Pt(II)/Pd(II)-Based Metallosupramolecular Architectures as Light Harvesting Systems and their Applications

The development of artificial light-harvesting systems mimicking the natural photosynthesis method is an ever-growing field of research. Numerous systems such as polymers, metal complexes, POFs, COFs, supramolecular frameworks etc. have been fabricated to accomplish more efficient energy transfer and storage. Among them, the supramolecular coordination complexes (SCCs) formed by non-covalent metal-ligand interaction, have shown the capacity to not only undergo single and multistep energy migration but also to utilize the harvested energy for a wide variety of applications such as photocatalysis, tunable emissive systems, encrypted anti-counterfeiting materials, white light emitters etc. This review sheds light on the light-harvesting behavior of both the 2D metallacycles and 3D metallacages where design ingenuity has been executed to afford energy harvesting by both donor ligands as well as metal acceptors.

Photocatalysts for a sustainable future: Innovations in large-scale environmental and energy applications

The growing environmental and energy crises have prompted researchers to seek new solutions, including large-scale photocatalytic environmental remediation and the production of solar hydrogen using photocatalytic materials. To achieve this goal, scientists have developed numerous photocatalysts with high efficiency and stability. However, the large-scale application of photocatalytic systems under real-world conditions is still limited. These limitations arise at every step, including the large-scale synthesis and deposition of photocatalyst particles on a solid support, and the development of an optimal design with high mass transfer and efficient photon absorption. The purpose of this article is to provide a detailed description of the primary challenges and potential solutions encountered in scaling up photocatalytic systems for use in large-scale water and air purification and solar hydrogen production. Additionally, based on a review of current pilot developments, we draw conclusions and make comparisons regarding the main operating parameters that affect performance, as well as propose strategies for future research.

Quid Pro Flow

How do you get into flow? We trained in flow chemistry during postdoctoral research and are now applying it in new areas: materials chemistry, crystallization, and supramolecular synthesis. Typically, when researchers think of "flow", they are considering predominantly liquid-based organic synthesis; application to other disciplines comes with its own challenges. In this Perspective, we highlight why we use and champion flow technologies in our fields, summarize some of the questions we encounter when discussing entry into flow research, and suggest steps to make the transition into the field, emphasizing that communication and collaboration between disciplines is key.

A 3D Printer in the Lab: Not Only a Toy

Although 3D printers are becoming more common in households, they are still under-represented in many laboratories worldwide and regarded as toys rather than as laboratory equipment. This short review wants to change this conservative point of view. This mini-review focuses on fused deposition modeling printers and what happens after acquiring your first 3D printer. In short, these printers melt plastic filament and deposit it layer by layer to create the final object. They are getting cheaper and easier to use, and nowadays it is not difficult to find good 3D printers for less than €500. At such a price, a 3D printer is one, if not the most, versatile piece of equipment you can have in a laboratory.

Rapid and Replaceable Luminescent Coating for Silicon-Based Microreactors Enabling Energy-Efficient Solar Photochemistry

The sun is the most sustainable source of photons on the earth but is rarely used in photochemical transformations due its relatively low and variable intensity, broad wavelength range, and lack of focus. Luminescent solar concentrator-based photomicroreactors (LSC-PMs) can be an answer to all these issues, but widespread adoption is plagued by challenges associated with their complicated manufacturing. Herein, we developed a new strategy to accelerate and ease the production of LSC-PMs by depositing a thin luminescent film on commercially and widely available silicon-based microreactors. The protocol is fast and operationally simple, and the luminescent coating can be easily removed and replaced. This enables rapid tuning of the luminescent coating to fit the requirements of the photocatalytic system and to increase the photon flux inside the microreactor channels.

Förster Resonance Energy Transfer in Luminescent Solar Concentrators

Luminescent solar concentrators (LSCs) are an emerging technology to collect and channel light from a large absorption area into a smaller one. They are a complementary technology for traditional solar photovoltaics (PV), particularly suitable for application in urban or indoor environments where their custom colors and form factors, and performance under diffuse light conditions may be advantageous. Förster resonance energy transfer (FRET) has emerged as a valuable approach to overcome some of the intrinsic limitations of conventional single lumophore LSCs, such as reabsorption or reduced quantum efficiency. This review outlines the potential of FRET to boost LSC performance, using highlights from the literature to illustrate the key criteria that must be considered when designing an FRET-LSC, including both the photophysical requirements of the FRET lumophores and their interaction with the host material. Based on these criteria, a list of design guidelines intended to aid researchers when they approach the design of a new FRET-LSC system is presented. By highlighting the unanswered questions in this field, the authors aim to demonstrate the potential of FRET-LSCs for both conventional solar-harvesting and emerging LSC-inspired technologies and hope to encourage participation from a diverse researcher base to address this exciting challenge.

Plant-inspired TransfOrigami microfluidics

The healthy functioning of the plants' vasculature depends on their ability to respond to environmental changes. In contrast, synthetic microfluidic systems have rarely demonstrated this environmental responsiveness. Plants respond to environmental stimuli through nastic movement, which inspires us to introduce transformable microfluidics: By embedding stimuli-responsive materials, the microfluidic device can respond to temperature, humidity, and light irradiance. Furthermore, by designing a foldable geometry, these responsive movements can follow the preset origami transformation. We term this device TransfOrigami microfluidics (TOM) to highlight the close connection between its transformation and the origami structure. TOM can be used as an environmentally adaptive photomicroreactor. It senses the environmental stimuli and feeds them back positively into photosynthetic conversion through morphological transformation. The principle behind this morphable microsystem can potentially be extended to applications that require responsiveness between the environment and the devices, such as dynamic artificial vascular networks and shape-adaptive flexible electronics.

Technological Innovations in Photochemistry for Organic Synthesis: Flow Chemistry, High-Throughput Experimentation, Scale-up, and Photoelectrochemistry

Photoinduced chemical transformations have received in recent years a tremendous amount of attention, providing a plethora of opportunities to synthetic organic chemists. However, performing a photochemical transformation can be quite a challenge because of various issues related to the delivery of photons. These challenges have barred the widespread adoption of photochemical steps in the chemical industry. However, in the past decade, several technological innovations have led to more reproducible, selective, and scalable photoinduced reactions. Herein, we provide a comprehensive overview of these exciting technological advances, including flow chemistry, high-throughput experimentation, reactor design and scale-up, and the combination of photo- and electro-chemistry.

Development of an Off-Grid Solar-Powered Autonomous Chemical Mini-Plant for Producing Fine Chemicals

Photochemistry using inexhaustible solar energy is an eco-friendly way to produce fine chemicals outside the typical laboratory or chemical plant environment. However, variations in solar irradiation conditions and the need for an external energy source to power electronic components limits the accessibility of this approach. In this work, a chemical solar-driven "mini-plant" centred around a scaled-up luminescent solar concentrator photomicroreactor (LSC-PM) was built. To account for the variations in solar irradiance at ground level and passing clouds, a responsive control system was designed that rapidly adapts the flow rate of the reagents to the light received by the reaction channels. Supplying the plant with solar panels, integrated into the module by placing it behind the LSC to utilize the transmitted fraction of the solar irradiation, allowed this setup to be self-sufficient and fully operational off-grid. Such a system can shine in isolated environments and in a distributed manufacturing world, allowing to decentralize the production of fine chemicals.

The development of luminescent solar concentrator-based photomicroreactors: a cheap reactor enabling efficient solar-powered photochemistry

Sunlight strikes our planet every day with more energy than we consume in an entire year. Therefore, many researchers have explored ways to efficiently harvest and use sunlight energy for the activation of organic molecules. However, implementation of this energy source in the large-scale production of fine chemicals has been mostly neglected. The use of solar energy for chemical transformations suffers from potential drawbacks including scattering, reflections, cloud shading and poor matches between the solar emission and absorption characteristics of the photochemical reaction. In this account, we provide an overview of our efforts to overcome these issues through the development of Luminescent Solar Concentrator-based PhotoMicroreactors (LSC-PM). Such reactors can efficiently convert solar energy with a broad spectral distribution to concentrated and wavelength-shifted irradiation which matches the absorption maximum of the photocatalyst. Hence, the use of these conceptually new photomicroreactors provides an increased solar light harvesting capacity, enabling efficient solar-powered photochemistry.

Bodipy-Containing Porous Microcapsules for Flow Heterogeneous Photocatalysis

Photocatalysis is a facile strategy for complex chemical transformations. Heterogeneous photocatalysis, especially in the flow system, has attracted much attention as it avoids the separation of catalysts. Herein, a kind of a Bodipy-containing porous microcapsule heterogeneous photocatalyst was rationally constructed with modulation on a multiscale. The diiodo-Bodipy with methacrylate (MA-2IBDP) was synthesized as a polymerizable photosensitizer. After immobilization in a polymer matrix, the intersystem crossing rate constant of MA-2IBDP increased to 2.7 × 10¹⁰ s^-1 and its triplet excited-state lifetime prolonged to ∼1 ms. Porous structures in microcapsules were created to facilitate mass transfer. A flat plate flow reactor was constructed to fix the catalytic microcapsules and improve light utilization. With the combination of all the above benefits, the reaction rate constant (0.896 s^-1) is 10 times faster than that of MA-2IBDP in a homogeneous system for juglone synthesis. The continuous production can last for 30 h without yield decrease. The photocatalyst can also be used in aza-Henry reaction, Alder-Ene reaction, and oxidation of thiols to disulfides with conversion rates above 95%. This study provides a means for the construction of heterogeneous catalysts and the flow reaction system.

Prevent or Cure-The Unprecedented Need for Self-Reporting Materials

Self-reporting smart materials are highly relevant in modern soft matter materials science, as they allow for the autonomous detection of changes in synthetic polymers, materials, and composites. Despite critical advantages of such materials, for example, prolonged lifetime or prevention of disastrous material failures, they have gained much less attention than self-healing materials. However, as diagnosis is critical for any therapy, it is of the utmost importance to report the existence of system changes and their exact location to prevent them from spreading. Thus, we herein critically review the chemistry of self-reporting soft matter materials systems and highlight how current challenges and limitations may be overcome by successfully transferring self-reporting research concepts from the laboratory to the real world. Especially in the space of diagnostic self-reporting systems, the recent SARS-CoV-2 (COVID-19) pandemic indicates an urgent need for such concepts that may be able to detect the presence of viruses or bacteria on and within materials in a self-reporting fashion.

Rapid synchronized fabrication of vascularized thermosets and composites

Bioinspired vascular networks transport heat and mass in hydrogels, microfluidic devices, self-healing and self-cooling structures, filters, and flow batteries. Lengthy, multistep fabrication processes involving solvents, external heat, and vacuum hinder large-scale application of vascular networks in structural materials. Here, we report the rapid (seconds to minutes), scalable, and synchronized fabrication of vascular thermosets and fiber-reinforced composites under ambient conditions. The exothermic frontal polymerization (FP) of a liquid or gelled resin facilitates coordinated depolymerization of an embedded sacrificial template to create host structures with high-fidelity interconnected microchannels. The chemical energy released during matrix polymerization eliminates the need for a sustained external heat source and greatly reduces external energy consumption for processing. Programming the rate of depolymerization of the sacrificial thermoplastic to match the kinetics of FP has the potential to significantly expedite the fabrication of vascular structures with extended lifetimes, microreactors, and imaging phantoms for understanding capillary flow in biological systems.

Bioinspired vascular networks transport heat and mass in multifunctional materials but lengthy multistep fabrication processes hinder large-scale application of structural vascular materials. Here, the authors report rapid, scalable, and synchronized fabrication of vascular thermosets and fiberreinforced composites under ambient conditions.

Aerobic Oxidations in Asymmetric Synthesis: Catalytic Strategies and Recent Developments

Despite the remarkable advances in the area of asymmetric catalytic oxidations over the past decades, the development of sustainable and environmentally benign enantioselective oxidation techniques, especially with the efficiency level similar to natural enzymes, still represents a challenge. The growing demand for enantiopure compounds and high interest to industry-relevant green technological advances continue to encourage the research pursuits in this field. Among various oxidants, molecular oxygen is ubiquitous, being available at low cost, environmentally benign and easy-to-handle material. This review highlights recent achievements in catalytic enantioselective oxidations utilizing molecular oxygen as the sole oxidant, with focus on the mechanisms of dioxygen activation and chirogenesis in these transformations.

Emerging concepts in photocatalytic organic synthesis

Visible light photocatalysis has become a powerful tool in organic synthesis that uses photons as traceless, sustainable reagents. Most of the activities in the field focus on the development of new reactions via common photoredox cycles, but recently a number of exciting new concepts and strategies entered less charted territories. We survey approaches that enable the use of longer wavelengths and show that the wavelength and intensity of photons are import parameters that enable tuning of the reactivity of a photocatalyst to control or change the selectivity of chemical reactions. In addition, we discuss recent efforts to substitute strong reductants, such as elemental lithium and sodium, by light and technological advances in the field.

Toward the Scale-Up of a Bicyclic Homopiperazine via Schmidt Rearrangement and Photochemical Oxaziridine Rearrangement in Continuous-Flow

The scale-up of a chiral bicyclic homopiperazine of pharmaceutical interest was investigated. The outcome and safety profile of a key batch ring-expansion step via Schmidt rearrangement was improved using continuous-flow chemistry. The selectivity of nitrogen insertion for the ring expansion was improved via an alternative photochemical oxaziridine rearrangement under mild conditions, which when converted to continuous-flow in a simple and efficient flow reactor allowed the first photochemical scale-up of a homopiperazine.

Application of reactor engineering concepts in continuous flow chemistry: a review

The adoption of flow technology for the manufacture of chemical entities, and in particular pharmaceuticals, has seen rapid growth over the past two decades with the technology now blurring the lines between chemistry and chemical engineering.

Dawn of a new era in industrial photochemistry: the scale-up of micro- and mesostructured photoreactors

Photochemical activation routes are gaining the attention of the scientific community since they can offer an alternative to the traditional chemical industry that mainly utilizes thermochemical activation of molecules. Photoreactions are fast and selective, which would potentially reduce the downstream costs significantly if the process is optimized properly. With the transition towards green chemistry, the traditional batch photoreactor operation is becoming abundant in this field. Process intensification efforts led to micro- and mesostructured flow photoreactors. In this work, we are reviewing structured photoreactors by elaborating on the bottleneck of this field: the development of an efficient scale-up strategy. In line with this, micro- and mesostructured bench-scale photoreactors were evaluated based on a new benchmark called photochemical space time yield (mol·day⁻¹·kW⁻¹), which takes into account the energy efficiency of the photoreactors. It was manifested that along with the selection of the photoreactor dimensions and an appropriate light source, optimization of the process conditions, such as the residence time and the concentration of the photoactive molecule is also crucial for an efficient photoreactor operation. In this paper, we are aiming to give a comprehensive understanding for scale-up strategies by benchmarking selected photoreactors and by discussing transport phenomena in several other photoreactors.

Scale-up Design of a Fluorescent Fluid Photochemical Microreactor by 3D Printing

The integration of light-converting media and microflow chemistry renders new opportunities for high-efficient utilization of solar energy to drive chemical reactions. Recently, we proposed a design of fluorescent fluid photochemical microreactor (FFPM) with a separate light channel and reaction channel, which displays excellent advantages in energy efficiency, flexibility, and general use. However, the limitations of the scalability of the microchannel reactor are still a big challenge to be overcome. Herein, we illustrate the scalability of such an FFPM via a 2 ⁿ numbering-up strategy by 3D printing technology. Channel shape, number, and interchannel spacing have been optimized, and the serpentine FFPM shows the best scalability with an excellent conversion rate and massive throughput. Reactors with up to eight channels have been fabricated and displayed conversions comparable to that obtained in a single-channel reactor, which provides a feasible strategy and an optimized structure model for batch production of fine chemicals.

Dual Thermal-/Electrical-Responsive Luminescent ‘Smart’ Window

As buildings are a large energy user, it is important to not only reduce their consumption, but also have them generate their own electricity. Here, we describe a smart window that could reduce electricity consumption, normally used for air conditioning and lighting, by absorbing excess solar radiation with dichroic fluorescent dye molecules aligned in a switchable liquid crystal host and guiding the re-emitted light energy to the edges of the device, where it can be used to generate electricity via attached photovoltaic cells. The liquid crystals are responsive both to temperature changes and applied electrical fields. At higher temperatures, transmission decreases due to increased disorder in the liquid crystals, while the application of an electrical field increases transmission by effectively realigning the dyes for minimal absorption. Using alternative configurations, a window with a transparent rest state was also produced, in which transmission can be decreased by applying an electrical field; the thermal response remains identical.

Process analytical technology (PAT) as a versatile tool for real-time monitoring and kinetic evaluation of photocatalytic reactions

Combining in situ Raman spectroscopy with multivariate data analysis enables the real-time monitoring and kinetic evaluation of photocatalytic reactions. The applicability is demonstrated on the photooxidation of 4-methoxythiophenol.

Cloud-inspired multiple scattering for light intensified photochemical flow reactors

A novel photoflow reactor that mimics how nature accelerates photochemistry in the clouds.

Dual-responsive "smart" window and visually attractive coating based on a diarylethene photochromic dye

Controlling the intensity and manipulating the spectral composition of sunlight are critical for many devices including "smart" windows, greenhouses, and photomicroreactors, but these are also important in more decorative applications. Here, we use a diarylethene dye incorporated in a liquid crystal host to create a dual-responsive "smart" window regulated both by an electrical trigger and by specific wavelengths of light. By incorporating the same diarylethene dye in a polymerizable host and using inkjet printing, coatings can be made with complete freedom in the applied pattern design, although the electrical response is lost. The color change of the diarylethene dye can be controlled in simulated sunlight by concurrent light exposure from an LED source, allowing a manual override for outdoor use. Photoluminescence of the closed isomer of the diarylethene from the light guide edges could be used for lighting or electricity generation in a luminescent solar concentrator architecture.

Energy-Efficient Solar Photochemistry with Luminescent Solar Concentrator Based Photomicroreactors

The sun is the most sustainable light source available on our planet, therefore the direct use of sunlight for photochemistry is extremely appealing. Demonstrated here, for the first time, is that a diverse set of photon-driven transformations can be efficiently powered by solar irradiation with the use of solvent-resistant and cheap luminescent solar concentrator based photomicroreactors. Blue, green, and red reactors can accommodate both homogeneous and multiphase reaction conditions, including photochemical oxidations, photocatalytic trifluoromethylation chemistry, and metallaphotoredox transformations, thus spanning applications over the entire visible-light spectrum. To further illustrate the efficacy of these novel solar reactors, medicinally relevant molecules, such as ascaridole and an intermediate of artemisinin, were prepared as well.

Microreactors: ‘micro’managing our macro energy demands

Purpose

The purpose of this paper is to answer this question by discussing the practicality of implementing microreactor technology towards large-scale renewable energy generation, as well as provide an incentive for future researchers to utilize microreactors as a useful alternative tool for green energy production. However, can microreactors present a viable solution for the generation of renewable energy to tackle the on-going global energy crisis?

Design/methodology/approach

In this paper, the practicality of implementing microreactor technology toward large-scale renewable energy generation is discussed. Specific areas of interest that elucidate considerable returns of microreactors toward renewable energy production are biofuel synthesis, hydrogen conversion and solar energy harvesting.

Findings

It is believed that sustained research on microreactors can significantly accelerate the development of new energy production methods through renewable sources, which will undoubtedly aid in the quest for a greener future.

Originality/value

This work aims to provide a sound judgement on the importance of research on renewable energy production and alternative energy management methods through microreactor technology, and why future studies on this topic should be highly encouraged. The relevance of this opinion paper lies in the idea that microreactors are an innovative concept currently used in engineering to significantly accelerate chemical reactions on microscale volumes; with the feasibility of high throughput to convert energy at larger scales with much greater efficiency than existing energy production methods.

Structural Transformation in Metal-Organic Frameworks for Reversible Binding of Oxygen

Polycyclic aromatic derivatives can trap ¹ O₂ to form endoperoxides (EPOs) for O₂ storage and as sources of reactive oxygen species. However, these materials suffer from structural amorphism, which limit both practical applications and fundamental studies on their structural optimization for O₂ capture and release. Metal-organic frameworks (MOFs) offer advantages in O₂ binding, such as clear structure-performance relationships and precise controllability. Herein, we report the reversible binding of O₂ is realized via the chemical transformation between anthracene-based and the corresponding EPO-based MOF. It is shown that anthracene-based MOF, the framework featuring linkers with polycyclic aromatic structure, can rapidly trap ¹ O₂ to form EPOs and can be restored upon UV irradiation or heating to release O₂ . Furthermore, we confirm that photosensitizer-incorporated anthracene-based MOF are promising candidates for reversible O₂ carriers controlled by switching Vis/UV irradiation.

Light as a reaction parameter – systematic wavelength screening in photochemical synthesis

Systematic wavelength screening with 16 LED arrays in a continuous-flow photoreactor revealed different reaction channels for the perfluoroalkylation of 2-methylindole, which were transferred into independent synthetic routes.

Design and application of a modular and scalable electrochemical flow microreactor

Electrochemistry constitutes a mild, green and versatile activation method of organic molecules. Despite these innate advantages, its widespread use in organic chemistry has been hampered due to technical limitations, such as mass and heat transfer limitations which restraints the scalability of electrochemical methods. Herein, we describe an undivided-cell electrochemical flow reactor with a flexible reactor volume. This enables its use in two different modes, which are highly relevant for flow chemistry applications, including a serial (volume ranging from 88 μL/channel up to 704 μL) or a parallel mode (numbering-up). The electrochemical flow reactor was subsequently assessed in two synthetic transformations, which confirms its versatility and scale-up potential.

Solar Photochemistry in Flow

In recent years, photochemistry has been a highly active research field. This renaissance is linked to the upsurge of photoredox catalysis, a versatile platform for synthetic methodologies using visible light photons as a traceless reagent. In contrast with UV, visible light constitutes almost half of the ground solar irradiance, making the use of solar light in chemistry a sustainable and viable possibility. However, the direct use of sunlight to power chemical reactions is still little explored. This can be explained by both the hurdles associated with solar radiation (e.g., its variability, irreproducibility, high IR content, etc.) and the need for a specialized photoreactor. Most of these issues can be tackled with technological solutions, and especially with the recourse to flow chemistry. Flow chemistry goes hand in hand with photochemistry thanks to the uniform irradiation it provides to the reaction. Furthermore, a continuous-flow reactor can be easily integrated with different solar collectors (including compound parabolic concentrators and luminescent solar concentrators) and constitutes the most efficient approach to solar photochemistry. After a description of the characteristics of the solar radiation relevant to chemistry, this chapter critically describes the different type of solar photoreactors and their applications in synthetic organic chemistry. Finally, an outlook on the future of solar photochemistry in flow is included.

Continuous Endoperoxidation of Conjugated Dienes and Subsequent Rearrangements Leading to C-H Oxidized Synthons

We have investigated the continuous flow photooxidation of several conjugated dienes and subsequent rearrangement using a practical and safe continuous-flow homemade engineered setup. End-to-end approaches involving endoperoxidation, Kornblum-DeLaMare rearrangement, and additional rearrangements are comprehensively detailed with optimization, scope, and scale-up to obtain useful hydroxyenones, furans, and 1,4-dicarbonyl building blocks.