monometallic active sites, but also offers atomic-level insights into the underlying mechanism of pNRR catalytic process.

Synthesis and characterization of 3-in-1 multifunctional lipiodol-doped Fe3O4@Poly (diallyl isophthalate) microspheres for arterial embolization, chemotherapy, and imaging

Transcatheter arterial embolization plays a pivotal role in treating various diseases. However, the efficacy of embolization therapy in cancer treatment can be limited by several factors, such as inevitable incomplete or non-target embolization, and the tumor recurrence and metastasis caused by the hypoxic microenvironment. Moreover, it is essential to explore simpler, more economical, and efficient methods for microsphere synthesis. Herein, we achieved one-step photocatalytic synthesis of lipiodol-doped Fe3O4@Poly (diallyl iso-phthalate) multifunctional microspheres (IFeD MS) for arterial embolization, chemotherapy, and imaging. The prepared microspheres are in the shape of dried plums, with a particle size of 100–300 μm. Lipiodol demonstrates a certain degree of chemotherapeutic activity, and the incorporation of Fe3O4 enables the microspheres to exhibit magnetothermal response and magnetic resonance imaging capabilities. Furthermore, the radiopaque characteristics of both agents provide the microspheres with promising potential for computed tomography and digital radiography imaging. The renal embolization experiment in rabbits demonstrated that IFeD MS achieved significant embolization and chemotherapeutic effects. Biocompatibility experiments revealed that this embolic agent did not induce tissue damage or inflammation beyond the treatment area. Additionally, IFeD MS exhibited promising imaging potential. The results of this study imply that the developed multifunctional embolic agent IFeD MS may have significant potential in transforming tumors previously only suitable for palliative cares into resectable radical treatments.

Spaced Double Hydrogen Bonding in an Imidazole Poly Ionic Liquid Composite for Highly Efficient and Selective Photocatalytic Air Reductive H2O2 Synthesis.

Photocatalytic oxygen reductive H2O2 production is a promising approach to alternative industrial anthraquinone processes while suffering from the requirement of pure O2 feedstock for practical application. Herein, we report a spaced double hydrogen bond (IC-H-bond) through multi-component Radziszewski reaction in an imidazole poly-ionic-liquid composite (SI-PIL-TiO2) and levofloxacin hydrochloride (LEV) electron donor for highly efficient and selective photocatalytic air reductive H2O2 production. It is found that the IC-H-bond formed by spaced imino (-NH-) group of SI-PIL-TiO2 and carbonyl (-C=O) group of LEV can switch the imidazole active sites characteristic from a covered state to a fully exposed one to shield the strong adsorption of electron donor and N2 in the air, and propel an intenser positive potential and more efficient orbitals binding patterns of SI-PIL-TiO2 surface to establish competitive active sites for selectivity O2 chemisorption. Moreover, the high electron enrichment of imidazole as an active site for the 2e- oxygen reduction ensures the rapid reduction of O2. Therefore, the IC-H-bond enables a total O2 utilization and conversion efficiency of 94.8 % from direct photocatalytic air reduction, achieving a H2O2 production rate of 1518 μmol/g/h that is 16 and 23 times compared to poly-ionic-liquid composite without spaced imino groups (PIL-TiO2) and TiO2, respectively.

Linker gadolinium as charge channel and singlet oxygen activation site in graphitic carbon nitride for enhancing photocatalytic decomposition of tetracycline

Reactive oxygen species are essential in photocatalytic water treatment. In this paper, Gd doped carbon nitride (CN) photocatalysts were prepared by simple thermal polymerization for the photocatalytic degradation of tetracycline under visible light irradiation. The photodegradation rate of 1.0GdCN is as high as 95% in 18 min, and the photocatalytic performance is much higher than that of CN. The improvement of photocatalytic performance is mainly attributed to the fact that Gd ion implantation directly provides active sites for oxygen activation and induces the formation of N vacancies. The results of characterizations show that the introduction of Gd in CN can improve the conversion ability of activated oxygen, carrier separation and energy band structure adjustment. Therefore, 1.0GdCN photocatalyst can be employed for efficient photocatalytic synthesis of tetracycline. Furthermore, three ways of photocatalytic degradation of tetracycline were revealed by high performance liquid chromatography-mass spectrometry. This work provides insights into the doping strategy of CN to improve the production of reactive oxygen species for environmental remediation.

COF-Based Photocatalysts for Enhanced Synthesis of Hydrogen Peroxide.

Covalent Organic Frameworks (COFs), with their intrinsic structural regularity and modifiable chemical functionality, have burgeoned as a pivotal material in the realm of photocatalytic hydrogen peroxide (H2O2) synthesis. This article reviews the recent advancements and multifaceted approaches employed in using the unique properties of COFs for high-efficient photocatalytic H2O2 production. We first introduced COFs and their advantages in the photocatalytic synthesis of H2O2. Subsequently, we spotlight the principles and evaluation of photocatalytic H2O2 generation, followed by various strategies for the incorporation of active sites aiming to optimize the separation and transfer of photoinduced charge carriers. Finally, we explore the challenges and future prospects, emphasizing the necessity for a deeper mechanistic understanding and the development of scalable and economically viable COF-based photocatalysts for sustainable H2O2 production.

Reduction of Superoxide Radical Intermediate by Polydopamine for Efficient Hydrogen Peroxide Photosynthesis.

The synthesis of hydrogen peroxide through artificial photosynthesis is a green and promising technology with advantages in sustainability, economy and safety. However, superoxide radical (⋅O2 -), an important intermediate in photocatalytic oxygen reduction to H2O2 production, has strong oxidizing properties that potentially destabilize the catalyst. Therefore, avoiding the accumulation of ⋅O2 - for its rapid conversion to H2O2 is of paramount significance in improving catalyst stability and H2O2 yield. In this work, a strategy was developed to utilize protonated groups for the rapid depletion of converted ⋅O2 -, thereby the efficiency of photocatalytic synthesis of H2O2 from CN was successfully enhanced by 47-fold. The experimental findings demonstrated that polydopamine not only improved carrier separation efficiency, and more importantly, provided the adsorption reduction active site for ⋅O2 - for efficient H2O2 production. This work offers a versatile approach for synthesizing efficient and stable photocatalysts.

Reduction of Superoxide Radical Intermediate by Polydopamine for Efficient Hydrogen Peroxide Photosynthesis

AbstractThe synthesis of hydrogen peroxide through artificial photosynthesis is a green and promising technology with advantages in sustainability, economy and safety. However, superoxide radical (⋅O2−), an important intermediate in photocatalytic oxygen reduction to H2O2 production, has strong oxidizing properties that potentially destabilize the catalyst. Therefore, avoiding the accumulation of ⋅O2− for its rapid conversion to H2O2 is of paramount significance in improving catalyst stability and H2O2 yield. In this work, a strategy was developed to utilize protonated groups for the rapid depletion of converted ⋅O2−, thereby the efficiency of photocatalytic synthesis of H2O2 from CN was successfully enhanced by 47‐fold. The experimental findings demonstrated that polydopamine not only improved carrier separation efficiency, and more importantly, provided the adsorption reduction active site for ⋅O2− for efficient H2O2 production. This work offers a versatile approach for synthesizing efficient and stable photocatalysts.

Establishing carrier transport channels based on TiS bonds and enhancing the photocatalytic performance of MXene quantum dots–ZnIn2S4 for ammonia synthesis

AbstractIn the process of photocatalytic synthesis of ammonia, the kinetics of carrier separation and transport, adsorption of nitrogen, and activation of the NN triple bond are key factors that directly affect the efficiency of converting nitrogen to ammonia. Here, we report a new strategy for anchoring MXene quantum dots (MXene QDs) onto the surface of ZnIn2S4 by forming TiS bonds, which provide a channel for the rapid separation and transport of charge carriers and effectively extend the lifespan of photogenerated carriers. The unique charge distribution caused by the sulfurization of the MXene QDs further enhances the performance of the photocatalysts for the adsorption and activation of nitrogen. The photocatalytic ammonia synthesis efficiency of MXene QDs–ZnIn2S4 can reach up to 360.5 μmol g−1 h−1. Density functional theory calculations, various in situ techniques, and ultrafast spectroscopy are used to characterize the successful construction of TiS bonds and the dynamic nature of excited state charge carriers in MXene QDs–ZnIn2S4, as well as their impact on nitrogen adsorption activation and photocatalytic ammonia synthesis efficiency. This study provides a new example of how to improve nitrogen adsorption and activation in photocatalytic material systems and enhance charge carrier dynamics to achieve efficient photocatalytic nitrogen conversion.image

12 Connecting Sites Linked Three‐dimensional Covalent Organic Frameworks with Intrinsic Non‐interpenetrated shp Topology for Photocatalytic H2O2 Synthesis

AbstractDeveloping high connectivity (>8) three‐dimensional (3D) covalent organic frameworks (COFs) towards new topologies and functions remains a great challenge owing to the difficulty in getting high connectivity organic building blocks. This however represents the most important step towards promoting the diversity of COFs due to the still limited dynamic covalent bonds available for constructing COFs at this stage. Herein, highly connected phthalocyanine‐based (Pc‐based) 3D COFs MPc‐THHI‐COFs (M=H2, Ni) were afforded from the reaction between 2,3,9,10,16,17,23,24‐octacarboxyphthalocyanine M(TAPc) (M=H2, Ni) and 5,5′,5′′,5′′′,5′′′′,5′′′′′‐(triphenylene‐2,3,6,7,10,11‐hexayl)hexa(isophthalohydrazide) (THHI) with 12 connecting sites. Powder X‐ray diffraction analysis together with theoretical simulations and transmission electron microscopy reveals their crystalline nature with an unprecedented non‐interpenetrated shp topology. Experimental and theoretical investigations disclose the broadened visible light absorption range and narrow optical band gap of MPc‐THHI‐COFs. This in combination with their 3D nanochannels endows them with efficient photocatalysis performance for H2O2 generation from O2 and H2O via 2e− oxygen reduction reaction and 2e− water oxidation reaction under visible‐light irradiation (λ >400 nm). This work provides valuable result for the development of high connectivity functional COFs towards diverse application potentials.

12 Connecting Sites Linked Three-dimensional Covalent Organic Frameworks with Intrinsic Non-interpenetrated shp Topology for Photocatalytic H2O2 Synthesis.

Developing high connectivity (>8) three-dimensional (3D) covalent organic frameworks (COFs) towards new topologies and functions remains a great challenge owing to the difficulty in getting high connectivity organic building blocks. This however represents the most important step towards promoting the diversity of COFs due to the still limited dynamic covalent bonds available for constructing COFs at this stage. Herein, highly connected phthalocyanine-based (Pc-based) 3D COFs MPc-THHI-COFs (M=H2, Ni) were afforded from the reaction between 2,3,9,10,16,17,23,24-octacarboxyphthalocyanine M(TAPc) (M=H2, Ni) and 5,5',5'',5''',5'''',5'''''-(triphenylene-2,3,6,7,10,11-hexayl)hexa(isophthalohydrazide) (THHI) with 12 connecting sites. Powder X-ray diffraction analysis together with theoretical simulations and transmission electron microscopy reveals their crystalline nature with an unprecedented non-interpenetrated shp topology. Experimental and theoretical investigations disclose the broadened visible light absorption range and narrow optical band gap of MPc-THHI-COFs. This in combination with their 3D nanochannels endows them with efficient photocatalysis performance for H2O2 generation from O2 and H2O via 2e- oxygen reduction reaction and 2e- water oxidation reaction under visible-light irradiation (λ >400 nm). This work provides valuable result for the development of high connectivity functional COFs towards diverse application potentials.

Visible-Light-Initiated Catalyst-Free Radical Annulation Reactions of 1,6-Enynes and Aryl Sulfonyl Bromide to Assemble Sulfonation/Bromination Succinimide Derivatives.

In the present study, the environment-friendly visible-light-promoted strategy is used to perform an efficient, simple, and straightforward photocatalytic succinimide derivative synthesis from the reaction of 1,6-enynes and aryl sulfonyl bromide at room temperature under air ambient conditions. This method features mild conditions, broad substrate scope, high yields, and excellent configurational selectivity. In addition, all the atoms of the substrates involved in the reaction converge in the product structures, showing a high atomic economy. Moreover, the most important characteristic of this study is that no photocatalyst and additives are used, while the key factor that triggers the reaction is visible light, indicating that this study has an important practical value.

Selective photocatalytic and photoelectrocatalytic synthesis of valuable compounds in aqueous medium

In the past decades, photocatalytic and photoelectrocatalytic methods have been widely employed for the degradation of harmful compounds present both is gaseous and aqueous effluents. In the last years scientists have paid great attention to the synthesis of valuable compounds and hydrogen production. Organic syntheses are generally carried out in organic solvents, under high temperature/pressure, with toxic oxidants such as permanganate. On the other hand, photocatalysis and photoelectrocatalysis using water as solvent, air or water as oxidant, and sunlight as energy source, can be an efficient alternative to the traditional, non-environmentally friendly methods. This review summarizes the photocatalytic and photoelectrocatalytic transformations of organic molecules to commercially valuable products in water, sometimes evaluating also the contemporary H2 production. The reaction conditions, mechanisms and kinetics are presented and discussed. Future perspectives are also given.