Applications of Continuous-Flow Photochemistry in Organic Synthesis, Material Science, and Water Treatment

Programmed multimaterial assembly by synergized 3D printing and freeform laser induction

In nature, structural and functional materials often form programmed three-dimensional (3D) assembly to perform daily functions, inspiring researchers to engineer multifunctional 3D structures. Despite much progress, a general method to fabricate and assemble a broad range of materials into functional 3D objects remains limited. Herein, to bridge the gap, we demonstrate a freeform multimaterial assembly process (FMAP) by integrating 3D printing (fused filament fabrication (FFF), direct ink writing (DIW)) with freeform laser induction (FLI). 3D printing performs the 3D structural material assembly, while FLI fabricates the functional materials in predesigned 3D space by synergistic, programmed control. This paper showcases the versatility of FMAP in spatially fabricating various types of functional materials (metals, semiconductors) within 3D structures for applications in crossbar circuits for LED display, a strain sensor for multifunctional springs and haptic manipulators, a UV sensor, a 3D electromagnet as a magnetic encoder, capacitive sensors for human machine interface, and an integrated microfluidic reactor with a built-in Joule heater for nanomaterial synthesis. This success underscores the potential of FMAP to redefine 3D printing and FLI for programmed multimaterial assembly.

In situ Diazonium Salt Formation and Photochemical Aryl-Aryl Coupling in Continuous Flow Monitored by Inline NMR Spectroscopy

A novel class of diazonium salts is introduced for the photochemical aryl-aryl coupling to produce (substituted) biphenyls. As common diazonium tetrafluoroborate salts fail, soluble and safe aryl diazonium trifluoroacetates are applied. In this mild synthesis route no catalysts are required to generate an aryl-radical by irradiation with UV-A light (365 nm). This reactive species undergoes direct C-H arylation at an arene, forming the product in reasonable reaction times. With the implementation of a continuous flow setup in a capillary photoreactor 13 different biphenyl derivatives are successfully synthesized. By integrating an inline 19F-NMR benchtop spectrometer, samples are reliably quantified as the fluorine-substituents act as a probe. Here, real-time NMR spectroscopy is a perfect tool to monitor the continuously operated system, which produces fine chemicals of industrial relevance even in a multigram scale.

Red-Light-Driven Bifunctionalization of Styrene Derivatives

A red-light-activated phthalocyanine ruthenium complex has been designed as a catalyst for the bifunctionalization of styrene derivatives. The combination of a trifluoromethylation agent resistant to nucleophiles and various nucleophiles facilitates the concurrent incorporation of a trifluoromethyl group and various functional groups onto the double bond of the substrate. This reaction demonstrates the utility of mild, low-energy, and highly transmissive long-wavelength light for intricate molecular transformations in a one-pot procedure.

Dehydro[12]- and [18]annulene-Fused Ball-Shaped Ruthenium Complex Oligomers: Synthesis, Aromatic/Antiaromatic Effect, and Symmetry for Near-Infrared Optical Properties

The appropriate arrangement of near-infrared (NIR) chromophores allows for the modification of the peak wavelength in the NIR region and efficient use of NIR light. However, the preparation of novel NIR chromophores using simple procedures remains a formidable challenge. Herein, we report the synthesis of ball-shaped ruthenium complex oligomers. The metal complexes can be synthesized in a single step and interact strongly with NIR light. Alkyne-substituted low-symmetry ball-shaped ruthenium complexes were synthesized and subjected to Eglinton coupling to obtain dehydro[12] and [18]annulene-fused dimers and trimers. Fine-tuning of the reaction conditions led to the selective synthesis of the target oligomers. NMR spectroscopy confirmed that the 18π-aromatic and 12π-antiaromatic properties of the annulene influenced the ruthenium complex chromophore, and magnetic circular dichroism spectroscopy showed changes in the electronic structure of their excited state owing to molecular-symmetry differences. The absorption coefficient in the NIR region of the absorption spectra of the oligomers increased significantly, supporting the efficient use of light by oligomerization. The formation of oligomers using ball-shaped metal complexes is a simple and effective strategy for controlling NIR optical properties.

Ultrafast Flow Synthesis of o-Functionalized Benzenesulfonyl Fluorides and Subsequent SuFEx Connections via Lithiated Chemistry

Herein we present a flow-based, rapid, and straightforward approach to synthesize diverse functionalized sulfonyl fluorides by harnessing an aryllithium intermediate. The aryllithium intermediate was fully utilized under optimized conditions (0.016 s, -18 °C) to afford various functionalized sulfonyl fluorides and also intramolecular SuFEx cyclization products in high yields (27-94%). Furthermore, the integrated synthesis incorporating subsequent SuFEx connections with even unstable organolithium nucleophiles facilitated one-flow molecular assembly in high yields (42-72%).

Cascade Sequence of Photooxygenation-Epoxidation for the Flow Synthesis of Epoxy Alcohols

A photooxygenation-epoxidation cascade sequence converting alkenes to epoxy alcohols was developed and evaluated in batch and continuous-flow systems. In the batch system, the undesired interactions between the photooxygenation and epoxidation catalysts resulted in suboptimal yields, whereas the fine control of reaction parameters in the flow system allowed the allyl hydroperoxides produced through photooxygenation of alkenes to be rapidly converted to epoxy alcohols in yields of up to 93%. The developed procedure allows one to avoid an important synthetic bottleneck, works well where traditional batch synthesis fails, and can be scaled up to meet the needs of industrial production, thus presenting a valuable addition to the toolbox of practicing organic chemists.

Photosynthesis of C-1-Deuterated Aldehydes via Chlorine Radical-Mediated Selective Deuteration of the Formyl C-H Bond

C-1-deuterated aldehydes are essential building blocks in the synthesis of deuterated chemicals and pharmaceuticals. This has led chemists to devise mild methodologies for their efficient production. Ideally, hydrogen-deuterium exchange (HDE) is the most effective approach. However, the traditional HDE for creating C-1-deuterated aldehydes often requires a complex system involving multiple catalysts and/or ligands. In this study, we present a mild photocatalytic HDE of the formyl C-H bond with D2O. This process is facilitated by chlorine radicals that are generated in situ from low-cost FeCl3. This strategy demonstrated a broad reaction scope and high functional group tolerance, affording good yields and ≤99% D incorporation. To bridge the gap between research and industrial applications, we designed a new flow photoreactor equipped with a high-intensity light-emitting diode bucket, enabling the synthesis of C-1-deuterated aldehydes on a scale of 85 g. Finally, we successfully produced several important deuterated aldehydes that are integral to the synthesis of deuterated pharmaceuticals.

Dinuclear gold-catalyzed divergent dechlorinative radical borylation of gem-dichloroalkanes

The enormous and widespread use of organoboronic acids has prompted the development of innovative synthetic methodologies to meet the demands on structural diversity and functional group tolerance. The existing photoinduced defunctionalization radical borylation, typically focused on the conversion of one C-X bond (X= Br, I, or other leaving group) into only one C-B bond. Herein, we disclose a divergent radical dechloroborylation reaction enabled by dinuclear gold catalysis with visible light irradiation. A wide range of structurally diverse alkyl boronic, α-chloroboronic, and gem-diboronic esters can be synthesized in moderate to good yields (up to 92%). Its synthetic robustness is further demonstrated on a preparative scale and applied to late-stage diversification of complex molecules. The process hinges on a C-Cl bond relay activation in readily available gem-dichloroalkanes through inner-sphere electron transfer, overcoming the redox potential limits of unreactive alkyl chlorides.

Aziridination via Nitrogen-Atom Transfer to Olefins from Photoexcited Azoxy-Triazenes

Herein, we report that readily accessible azoxy-triazenes can serve as nitrogen atom sources under visible light excitation for the phthalimido-protected aziridination of alkenes. This approach eliminates the need for external oxidants, precious transition metals, and photocatalysts, marking a departure from conventional methods. The versatility of this transformation extends to the selective aziridination of both activated and unactivated multisubstituted alkenes of varying electronic profiles. Notably, this process avoids the formation of competing C-H insertion products. The described protocol is operationally simple, scalable, and adaptable to photoflow conditions. Mechanistic studies support the idea that the photofragmentation of azoxy-triazenes results in the generation of a free singlet nitrene. Furthermore, a mild photoredox-catalyzed N-N cleavage of the protecting group to furnish the free aziridines is reported. Our findings contribute to the advancement of sustainable and practical methodologies for the synthesis of nitrogen-containing compounds, showcasing the potential for broader applications in synthetic chemistry.

Catalytic Light-Driven Strategy for Transforming Oximes to Carbonyls

Oxime and carbonyl functional groups serve as powerful chemical hubs for constructing complex synthetic targets and valuable molecular scaffolds. In furthering this value, we report a photopromoted catalytic deoximation protocol for converting oximes and their derivatives to carbonyl functional groups. This strategic approach benefits from the use of renewable light energy input and ambient air conditions, in addition to demonstrating good substrate scope, functional group tolerance, and product yields. In offering, insights into these reactivity mechanistic studies are communicated, and the value of this protocol is further shown through one-pot operations.

Triplet-triplet annihilation photon upconversion-mediated photochemical reactions

Photon upconversion is a method for harnessing high-energy excited states from low-energy photons. Such photons, particularly in the red and near-infrared wavelength ranges, can penetrate tissue deeply and undergo less competitive absorption in coloured reaction media, enhancing the efficiency of large-scale reactions and in vivo phototherapy. Among various upconversion methodologies, the organic-based triplet-triplet annihilation upconversion (TTA-UC) stands out - demonstrating high upconversion efficiencies, requiring low excitation power densities and featuring tunable absorption and emission wavelengths. These factors contribute to improved photochemical reactions for fields such as photoredox catalysis, photoactivation, 3D printing and immunotherapy. In this Review, we explore concepts and design principles of organic TTA-UC-mediated photochemical reactions, highlighting notable advancements in the field, as well as identify challenges and propose potential solutions. This Review sheds light on the potential of organic TTA-UC to advance beyond the traditional photochemical reactions and paves the way for research in various fields and clinical applications.

Improving the capturing ability of swirl-based microfluidic chip by introducing baffle wall

Microfluidics technology is promising in developing microparticle manipulation technology due to its nondestructive control and notable adaptability. The manipulation of microparticle based on swirling stagnation point is one of the feasible microfluidics biotechnologies. Aiming to improve the regulation and control of microparticle, baffle wall is introduced into the 2-microchannel flow field. The theory of wall attachment jet is employed to elucidate the effect of baffle wall. Subsequently, finite volume method simulation is conducted by modeling the swirling flow region (SFR), and the swirling strength is calculated to characterize the SFR's particle-capturing ability. Experimental validation of the modeling and simulation methods is performed using a printed microfluidic chip, which has demonstrated exceptional reliability. Simulation results show that the baffle wall makes considerable influence on the SFR. Strikingly, a global range adjustment of stagnation point is realized when the baffle wall is configured with a convex shape, which has remarkably outperformed our previous work, where the stagnation point could only move within half range of the field. This work significantly contributes to advanced flow field structure and provides insight into better regulation of stagnation point as well as microparticles. These findings have potential applications in the analysis of the effect of bio/chemical substances on single cell.

Total Syntheses of Phorbol and 11 Tigliane Diterpenoids and Their Evaluation as HIV Latency-Reversing Agents

Tigliane diterpenoids possess exceptionally complex structures comprising common 5/7/6/3-membered ABCD-rings and disparate oxygen functionalities. While tiglianes display a wide range of biological activities, compounds with HIV latency-reversing activity can eliminate viral reservoirs, thereby serving as promising leads for new anti-HIV agents. Herein, we report collective total syntheses of phorbol (13) and 11 tiglianes 14-24 with various acylation patterns and oxidation states, and their evaluation as HIV latency-reversing agents. The syntheses were strategically divided into five stages to increase the structural complexity. First, our previously established sequence enabled the expeditious preparation of ABC-tricycle 9 in 15 steps. Second, hydroxylation of 9 and ring-contractive D-ring formation furnished phorbol (13). Third, site-selective attachment of two acyl groups to 13 produced four phorbol diesters 14-17. Fourth, the oxygen functionalities were regio- and stereoselectively installed to yield five tiglianes 18-22. Fifth, further oxidation to the most densely oxygenated acerifolin A (23) and tigilanol tiglate (24) was realized through organizing a 3D shape of the B-ring. Assessment of the HIV latency-reversing activities of the 12 tiglianes revealed seven tiglianes (14-17 and 22-24) with 20- to 300-fold improved efficacy compared with prostratin (12), a representative latency-reversing agent. Therefore, the robust synthetic routes to a variety of tiglianes with promising activities devised in this study provide opportunities for advancing HIV eradication strategies.

Continuous flow reactions in the preparation of active pharmaceutical ingredients and fine chemicals

Herein, we present an overview of continuous flow chemistry, including photoflow and electroflow technologies in the preparation of active pharmaceutical ingredients (APIs) and fine chemical intermediates. Examples highlighting the benefits and challenges associated with continuous flow processes, mainly involving continuous thermal, photo- and electrochemical transformations, are drawn from the relevant literature, especially our experience and collaborations in this area, with emphasis on the synthesis and prospective scale-up.

Recent advances and applications in high-throughput continuous flow

High-throughput continuous flow technology has emerged as a revolutionary approach in chemical synthesis, offering accelerated experimentation and improved efficiency. With the aid of process analytical technology and automation, this system not only enables rapid optimisation of reaction conditions at the millimole to the picomole scale, but also facilitates automated scale-up synthesis. It can even achieve the self-planning and self-synthesis of small drug molecules with artificial intelligence incorporated in the system. The versatility of the system is highlighted by its compatibility with both electrochemistry and photochemistry, and its significant applications in organic synthesis and drug discovery. This highlight summarises its recent developments and applications, emphasising its significant impact on advancing research across multiple disciplines.

Ultrasonic or Microwave Modified Continuous Flow Chemistry for the Synthesis of Tetrahydrocannabinol: Observing Effects of Various Solvents and Acids

Synthesizing tetrahydrocannabinol is a lengthy process with minimal yields and little applicability on an industrial scale. To close the gap between bench chemistry and industry process chemistry, this paper introduces a small-scale flow chemistry method that utilizes a microwave or ultrasonic medium to produce major tetrahydrocannabinol isomers. This process produces excellent yields and minimal side products, which leads to more efficient large-scale production of the desired cannabinoids.

Photochemical C(sp3)-H Activation for Diversity-Oriented Synthesis of 3-Functionalized Oxindoles

Heteroatom-adjacent C(sp3) radical cyclization of N-arylacrylamides provides a straightforward pathway to synthesize valuable 3-functionalized oxindoles. Traditional cyclization reactions normally require harsh conditions or transition-metal catalysts. Here, we developed a metal-free, diversity-oriented synthesis of 3-functionalized oxindoles via photochemically induced selective cleavage of C(sp3)-H bonds. A variety of 3-substituted oxindoles with functionalities such as ethers, polyhalogens, benzyl, and formyl groups can be obtained by a rational design. This strategy is characterized by its simple operation and mild conditions, aligning well with the developmental requirements for sustainable chemistry. The gram-scale continuous-flow synthesis and efficient construction of bioactive molecules highlight its practical utility.

Multiphasic Continuous-Flow Reactors for Handling Gaseous Reagents in Organic Synthesis: Enhancing Efficiency and Safety in Chemical Processes

The use of reactive gaseous reagents for the production of active pharmaceutical ingredients (APIs) remains a scientific challenge due to safety and efficiency limitations. The implementation of continuous-flow reactors has resulted in rapid development of gas-handling technology because of several advantages such as increased interfacial area, improved mass- and heat transfer, and seamless scale-up. This technology enables shorter and more atom-economic synthesis routes for the production of pharmaceutical compounds. Herein, we provide an overview of literature from 2016 onwards in the development of gas-handling continuous-flow technology as well as the use of gases in functionalization of APIs.

Synthesis of Deuterated Compounds by Flow Chemistry

Development of the efficient and practical method for the synthesis of deuterated compounds which occupies the broadest area among stable isotopes is one of the most essential issues toward the industrial advance and building a sustainable society. This review describes recent advances in deuteration reactions, where the continuous flow chemistry plays pivotal roles for the successful installation of deuterium atom into diverse organic frameworks, opening new fields of isotope-based synthetic chemistry.

At the Speed of Light: The Systematic Implementation of Photoredox Cross-Coupling Reactions for Medicinal Chemistry Research

The adoption of new and emerging techniques in organic synthesis is essential to promote innovation in drug discovery. In this Perspective, we detail the strategy we used for the systematic deployment of photoredox-mediated, metal-catalyzed cross-coupling reactions in AbbVie's medicinal chemistry organization, focusing on topics such as assessment, evaluation, implementation, and accessibility. The comprehensive evaluation of photoredox reaction setups and published methods will be discussed, along with internal efforts to build expertise and photoredox high-throughput experimentation capabilities. We also highlight AbbVie's academic-industry collaborations in this field that have been leveraged to develop new synthetic strategies, along with discussing the internal adoption of photoredox cross-coupling reactions. The work described herein has culminated in robust photocatalysis and cross-coupling capabilities which are viewed as key platforms for medicinal chemistry research at AbbVie.

Combination of ensemble machine learning models in photocatalytic studies using nano TiO2 - Lignin based biochar

Synergizing photocatalytic reactions with machine learning methods can effectively optimize and automate the remediation of pollutants. In this work, commercial Degussa TiO2 nanoparticles and lignin based biochar (LB) where used to prepare TiO2: lignin based biochar (TLB) composites using ultrasound-assisted co-precipitation method. The photocatalytic property of the TLB composites where studied by conducting the photocatalytic degradation of a Basic blue 41 (BB41) dye. The influence of calcination temperature, T:LB compositions, catalyst dosage, initial dye pH, initial dye concentration, and illumination time on photocatalytic dye degradation were experimentally studied. The degradation efficiency of 96.72 % was obtained under optimized conditions for the photocatalyst calcined at 500 °C containing a 1:1 wt percentage of TiO2 and LB. The experimental data was further used to predict the photocatalytic degradation efficiency using Gradient Tree Boosting (GTB) and Extra Trees (ET) models. The GTB model gave the highest prediction accuracy of 94 %. The permutation variable importance revealed catalyst dosage and dye concentration as the most influential parameters in the prediction of the photocatalytic dye degradation efficiency.

Twisted Intramolecular Charge-Transfer State Addition to Electron-Poor Olefins

When electron-rich arylpyrrolinium salts are irradiated with ultraviolet light in the presence of Michael acceptors, the pyrrolinyl and aryl fragments add to the activated and polarized double bond in a regioselective manner, forming two C-C bonds and fragmenting the substrate. In this paper, we present a model for this intriguing reaction, supported by spectroscopy and computational analyses, and provide evidence for rectifying previously misassigned structures. We postulate that the photochemical reaction is inefficient because the reaction between the twisted intramolecular charge-transfer state and the olefin competes with fluorescence from this state upon photon absorption. We also discuss the practical advantages of performing this photochemical reaction in a continuous flow setup. Additionally, we explore several subsequent reactions that allow us to further modify the products of the photochemical step, ultimately leading to the creation of new chemical structures.

Recent advances and perspectives in solar photothermal conversion and storage systems: A review

Developing high-efficiency solar photothermal conversion and storage (SPCS) technology is significant in solving the imbalance between the supply and demand of solar energy utilization in time and space. Aiming at the current research status in the field of SPCS, this review thoroughly examines the phase change materials and substrates in SPCS systems. It elucidates the design principles and methods of SPCS integrated composites. Comparatively, it analyzes the parameters of various types of SPCS composites in terms of photothermal conversion, thermal conductivity, energy density, and cycling stability. Additionally, the review discusses the trade-offs between each parameter to achieve the most optimal effect of SPCS. By sorting out the current status of the application of SPCS technology in solar thermal/photovoltaic, aerospace, buildings, textile, and other industries, this analysis clarifies the requirements for various latent heat, phase change temperature, and other properties under different environmental conditions. Through a comprehensive discussion of SPCS technology, this paper accurately captures the development trend of efficiently and comprehensively utilizing solar energy by analyzing existing scientific problems. It identifies bottlenecks in SPCS technology and suggests future development directions that need focused attention. The insights gained from this analysis may provide a theoretical basis for designing strategies, enhancing performance, and promoting the application of SPCS.

Solar-Driven Continuous CO2 Reduction to CO and CH4 using Heterogeneous Photothermal Catalysts: Recent Progress and Remaining Challenges

The urgent need to reduce the carbon dioxide level in the atmosphere and keep the effects of climate change manageable has brought the concept of carbon capture and utilization to the forefront of scientific research. Amongst the promising pathways for this conversion, sunlight-powered photothermal processes, synergistically using both thermal and non-thermal effects of light, have gained significant attention. Research in this field focuses both on the development of catalysts and continuous-flow photoreactors, which offer significant advantages over batch reactors, particularly for scale-up. Here, we focus on sunlight-driven photothermal conversion of CO2 to chemical feedstock CO and CH4 as synthetic fuel. This review provides an overview of the recent progress in the development of photothermal catalysts and continuous-flow photoreactors and outlines the remaining challenges in these areas. Furthermore, it provides insight in additional components required to complete photothermal reaction systems for continuous production (e. g., solar concentrators, sensors and artificial light sources). In addition, our review emphasizes the necessity of integrated collaboration between different research areas, like chemistry, material science, chemical engineering, and optics, to establish optimized systems and reach the full potential of this technology.

Synthesis of the MN Ring of Caribbean Ciguatoxin C-CTX-1 via Desymmetrization by Acetal Formation

The MN ring of Caribbean ciguatoxin C-CTX-1 was synthesized from a meso-syn-2,7-dimethyloxepane derivative corresponding to the M ring via desymmetrization by acetal formation with a camphor derivative, followed by construction of the N ring via the Horner-Wadsworth-Emmons reaction and acetal formation. The meso-syn-2,7-dimethyloxepane derivative was synthesized via photoinduced electrocyclization of a conjugated exo-diene under flow conditions, giving a cyclobutene derivative, followed by ring expansion via oxidative cleavage and diastereoselective reduction of a β-hydroxy ketone.

Automated self-optimization, intensification, and scale-up of photocatalysis in flow

The optimization, intensification, and scale-up of photochemical processes constitute a particular challenge in a manufacturing environment geared primarily toward thermal chemistry. In this work, we present a versatile flow-based robotic platform to address these challenges through the integration of readily available hardware and custom software. Our open-source platform combines a liquid handler, syringe pumps, a tunable continuous-flow photoreactor, inexpensive Internet of Things devices, and an in-line benchtop nuclear magnetic resonance spectrometer to enable automated, data-rich optimization with a closed-loop Bayesian optimization strategy. A user-friendly graphical interface allows chemists without programming or machine learning expertise to easily monitor, analyze, and improve photocatalytic reactions with respect to both continuous and discrete variables. The system's effectiveness was demonstrated by increasing overall reaction yields and improving space-time yields compared with those of previously reported processes.

Radical Reactions in Organic Synthesis: Exploring in-, on-, and with-Water Methods

Radical reactions in water or aqueous media are important for organic synthesis, realizing high-yielding processes under non-toxic and environmentally friendly conditions. This overview includes (i) a general introduction to organic chemistry in water and aqueous media, (ii) synthetic approaches in, on, and with water as well as in heterogeneous phases, (iii) reactions of carbon-centered radicals with water (or deuterium oxide) activated through coordination with various Lewis acids, (iv) photocatalysis in water and aqueous media, and (v) synthetic applications bioinspired by naturally occurring processes. A wide range of chemical processes and synthetic strategies under different experimental conditions have been reviewed that lead to important functional group translocation and transformation reactions, leading to the preparation of complex molecules. These results reveal how water as a solvent/medium/reagent in radical chemistry has matured over the last two decades, with further discoveries anticipated in the near future.

Flowmicro In-Line Analysis-Driven Design of Reactions mediated by Unstable Intermediates: Flash Monitoring Approach

The direct observation of reactive intermediates is an important issue for organic synthesis. However, intermediates with an extreme instability are hard to be monitored by common spectroscopic methods such as FTIR. We have developed synthetic method utilizing flow microreactors, which enables a generation and reactions of unstable intermediates. Herein we report that, based on our flowmicro techniques, we developed an in-line analysis method for reactive intermediates in increments of milliseconds. We demonstrated the direct observation of the living and dead species of the anionic polymerization of alkyl methacrylates. The direct information of the living species enabled the anionic polymerization and copolymerization of oligo(ethylene glycol) methyl ether methacrylates, which is the important but difficult reaction in the conventional method.

Emerging environmentally friendly bio-based nanocomposites for the efficient removal of dyes and micropollutants from wastewater by adsorption: a comprehensive review

Water scarcity will worsen due to population growth, urbanization, and climate change. Addressing this issue requires developing energy-efficient and cost-effective water purification technologies. One approach is to use biomass to make bio-based materials (BBMs) with valuable attributes. This aligns with the goal of environmental conservation and waste management. Furthermore, the use of biomass is advantageous because it is readily available, economical, and has minimal secondary environmental impact. Biomass materials are ideal for water purification because they are abundant and contain important functional groups like hydroxyl, carboxyl, and amino groups. Functional groups are important for modifying and absorbing contaminants in water. Single-sourced biomass has limitations such as weak mechanical strength, limited adsorption capacity, and chemical instability. Investing in research and development is crucial for the development of efficient methods to produce BBMs and establish suitable water purification application models. This review covers BBM production, modification, functionalization, and their applications in wastewater treatment. These applications include oil-water separation, membrane filtration, micropollutant removal, and organic pollutant elimination. This review explores the production processes and properties of BBMs from biopolymers, highlighting their potential for water treatment applications. Furthermore, this review discusses the future prospects and challenges of developing BBMs for water treatment and usage. Finally, this review highlights the importance of BBMs in solving water purification challenges and encourages innovative solutions in this field.

Continuous Flow Synthesis of Nitrosoarenes via Photochemical Rearrangement of Aryl Imines

Nitrosoarenes are versatile organic building blocks; however, their intrinsic instability and limited synthetic accessibility have so far restricted their widespread use. Herein, we present a new continuous flow route toward these entities that is based on a direct photochemical rearrangement process using o-nitrophenylimines as starting materials. Due to the underlying redox mechanism, a new amide group accompanies the formation of the nitroso group. Crucial to the success of this approach is the use of trifluoroethanol as a solvent and high-power light-emitting diodes (365 nm) as light sources that provide uniform irradiation and high efficiency of the resulting continuous flow method. The process is fast and robust, with high functional group tolerance and high throughput. The formation of the nitroso moiety is supported by full spectroscopic analysis, including X-ray crystallography. The scalability of this flow approach allows access to gram quantities of nitroso species for which we highlight a small set of derivatization reactions underlining their synthetic utility.

Accelerated Electrophotocatalytic C(sp3 )-H Heteroarylation Enabled by an Efficient Continuous-Flow Reactor

Electrophotocatalytic transformations are garnering attention in organic synthesis, particularly for accessing reactive intermediates under mild conditions. Moving these methodologies to continuous-flow systems, or flow ElectroPhotoCatalysis (f-EPC), showcases potential for scalable processes due to enhanced irradiation, increased electrode surface, and improved mixing of the reaction mixture. Traditional methods sequentially link photochemical and electrochemical reactions, using flow reactors connected in series, yet struggle to accommodate reactive transient species. In this study, we introduce a new flow reactor concept for electrophotocatalysis (EPC) that simultaneously utilizes photons and electrons. The reactor is designed with a transparent electrode and employs cost-effective materials. We used this technology to develop an efficient process for electrophotocatalytic heteroarylation of C(sp3 )-H bonds. Importantly, the same setup can also facilitate purely electrochemical and photochemical transformations. This reactor represents a significant advancement in electrophotocatalysis, providing a framework for its application in flow for complex synthetic transformations.

Fluorescence to measure light intensity

Despite the need for quantitative measurements of light intensity across many scientific disciplines, existing technologies for measuring light dose at the sample of a fluorescence microscope cannot simultaneously retrieve light intensity along with spatial distribution over a wide range of wavelengths and intensities. To address this limitation, we developed two rapid and straightforward protocols that use organic dyes and fluorescent proteins as actinometers. The first protocol relies on molecular systems whose fluorescence intensity decays and/or rises in a monoexponential fashion when constant light is applied. The second protocol relies on a broad-absorbing photochemically inert fluorophore to back-calculate the light intensity from one wavelength to another. As a demonstration of their use, the protocols are applied to quantitatively characterize the spatial distribution of light of various fluorescence imaging systems, and to calibrate illumination of commercially available instruments and light sources.

Photoinduced [3+2] Cycloaddition of Carbenes and Nitriles: A Versatile Approach to Oxazole Synthesis

We have developed a photoinduced protocol for the synthesis of pharmaceutically important oxazole molecules using diazo- and nitrile-containing reactants. The process involves the initial photolysis of the diazo compound to afford singlet carbenes, which are tapped by nitriles in a [3+2] cycloaddition fashion to give substituted oxazoles. With di-nitrile compounds, useful bis-oxazoles were obtained. The applicability of the transformation is showcased through the expedient synthesis of small-molecule drugs and biologically relevant molecules such as felbinac, pimprinine, texamine, ugnenenazole etc. The protocol is also useful for the generation of 2 H and 13 C isotope labelled oxazoles. Merging photolysis with continuous-flow chemistry was demonstrated for scaling up the reaction. The non-requirement of metal catalysis or photosensitizers to harness the light energy with blue light sufficing the execution of the reaction makes it a versatile and general protocol for the synthesis of structurally diverse oxazoles.

Photochemical halogen-bonding assisted carbothiophosphorylation reactions of alkenyl and 1,3-dienyl bromides

Herein, we present a synthetic procedure for the facile and general preparation of novel S-alkenyl and dienyl phosphoro(di)thioates for the first time. Extensive mechanistic investigations support that the reactions rely on a photochemical excitation of a halogen-bonding complex, formed with a phosphorothioate salt and an alkenyl or dienyl bromide, which light-induced fragmentation leads to the formation of the desired products through a radical-based pathway. The substrate scope is broad and exhibits a wide functional group tolerance in the formation of the final compounds, including molecules derived from natural products, all with unknown and potentially interesting biological properties. Eventually, a very efficient continuous flow protocol was developed for the upscale of these reactions.

Photoreduction of Anthracenes Catalyzed by peri-Xanthenoxanthene: a Scalable and Sustainable Birch-Type Alternative

The typical Birch reduction transforms arenes into cyclohexa-1,4-dienes by using alkali metals, an alcohol as a proton source, and an amine as solvent. Capitalizing on the strong photoreductive properties of peri-xanthenoxanthene (PXX), herein we report the photocatalyzed "Birch-type" reduction of acenes by employing visible blue light irradiation at room temperature in the presence of air. Upon excitation at 405 or 460 nm in the presence of a mixture of N,N-diisopropylethylamine (DIPEA) and trifluoromethanesulfonimide (HNTf2 ) in DMSO, PXX photocatalyzes the selective reduction of full-carbon acene derivatives (24-75 %). Immobilization of PXX onto polydimethylsiloxane (PDMS) beads (PXX-PDMS) allowed the use of the catalyst in heterogeneous batch reactions, giving 9-phenyl-9,10-dihydroanthracene in high yield (68 %). The catalyst could easily be recovered and reused, with no notable drop in performance observed after five reaction cycles. Integration of the PXX-PDMS beads into a microreactor enabled the reduction of acenes under continuous-flow conditions, thereby validating the sustainability and scalability of this heterogeneous-phase approach.

Highly Scalable and Inherently Safer Preparation of Di, Tri and Tetra Nitrate Esters Using Continuous Flow Chemistry

Nitrate esters are important organic compounds having wide application in energetic materials, medicines and fuel additives. They are synthesized through nitration of aliphatic polyols. But the process safety challenges associated with nitration reaction makes the production process complicated and economically unviable. Herein, we have developed a continuous flow process wherein polyol and nitric acid are reacted in a microreactor to produce nitrate ester continuously. Our developed process is inherently safer and efficient. The process was optimized for industrially important nitrate esters containing two, three and four nitro groups. Substrates include glycol dinitrates: 1,2-propylene glycol dinitrate (PGDN), ethylene glycol dinitrate (EGDN), diethylene glycol dinitrate (DEGDN), triethylene glycol dinitrate (TEGDN); trinitrates: trimethylolethane trinitrate (TMETN), 1,2,4-butanetriol trinitrate (BTTN); and tetranitrates: erythritol tetranitrate (ETN). The optimized process for each molecule provided yield >90 % in a short residence time of 1 min corresponding to a space time yield of >18 g/h/mL of reactor volume.

Advances in Continuous Flow Fluorination Reactions

Fluorination reactions are important in constructing organofluorine motifs, which contribute to favorable biological properties in pharmaceuticals and agrochemicals. However, fluorination reagents and reactions are associated with various problems, such as their hazardous nature, high exothermicity, and poor selectivity and scalability. Continuous flow has emerged as a transformative technology to provide many advantages relative to batch syntheses. This review article summarizes recent continuous flow techniques that address the limitations and challenges of fluorination reactions. Approaches based on different flow techniques are discussed, including gas-liquid reactions, packed-bed reactors, in-line purifications, streamlined multistep synthesis, large-scale reactions well as flow photoredox- and electrocatalysis.

Near-Infrared Light-Induced Reversible Deactivation Radical Polymerization: Expanding Frontiers in Photopolymerization

Photoinduced reversible deactivation radical polymerization (photo-RDRP) or photoinduced controlled/living radical polymerization has emerged as a versatile and powerful technique for preparing functional and advanced polymer materials under mild conditions by harnessing light energy. While UV and visible light (λ = 400-700 nm) are extensively employed in photo-RDRP, the utilization of near-infrared (NIR) wavelengths (λ = 700-2500 nm) beyond the visible region remains relatively unexplored. NIR light possesses unique properties, including enhanced light penetration, reduced light scattering, and low biomolecule absorption, thereby providing opportunities for applying photo-RDRP in the fields of manufacturing and medicine. This comprehensive review categorizes all known NIR light-induced RDRP (NIR-RDRP) systems into four mechanism-based types: mediation by upconversion nanoparticles, mediation by photocatalysts, photothermal conversion, and two-photon absorption. The distinct photoinitiation pathways associated with each mechanism are discussed. Furthermore, this review highlights the diverse applications of NIR-RDRP reported to date, including 3D printing, polymer brush fabrication, drug delivery, nanoparticle synthesis, and hydrogel formation. By presenting these applications, the review underscores the exceptional capabilities of NIR-RDRP and offers guidance for developing high-performance and versatile photopolymerization systems. Exploiting the unique properties of NIR light unlocks new opportunities for synthesizing functional and advanced polymer materials.

Superhydrophobic Tipped Antimicrobial Photodynamic Therapy Device for the In Vivo Treatment of Periodontitis Using a Wistar Rat Model

Limited options exist for treatment of periodontitis; scaling and root planing (SRP) are not sufficient to eradicate P. gingivalis and the resulting inflammatory disease. Chlorhexidine (CHX), used as an adjuvant to SRP, may reduce bacterial loads but leads to pain and staining, while evidence for its efficacy is lacking. Antibiotics are effective but can lead to drug-resistance. The rising concern of antibiotic resistance limits the future use of this treatment approach. This study evaluates the efficacy of a novel superhydrophobic (SH) antimicrobial photodynamic therapy (aPDT) device as an adjuvant to SRP for the treatment of periodontitis induced in a Wistar rat in vivo model relative to CHX. The SH-aPDT device comprises an SH silicone rubber strip coated with verteporfin photosensitizer (PS), sterilized, and secured onto a tapered plastic optical fiber tip connected to a red diode laser. The superhydrophobic polydimethylsiloxane (PDMS) strips were fabricated by using a novel soluble template method that creates a medical-grade elastomer with hierarchical surface roughness without the use of nanoparticles. Superhydrophobicity minimizes direct contact of the PS-coated surface with bacterial biofilms. Upon insertion of the device tip into the pocket and energizing the laser, the device generates singlet oxygen that effectively targets and eliminates bacteria within the periodontal pocket. SH-aPDT treatment using 125 J/cm2 of red light on three consecutive days reduced P. gingivalis significantly more than SRP-CHX controls (p < 0.05). Clinical parameters significantly improved (p < 0.05), and histology and stereometry results demonstrated SH-aPDT to be the most effective treatment for improving healing and reducing inflammation, with an increase in fibroblast cells and extracellular matrix and a reduction in vascularization, inflammatory cells, and COX-2 expression. The SH-aPDT approach resulted in complete disease clearance assessed 30 days after treatment initiation with significant reduction of the periodontal pocket and re-formation of the junctional epithelium at the enamel-cementum junction. PS isolation on a SH strip minimizes the potential for bacteria to develop resistance, where the treatment may be aided by the oxygen supply retained within the SH surface.

Photoinduced Efficient Catalytic α-Alkylation Reactions of Active Methylene and Methine Compounds with Nonactivated Alkenes

In catalytic α-alkylation reactions of carbonyl compounds, although SN2-type substitution reactions of enolates with alkyl halides are a conventional methodology, addition reactions with alkenes are more desirable because of their atom-economical character; however, reactions with nonactivated alkenes are challenging. Here, we developed highly efficient catalytic α-alkylation reactions of active methylene and methine compounds with nonactivated alkenes such as 1-decene using an organophotocatalyst and lithium thiophenoxide as a Lewis acid/Brønsted base/hydrogen atom transfer (HAT) multifunctional catalyst under blue-light irradiation. The reaction was also performed with a higher degree of efficiency under a continuous-flow system to obtain the products in multigram scales. The present reaction system enables highly efficient and practical α-alkylation reactions of active methylene and methine compounds to be achieved.

Developing Amphetamine Certified Reference Materials: From Batch and Continuous-Flow Synthesis to Certification Protocol

Certified reference materials (CRM) of amphetamine derivatives were produced through a simple, rapid and efficient synthesis in both batch and continuous-flow conditions, accompanied by the development of a comprehensive certification protocol for this class of substances. Our chemistry enabled the synthesis of MDA, MDMA, PMA and PMMA in two steps from safrole and estragole with overall yields of 38-61 % in 48 hours under batch conditions and 61-65 % in 65 minutes under continuous-flow conditions, followed by the development of a certification protocol for these materials through identity checking, homogeneity, stability, and characterization studies. Furthermore, as result of this work, a very pure CRM of MDA.HCl with 99.1±1.4 g/100 g of certified characterization value was produced. Considering the importance of supplying amphetamine calibrants for public security efforts in Forensic Chemistry, the potential therapeutical applications, and responding to the rising demand for the synthesis of CRM, this work presents a pioneering approach for the production of amphetamine and related compounds.

The Photochemical Mediated Ring Contraction of 4H-1,2,6-Thiadiazines To Afford 1,2,5-Thiadiazol-3(2H)-one 1-Oxides

1,2,6-Thiadiazines treated with visible light and 3O2 under ambient conditions are converted into difficult-to-access 1,2,5-thiadiazole 1-oxides (35 examples, yields of 39-100%). Experimental and theoretical studies reveal that 1,2,6-thiadiazines act as triplet photosensitizers that produce 1O2 and then undergo a chemoselective [3 + 2] cycloaddition to give an endoperoxide that ring contracts with selective carbon atom excision and complete atom economy. The reaction was optimized under both batch and continuous-flow conditions and is also efficient in green solvents.

High Throughput Multidimensional Kinetic Screening in Continuous Flow Reactors

An automated high throughput multidimensional reaction screening platform based on an inline Fourier-transform infrared spectroscopy is presented. By combining flow chemistry, machine automation and inline analysis, the platform is able to screen reactions in multidimensions (residence time, monomer concentration, degree of polymerization, reaction temperature and monomer conversion) rapidly and efficiently way. Kinetic data libraries associated with high data precision (absolute error <4 %), high reproducibility and high data density are built with ease from the platform. To test the method, we screened the reversible addition-fragmentation chain transfer polymerization of methyl acrylate in unmatched detail, and the ring opening metathesis polymerization of methyl-5-norbornene-2-carboxylate. The method we introduce is a key step in providing "big data" for data driven research in the future, and already at present allows for precise prediction of reaction outcomes within the high-dimensional chemical parameter space that is screened.

Photoinduced Nitroarenes as Versatile Anaerobic Oxidants for Accessing Carbonyl and Imine Derivatives

Herein, we report a protocol for the anaerobic oxidation of alcohols, amines, aldehydes, and imines promoted by photoexcited nitroarenes. Mechanistic studies support the idea that photoexcited nitroarenes undergo double hydrogen atom transfer (HAT) steps with alcohols and amines to provide the respective ketone and imine products. In the presence of aldehydes and imines, successive HAT and oxygen atom transfer (OAT) events occur to yield carboxylic acids and amides, respectively. This transformation is amenable to a continuous-photoflow setup, which led to reduced reaction times.

Fluoroalkyl Sulfoximines for Versatile Photocatalytic Radical Fluoroalkylations

Fluoroalkyl sulfoximines, which serve as electron-accepting fluoroalkyl radical sources, are easy-to-handle, solid, and bench-stable chemicals. Fluoroalkyl radicals can be generated from sulfoximine reagents using strong one-electron injectors, such as a highly reducing photoredox catalyst in the excited state. Our group has developed photocatalytic radical di- and mono-fluoromethylation and α-monofluoroalkylation of olefins with the corresponding fluoroalkyl sulfoximines. In this personal account, appropriate combinations of fluoroalkyl sulfoximines and photoredox catalysts, leading to successful radical fluoroalkylation, have been discussed.

Current State of Microflow Trifluoromethylation Reactions

The trifluoromethyl group is a powerful structural motif in drugs and polymers; thus, developing trifluoromethylation reactions is an important area of research in organic chemistry. Over the past few decades, significant progress has been made in developing new methods for the trifluoromethylation of organic molecules, ranging from nucleophilic and electrophilic approaches to transition-metal catalysis, photocatalysis, and electrolytic reactions. While these reactions were initially developed in batch systems, more recent microflow versions are highly attractive for industrial applications owing to their scalability, safety, and time efficiency. In this review, we discuss the current state of microflow trifluoromethylation. Approaches for microflow trifluoromethylation based on different trifluoromethylation reagents are described, including continuous flow, flow photochemical, microfluidic electrochemical reactions, and large-scale microflow reactions.

Customized Production of Holey Graphene Oxides via a Continuous Flow Process

Continuous flow manufacturing is an innovative technology mainly applied in the chemical and pharmaceutical industries that is progressively being adapted to the manufacturing of nanomaterials to overcome the challenge of reproducing a product with consistent characteristics at a large scale. Here, a flow photochemical system is designed and prototyped for the synthesis of holey graphene oxides (hGOs). Compared to existing methods for the synthesis of hGO, the process is fast, highly scalable, and controllable. Through a combination of rigorous data analysis using machine learning algorithms on transmission electron microscope images and systematic studies of process parameters, it is demonstrated that characteristics of the produced hGO (i.e., porosity and pore size) are remarkably reproducible to the extent that it can be predicted by empirical models of processing-property correlations. Depending on the tailored nanopore structures, the synthesized hGOs out-performed GO in a range of applications that can benefit from the nanoporous two-dimensional (2D) sheets such as in supercapacitors, gas adsorption, and nanofiltration membranes. These results are significant in offering new perspectives on the low-cost industrialization of 2D nanomaterials.

External Flash Generation of Carbenoids Enables Monodeuteration of Dihalomethanes

In this study, incorporation of one deuterium atom was achieved by H-D exchange of one of the two identical methylene protons in various dihalomethanes (halogen=Cl, Br, and I) through a rapid-mixing microflow reaction of lithium diisopropylamide as a strong base and deuterated methanol as a deuteration reagent. Generation of highly unstable carbenoid intermediate and suppression of its decomposition were successfully controlled under high flow-rate conditions. Monofunctionalization of diiodomethane afforded various building blocks composed of boryl, stannyl, and silyl groups. The monodeuterated diiodomethane, which served as a deuterated C1 source, was subsequently subjected to diverted functionalization methods to afford various products including biologically important molecules bearing isotope labelling at specific positions and homologation products with monodeuteration.

Metal-Free Addition of Alkyl Bromides to Access 3,3-Disubstituted Quinoxalinones Enabled by Visible-Light Photoredox Catalysis

A metal-free addition of unactivated alkyl bromides to quinoxalin-2(1H)-ones is described. This method enables the construction of valuable 3,3-disubstituted dihydroquinoxalin-2(1H)-ones bearing quaternary carbon centers under mild, visible-light photoredox catalysis. High functional group tolerance is observed in both the quinoxalinone and alkyl bromide partners. The ability to scale up this method was demonstrated under photo-flow conditions to enable gram-scale synthesis.

Microparticle Manipulation Performed on a Swirl-Based Microfluidic Chip Featured by Dual-Stagnation Points

Stagnation-based microfluidics technology is promising for microparticle control due to its noncontact and low cost. However, the current research is still hindered by insufficient pose regulating ability and soft control. Based on our previous work on controlling single particles by generating a swirling flow region (SFR) with a stagnation point in the designed flow field, a new 3-microchannel structure is herein proposed for simultaneous control of two microparticles. It is addressed as the dual-stagnation model because there are two SFRs generated for particle capturing and manipulation. Simulation study is conducted to optimize the fluid field structure and explore the regulation of the two SFRs by adjusting velocities of microchannel inlets. Experiments are carried out on a 3D-printed microfluidic chip to validate the feasibility of the dual-stagnation model and the predicting capacity of the simulations. It is demonstrated that two SFRs with stagnation points are successfully formed in specific locations, indicating that two microparticles can be concurrently captured and controlled. Significantly, the results of simulation and experimental studies agree well with each other referring to flow streamlines and stagnation point regulation. During experiments, it is confirmed that microparticles with different shapes and varied sizes can be captured. Besides, the deviation between the positions of microparticles and the generated stagnation points is characterized to reveal the trapping stability of this microfluidic chip. This work contributes to an advanced flow field structure for swirl-based microfluidic chips and provides insights into soft contact and flexible manipulation of multiple microparticles for revealing the interaction between two bio-/chemical microparticles.