Highly Selective Solar-Driven Methanol from CO2 by a Photocatalyst/Biocatalyst Integrated System

Synergistic effects of covalently coupled eosin-Y with Ben-graphitic carbon nitride framework for improved photocatalytic activity in solar light-driven Biginelli product generation and NADH regeneration

Elevated global pollution level is the prime reason that contributes to the onset of various harmful health diseases. The products of Biginelli reaction are enormously used in the pharmaceutical industry as they have antiviral, antibacterial, and calcium channel modulation abilities. This work reports a novel eosin Y sensitized boron graphitic carbon nitride (EY-Ben-g-C3N4) as a photocatalyst that efficiently produced 3,4-dihydropyrimidine-2-(1H)-one by the Biginelli reaction of benzaldehyde, urea, and methyl acetoacetate. The photocatalyst EY-Ben-g-C3N4 showed a successful generation of 3,4-dihydropyrimidine-2-(1H)-one (Biginelli product) in good yield via photocatalysis which is an eco-friendly method and has facile operational process. In addition to the production of Biginelli products, the photocatalyst also showed a remarkable NADH regeneration of 81.18%. The incorporation of g-C3N4 with boron helps increase the surface area and the incorporation of eosin Y which is an inexpensive and non-toxic dye, and in Ben-g-C3N4, enhanced the light-harvesting capacity of the photocatalyst. The production of 3,4-dihydropyrimidine-2-(1H)-one and NADH by the EY-Ben-g-C3N4 photocatalyst is attributed to the requisite band gap, high molar absorbance, low rate of charge recombination, and increased capacity of the photocatalyst to harvest solar light energy.

A Coupled System of Ni3S2 and Rh Complex with Biomimetic Function for Electrocatalytic 1,4-NAD(P)H Regeneration

NAD(P)H cofactor is a critical energy and electron carrier in biocatalysis and photosynthesis, but the artificial reduction of NAD(P)+ to regenerate bioactive 1,4-NAD(P)H with both high activity and selectivity is challenging. Herein, we found that a coupled system of a Ni3S2 electrode and a Rh complex in an electrolyte (denoted as Ni3S2-Rh) can catalyze the reduction of NAD(P)+ to 1,4-NAD(P)H with superior activity and selectivity. The optimized selectivity in 1,4-NADH can be up to 99.1%, much higher than that for Ni3S2 (80%); the normalized activity of Ni3S2-Rh is about 5.8 times that of Ni3S2 and 13.2 times that of the Rh complex. The high performance of Ni3S2-Rh is attributed to the synergistic effect between metal sulfides and Rh complex. The NAD+ reduction reaction proceeds via a concerted electron-proton transfer (CEPT) mechanism in the Ni3S2-Rh system, in which Ni3S2 acts as a proton and electron-transfer mediator to accelerate the formation of Rh hydride (Rh-H), and then the Rh-H regioselectively transfers the hydride to NAD+ to form 1,4-NADH. The artificial system Ni3S2-Rh essentially mimics the functions of ferredoxin-NADP+ reductase in nature.

Visible light-driven oxidation of non-native substrate by laccase attached on Ru-based metal-organic frameworks

Light-induced electron transfer can broaden the substrate range of metalloenzyme. However, the efficiency of photo-enzyme coupling is limited by the poor combination of photosensitizer or photocatalyst with enzyme. Herein, we prepared the nano-photocatalyst MIL-125-NH2@Ru(bpy) by in site embedding ruthenium pyridine-diimine complex [Ru(bpy)3]2+ into metal organic frameworks MIL-125-NH2 and associated it with multicopper oxidase (MCO) laccase. Compared to [Ru(bpy)3]2+, the coupling efficiency of MIL-125-NH2@Ru(bpy)3 for enzymatic oxygen reduction increased by 35.7%. A series of characterizations confirmed that the amino group of laccase formed chemical bonds with the surface defects or hydrophobic groups of MIL-125-NH2@Ru(bpy)3. Consequently, the tight binding accelerated the quenching process and electron transfer between laccase and the immobilized ruthenium pyridine-diimine complex. This work would open an avenue for the synthesis of MOFs photocatalyst towards photo-enzyme coupling.

Photoenzymatic CO2 Reduction Dominated by Collaborative Matching of Linkage and Linker in Covalent Organic Frameworks

Artificial photoenzymatic systems based on covalent organic frameworks (COFs) provide an interesting platform for converting CO2 to value-added fuels. However, the dual roles of COFs as photocatalysts and enzyme hosts showcase contradictory preferences for structures, which poses a great challenge for their rational design. Herein, we report the collaborative matching of linkages and linkers in COFs on their ability to exert both photocatalytic activity and enzyme loading, which has been neglected until now. The linkage-dependent linker regulation pattern was elucidated, and the optimal match showed a record-breaking apparent quantum efficiency at 420 nm for photocatalytic cofactor regeneration of 13.95% with a high turnover frequency of 5.3 mmol g-1 h-1, outperforming other reported crystalline framework photocatalysts. Moreover, theoretical calculations and experiments revealed the mechanism underlying the effects of matching the linkage and linker on exciton dissociation and charge migration in photocatalysis. This newfound understanding enabled the construction of COFs with both high photoactivity and large pores closer in size to the formate dehydrogenase, achieving high loading capacity and a suitable confinement effect. Remarkably, the artificial photoenzymatic system constructed according to optimal linkage-linker matching exhibited highly efficient CO2 reduction, yielding formic acid with a specific activity as high as 1.46 mmol g-1 catalyst h-1 and good reusability, paving the way for sustainable CO2 conversion driven by visible light.

Aloe vera-derived graphene-coupled phenosafranin photocatalyst for generation and regeneration of ammonia and NADH by mimicking natural photosynthetic route

Aloe vera-derived graphene (ADG) coupled system photocatalyst, mimicking natural photosynthesis, is one of the most promising ways for converting solar energy into ammonia (NH3 ) and nicotinamide adenine dinucleotide (NADH) that have been widely used to make the numerous chemicals such as fertilizer and fuel. In this study, we report the synthesis of the aloe vera-derived graphene-coupled phenosafranin (ADGCP) acting as a highly efficient photocatalyst for the generation of NH3 and regeneration of NADH from nitrogen (N2 ) and oxidized form of nicotinamide adenine dinucleotide (NAD+ ). The results show a benchmark instance for mimicking natural photosynthesis activity as well as the practical applications for the solar-driven selective formation of NH3 and the regeneration of NADH by using the newly designed photocatalyst.

Revolutionizing carbon chemistry: Solar-powered C(sp3 )-N bond activation and CO2 transformation via newly designed SBE-Y cutting-edge dynamic photocatalyst

A solvent-free sulfur-bridge-eosin-Y (SBE-Y) polymeric framework photocatalyst was prepared for the first time through an in situ thermal polymerization route using elemental sulfur (S8 ) as a bridge. The addition of a sulfur bridge to the polymeric framework structure resulted in an allowance of the harvesting range of eosin-Y (E-Y) for solar light. This shows that a wider range of solar light can be used by the bridge material's photocatalytic reactions. In this context, supercharged solar spectrum: enhancing light absorption and hole oxidation with sulfur bridges. This suggests that the excited electrons and holes through solar light can contribute to oxidation-reduction reactions more potently. As a result, the photocatalyst-enzyme attached artificial photosynthesis system developed using SBE-Y as a photocatalyst performs exceptionally well, resulting in high 1,4-NADH regeneration (86.81%), followed by its utilization in the exclusive production of formic acid (210.01 μmol) from CO2 and synthesis of fine chemicals with 99.9% conversion yields. The creation of more effective photocatalytic materials for environmental clean-up and other applications that depend on the solar light-driven absorption spectrum of inorganic and organic molecules could be one of the practical ramifications of this research.

Light-Driven CO2 Reduction with a Surface-Displayed Enzyme Cascade-C3N4 Hybrid

Efficient and cost-effective conversion of CO2 to biomass holds the potential to address the climate crisis. Light-driven CO2 conversion can be realized by combining inorganic semiconductors with enzymes or cells. However, designing enzyme cascades for converting CO2 to multicarbon compounds is challenging, and inorganic semiconductors often possess cytotoxicity. Therefore, there is a critical need for a straightforward semiconductor biohybrid system for CO2 conversion. Here, we used a visible-light-responsive and biocompatible C3N4 porous nanosheet, decorated with formate dehydrogenase, formaldehyde dehydrogenase, and alcohol dehydrogenase to establish an enzyme-photocoupled catalytic system, which showed a remarkable CO2-to-methanol conversion efficiency with an apparent quantum efficiency of 2.48% in the absence of externally added electron mediator. To further enable the in situ transformation of methanol into biomass, the enzymes were displayed on the surface of Komagataella phaffii, which was further coupled with C3N4 to create an organic semiconductor-enzyme-cell hybrid system. Methanol was produced through enzyme-photocoupled CO2 reduction, achieving a rate of 4.07 mg/(L·h), comparable with reported rates from photocatalytic systems employing mediators or photoelectrochemical cells. The produced methanol can subsequently be transported into the cell and converted into biomass. This work presents a sustainable, environmentally friendly, and cost-effective enzyme-photocoupled biocatalytic system for efficient solar-driven conversion of CO2 within a microbial cell.

Highly Efficient Self-Assembled Activated Carbon Cloth-Templated Photocatalyst for NADH Regeneration and Photocatalytic Reduction of 4-Nitro Benzyl Alcohol

This manuscript emphasizes how structural assembling can facilitate the generation of solar chemicals and the synthesis of fine chemicals under solar light, which is a challenging task via a photocatalytic pathway. Solar energy utilization for pollution prevention through the reduction of organic chemicals is one of the most challenging tasks. In this field, a metal-based photocatalyst is an optional technique but has some drawbacks, such as low efficiency, a toxic nature, poor yield of photocatalytic products, and it is expensive. A metal-free activated carbon cloth (ACC)–templated photocatalyst is an alternative path to minimize these drawbacks. Herein, we design the synthesis and development of a metal-free self-assembled eriochrome cyanine R (EC-R) based ACC photocatalyst (EC-R@ACC), which has a higher molar extinction coefficient and an appropriate optical band gap in the visible region. The EC-R@ACC photocatalyst functions in a highly effective manner for the photocatalytic reduction of 4-nitro benzyl alcohol (4-NBA) into 4-amino benzyl alcohol (4-ABA) with a yield of 96% in 12 h. The synthesized EC-R@ACC photocatalyst also regenerates reduced forms of nicotinamide adenine dinucleotide (NADH) cofactor with a yield of 76.9% in 2 h. The calculated turnover number (TON) of the EC-R@ACC photocatalyst for the reduction of 4-nitrobenzyl alcohol is 1.769 × 1019 molecules. The present research sets a new benchmark example in the area of organic transformation and artificial photocatalysis.

Development of an Integrated System for Highly Selective Photoenzymatic Synthesis of Formic Acid from CO2

Herein, a Zr-based dual-ligand MOFs with pre-installed Rh complex was employed for NADH regeneration in situ and also used for immobilization of formic acid dehydrogenase (FDH) in order to realize a highly efficient CO₂ fixation system. Then, based on the detailed investigations into the photochemical and electrochemical properties, it is demonstrated that the introduction of the photosensitive meso-tetra(4-carboxyphenyl) porphin (TCPP) ligands increased the catalytic active sites and improved photoelectric properties. Furthermore, the electron mediator Rh complex, anchored on the zirconium-based dual-ligand MOFs, enhanced the efficiency of electron transfer efficiency and facilitated the separation of photogenerated electrons and holes. Compared with UiO-66-NH₂ , Rh-H₂ TCPP-UiO-66-NH₂ exhibits an optimized valence band structure and significantly improved photocatalytic activity for NAD⁺ reduction, resulting the synthesis of formic acid from CO₂ increased from 150 μg mL^-1 (UiO-66-NH₂ ) to 254 μg mL^-1 (Rh-H₂ TCPP-UiO-66-NH₂ ). Moreover, the assembled photocatalyst-enzyme coupled system also allows facile recycling of expensive electron mediator, enzyme, and photocatalyst.

Highly Selective Nitrogen-Doped Graphene Quantum Dots/Eriochrome Cyanine Composite Photocatalyst for NADH Regeneration and Coupling of Benzylamine in Aerobic Condition under Solar Light

Photocatalysis is an ecofriendly and sustainable pathway for utilizing solar energy to convert organic molecules. In this context, using solar light responsive graphene-based materials for C–N bond activation and coenzyme regeneration (nicotinamide adenine dinucleotide hydrogen; NADH) is one of the utmost important and challenging tasks in this century. Herein, we report the synthesis of nitrogen-doped graphene quantum dots (NGQDs)-eriochrome cyanine (EC) solar light active highly efficient “NGQDs@EC” composite photocatalyst for the conversion of 4-chloro benzylamine into 4-chloro benzylamine, accompanied by the regeneration of NADH from NAD+, respectively. The NGQDs@EC composite photocatalyst system is utilized in a highly efficient and stereospecific solar light responsive manner, leading to the conversion of imine (98.5%) and NADH regeneration (55%) in comparison to NGQDs. The present research work highlights the improvements in the use of NGQDs@EC composite photocatalyst for stereospecific NADH regeneration and conversion of imine under solar light.

Electrocatalytic NAD+ reduction via hydrogen atom-coupled electron transfer

Nicotinamide adenine dinucleotide cofactor (NAD(P)H) is regarded as an important energy carrier and charge transfer mediator. Enzyme-catalyzed NADPH production in natural photosynthesis proceeds via a hydride transfer mechanism. Selective and effective regeneration of NAD(P)H from its oxidized form by artificial catalysts remains challenging due to the formation of byproducts. Herein, electrocatalytic NADH regeneration and the reaction mechanism on metal and carbon electrodes are studied. We find that the selectivity of bioactive 1,4-NADH is relatively high on Cu, Fe, and Co electrodes without forming commonly reported NAD2 byproducts. In contrast, more NAD2 side product is formed with the carbon electrode. ADP-ribose is confirmed to be a side product caused by the fragmentation reaction of NAD+. Based on H/D isotope effects and electron paramagnetic resonance analysis, it is proposed that the formation of NADH on these metal electrodes proceeds via a hydrogen atom-coupled electron transfer (HadCET) mechanism, in contrast to the direct electron-transfer and NAD˙ radical pathway on carbon electrodes, which leads to more by-product, NAD2. This work sheds light on the mechanism of electrocatalytic NADH regeneration, which is different from biocatalysis.

Advances in Biomimetic Photoelectrocatalytic Reduction of Carbon Dioxide

Emerging photoelectrocatalysis (PEC) systems synergize the advantages of electrocatalysis (EC) and photocatalysis (PC) and are considered a green and efficient approach to CO₂ conversion. However, improving the selectivity and conversion rate remains a major challenge. Strategies mimicking natural photosynthesis provide a prospective way to convert CO₂ with high efficiency. Herein, several typical strategies are described for constructing biomimetic photoelectric functional interfaces; such interfaces include metal cocatalysts/semiconductors, small molecules/semiconductors, molecular catalysts/semiconductors, MOFs/semiconductors, and microorganisms/semiconductors. The biomimetic PEC interface must have enhanced CO₂ adsorption capacity, preferentially activate CO₂ , and have an efficient conversion ability; with these properties, it can activate CO bonds effectively and promote electron transfer and CC coupling to convert CO₂ to single-carbon or multicarbon products. Interfacial electron transfer and proton coupling on the biomimetic PEC interface are also discussed to clarify the mechanism of CO₂ reduction. Finally, the existing challenges and perspectives for biomimetic photoelectrocatalytic CO₂ reduction are presented.

Improving the Enzymatic Cascade of Reactions for the Reduction of CO2 to CH3OH in Water: From Enzymes Immobilization Strategies to Cofactor Regeneration and Cofactor Suppression

The need to decrease the concentration of CO2 in the atmosphere has led to the search for strategies to reuse such molecule as a building block for chemicals and materials or a source of carbon for fuels. The enzymatic cascade of reactions that produce the reduction of CO2 to methanol seems to be a very attractive way of reusing CO2; however, it is still far away from a potential industrial application. In this review, a summary was made of all the advances that have been made in research on such a process, particularly on two salient points: enzyme immobilization and cofactor regeneration. A brief overview of the process is initially given, with a focus on the enzymes and the cofactor, followed by a discussion of all the advances that have been made in research, on the two salient points reported above. In particular, the enzymatic regeneration of NADH is compared to the chemical, electrochemical, and photochemical conversion of NAD+ into NADH. The enzymatic regeneration, while being the most used, has several drawbacks in the cost and life of enzymes that suggest attempting alternative solutions. The reduction in the amount of NADH used (by converting CO2 electrochemically into formate) or even the substitution of NADH with less expensive mimetic molecules is discussed in the text. Such an approach is part of the attempt made to take stock of the situation and identify the points on which work still needs to be conducted to reach an exploitation level of the entire process.

Strategies for overcoming the limitations of enzymatic carbon dioxide reduction

The overexploitation of fossil fuels has led to a significant increase in atmospheric carbon dioxide (CO₂) concentrations, thereby causing problems, such as the greenhouse effect. Rapid global climate change has caused researchers to focus on utilizing CO₂ in a green and efficient manner. One of the ways to achieve this is by converting CO₂ into valuable chemicals via chemical, photochemical, electrochemical, or enzymatic methods. Among these, the enzymatic method is advantageous because of its high specificity and selectivity as well as the mild reaction conditions required. The reduction of CO₂ to formate, formaldehyde, and methanol using formate dehydrogenase (FDH), formaldehyde dehydrogenase (F_aldDH), and alcohol dehydrogenase (ADH) are attractive routes, respectively. In this review, strategies for overcoming the common limitations of enzymatic CO₂ reduction are discussed. First, we present a brief background on the importance of minimizing of CO₂ emissions and introduce the three bottlenecks limiting enzymatic CO₂ reduction. Thereafter, we explore the different strategies for enzyme immobilization on various support materials. To solve the problem of cofactor consumption, different state-of-the-art cofactor regeneration strategies as well as research on the development of cofactor substitutes and cofactor-free systems are extensively discussed. Moreover, aiming at improving CO₂ solubility, biological, physical, and engineering measures are reviewed. Finally, conclusions and future perspectives are presented.

Natural Deep Eutectic Solvents Enhanced Electro-Enzymatic Conversion of CO2 to Methanol

Electro-enzymatic conversion of CO₂ offers a promising solution for CO₂ utilization, while the conversion rate and efficiency were disappointing. To address the challenge, four kinds of natural deep eutectic solvents (NADES) with desirable biocompatibility were developed for the first time and used as the co-electrolyte in the electro-enzymatic conversion of CO₂. As a result, the SerGly-based solution presents high CO₂ solubility and high electrocatalytic activity, compared to the conventional buffer. By applying SerGly in the electro-enzymatic conversion of CO₂, the yield of the product (methanol) is two times higher than that in the Tris-HCl buffer (0.22 mM) and 16 times higher than the control reaction.

Engineering Olefin-Linked Covalent Organic Frameworks for Photoenzymatic Reduction of CO2

It is of profound significance concerning the global energy and environmental crisis to develop new techniques that can reduce and convert CO₂ . To address this challenge, we built a new type of artificial photoenzymatic system for CO₂ reduction, using a rationally designed mesoporous olefin-linked covalent organic framework (COF) as the porous solid carrier for co-immobilizing formate dehydrogenase (FDH) and Rh-based electron mediator. By adjusting the incorporating content of the Rh electronic mediator, which facilitates the regeneration of nicotinamide cofactor (NADH) from NAD⁺ , the apparent quantum yield can reach as high as 9.17±0.44 %, surpassing all reported NADH-regenerated photocatalysts constructed by crystalline framework materials. Finally, the assembled photocatalyst-enzyme coupled system can selectively convert CO₂ to formic acid with high efficiency and good reusability. This work demonstrates the first example using COFs to immobilize enzymes for artificial photosynthesis systems that utilize solar energy to produce value-added chemicals.

Greener One Step Synthesis of Novel In-situ Selenium-Doped Frameworks Photocatalyst by Melem and Perylene Dianhydride for Enhanced Solar Fuel Production from CO2

To minimize the ever-increasing global warming and environmental problems, the conversion of atmospheric CO₂ into value-added solar chemicals/fuels is one of the most challenging tasks. As a means to accomplish this, herein we have synthesized first time novel in situ selenium doped polyimide frameworks (Se-PIFs) photocatalyst via thermal co-polymerization approach between melem (M) and perylene 3, 4, 9, 10- tetracarboxylic dianhydride (PTDA) along with selenium (Se) as a dopant. The Se-PIFs photocatalyst shows outstanding photocatalytic stability and activity for high solar fuel production (HCOOH ~ formic acid) from CO₂ . The solar light active Se-PIFs photocatalyst was demonstrating the ~ 10 fold higher photo-conversion of CO₂ to formic acid with yields of 250. 6 μmol. The current work is providing a facile and scalable avenue as well as sheds light on creating a new route for in-situ judicious design highly efficient Se-PIFs photocatalyst. The outcome are a benchmark instance for the use of selenium doped polyimide frameworks as a highly practical and efficient solar light active photocatalyst for carrying out the selective production of formic acid from environmental CO₂ .

Chiral NADH Model: Design, Synthesis, Asymmetric Reduction Reaction and Fluorescence Characteristics

Abstract:

A new type of NADH model compound, which has six asymmetric carbon centers, has been synthesized by an efficient and convenient method. We preliminarily attempted that NADH models combined with enzyme were used in the asymmetric reduction. It is the first time that dehydrogenase with NADH models instead of inorganic catalysts such as MgCl2 were used in the asymmetric reduction. Furthermore, the experimental results showed that the new NADH model has the strongest fluorescence emission properties compared with previous reported models.

Developing and Regenerating Cofactors for Sustainable Enzymatic CO2 Conversion

Enzymatic CO2 conversion offers a promising strategy for alleviating global warming and promoting renewable energy exploitation, while the high cost of cofactors is a bottleneck for large-scale applications. To address the challenge, cofactor regeneration is usually coupled with the enzymatic reaction. Meanwhile, artificial cofactors have been developed to further improve conversion efficiency and decrease cost. In this review, the methods, such as enzymatic, chemical, electrochemical, and photochemical catalysis, developed for cofactor regeneration, together with those developed artificial cofactors, were summarized and compared to offer a solution for large-scale enzymatic CO2 conversion in a sustainable way.

Synthesis of highly efficient selenium oxide hybridized g-C3N4 photocatalyst for NADH/NADPH regeneration to facilitate solar-to-chemical reaction

An inexpensive graphitic carbon nitrite (g-C3N4) photocatalyst was hybridized with selenium oxide (SeO2) photocatalyst by a monolayer-dispersed technique. After hybridization of g-C3N4 with SeO2, the NADH/NADPH regeneration efficiency of SeO2 photocatalyst was enhanced under solar light illumination was observed. The photocatalytic activity of SeO2/g-C3N4 photocatalyst under solar light illumination was enhanced by 3-fold higher than g-C3N4 photocatalyst, the solar light photocatalytic activity was produced and the photo-decomposition of SeO2 photocatalyst was completely stifled after hybridized SeO2 photocatalyst by g-C3N4 photocatalyst. The improvement in performance and photo-decomposition inhibition under solar light illumination was persuaded by efficiency separation of photo-persuaded holes from SeO2 to the valence bond (V.B.)/highest occupied molecular orbital (HOMO) of g-C3N4 under solar light illumination, the electron jumped from the V.B. to the conduction band (C.B.)/lowest unoccupied molecular orbital (LUMO) of g-C3N4 could directly insert into the C.B. of SeO2 photocatalyst, synthesized SeO2/g-C3N4 photocatalyst is highly active for NADH/NADPH regeneration under solar light.

No competitive inhibition of bicarbonate or carbonate for formate dehydrogenase from Candida boidinii -catalyzed CO2 reduction

Formate dehydrogenase from Candida boidinii (CbFDH) reversibly catalyzes the formate to CO2 with the redox coupling NAD+/NADH. While many studies on CbFDH-catalyzed formate oxidation in the presence of NAD+ are...

CO2 to Methanol: A Highly Efficient Enzyme Cascade

Carbon dioxide (CO₂) has been increasingly regarded not only as a greenhouse gas but also as a valuable feedstock for carbon-based chemicals. In particular, biological approaches have drawn attention as models for the production of value-added products, as CO₂ conversion serves many natural processes. Enzymatic CO₂ reduction in vitro is a very promising route to produce fossil free and bio-based fuel alternatives, such as methanol. In this chapter, the advances in constructing competitive multi-enzymatic systems for the reduction of CO₂ to methanol are discussed. Different integrated methods are presented, aiming to address technological challenges, such as the cost effectiveness, need for material regeneration and reuse and improving product yields of the process.

Carbonic anhydrase/formate dehydrogenase bienzymatic system for CO2 capture, utilization and storage

In order to establish carbon capture, utilization, and storage (CCUS) technology, a system consisting of two different biocatalysts (formate dehydrogenase from Candida boidinii; CbFDH and carbonic anhydrase from bovine erythrocytes; CA) is developed.

The Efficient Synthesis of 2-(3-Carbamoylpyridine-2-yl) Nicotinamide Pyridine Salts

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The synthesis of axially chiral compounds has attracted a great deal of attention in recent years. Herein, an efficient and economical synthetic route has been developed for 2-(3- carbamoylpyridin-2-yl) nicotinamide pyridine salts, axially chiral compounds. The starting material 1,10-phenanthroline is readily available. In this study, 2-(3-carbamoylpyridin-2-yl) nicotinamide pyridine salts are obtained in moderate to good yields. This protocol includes simple operations and has easy scalability. In addition, the axial chirality of the products is also preliminary studied.

Solar-driven conversion of carbon dioxide over nanostructured metal-based catalysts in alternative approaches: Fundamental mechanisms and recent progress

Solar-driven carbon dioxide (CO₂) conversion has gained tremendous attention as a prominent strategy to simultaneously reduce the atmospheric CO₂ concentration and convert solar energy into solar fuels in the form of chemical bonds. Numerous efforts have been devoted to diverse photo-driven processes for CO₂ conversion, which utilized a multidisciplinary strategy. Among them, the architecture of nanostructured metal-based catalysts is emerging as an eminent solution for the design of catalysts of this field. In this work, we first provide fundamental mechanisms of photochemical, photoelectrochemical, photothermal, and photobio(electro)chemical CO₂ reduction processes to achieve an in-deep understanding of vital aspects. Importantly, the recent progress in the catalyst design for each reaction system is discussed and highlighted. Based on these analyses, an overview of photo-driven CO₂ reduction on metal-based catalysts for solar fuel production is also spotlighted. Finally, we analyze challenges and prospects for the strategic direction of developments in the field.

Stereodivergent synthesis of β-iodoenol carbamates with CO2 via photocatalysis

Photocatalytic conversion of carbon dioxide (CO2) into value-added chemicals is of great significance from the viewpoint of green chemistry and sustainable development. Here, we report a stereodivergent synthesis of β-iodoenol carbamates through a photocatalytic three-component coupling of ethynylbenziodoxolones, CO2 and amines. By choosing appropriate photocatalysts, both Z- and E-isomers of β-iodoenol carbamates, which are difficult to prepare using existing methods, can be obtained stereoselectively. This transformation featured mild conditions, excellent functional group compatibility and broad substrate scope. The potential synthetic utility of this protocol was demonstrated by late-stage modification of bioactive molecules and pharmaceuticals as well as by elaborating the products to access a wide range of valuable compounds. More importantly, this strategy could provide a general and practical method for stereodivergent construction of trisubstituted alkenes such as triarylalkenes, which represents a fascinating challenge in the field of organic chemistry research. A series of mechanism investigations revealed that the transformation might proceed through a charge-transfer complex which might be formed through a halogen bond.

Highly Efficient Flower-Like Graphene Quantum Dots-Based Fuschin Photocatalyst for Selective NAD(P)H Cofactor Regeneration Under Solar Light Irradiation

To meet the energy demands artificial photosynthesis is playing the most promising role these days. Using sunlight directly in a manner that can provide useful chemicals is a sustainable means of generating energy. Studies are going on in this context to make better and effective photocatalyst. In this paper, we study the synthesis of flower-like graphene quantum dots-based fuschin (GQDF) photocatalyst from lemon_, which is created by a green and sustainable process that is effective and environment friendly. The UV-visible spectra of prepared GQDF showed a high molar extinction coefficient. A flower-like GQDF photocatalyst has better catalytic efficiency for the selective creation and regeneration of the NAD(P)H cofactor. A newly designed flower-like GQDF photocatalyst is used as one of its most effective photocatalysts as they have several additional applications in the removal of CO₂ and aqueous contaminants like heavy metals.

Enzymes, In Vivo Biocatalysis, and Metabolic Engineering for Enabling a Circular Economy and Sustainability

Since the industrial revolution, the rapid growth and development of global industries have depended largely upon the utilization of coal-derived chemicals, and more recently, the utilization of petroleum-based chemicals. These developments have followed a linear economy model (produce, consume, and dispose). As the world is facing a serious threat from the climate change crisis, a more sustainable solution for manufacturing, i.e., circular economy in which waste from the same or different industries can be used as feedstocks or resources for production offers an attractive industrial/business model. In nature, biological systems, i.e., microorganisms routinely use their enzymes and metabolic pathways to convert organic and inorganic wastes to synthesize biochemicals and energy required for their growth. Therefore, an understanding of how selected enzymes convert biobased feedstocks into special (bio)chemicals serves as an important basis from which to build on for applications in biocatalysis, metabolic engineering, and synthetic biology to enable biobased processes that are greener and cleaner for the environment. This review article highlights the current state of knowledge regarding the enzymatic reactions used in converting biobased wastes (lignocellulosic biomass, sugar, phenolic acid, triglyceride, fatty acid, and glycerol) and greenhouse gases (CO₂ and CH₄) into value-added products and discusses the current progress made in their metabolic engineering. The commercial aspects and life cycle assessment of products from enzymatic and metabolic engineering are also discussed. Continued development in the field of metabolic engineering would offer diversified solutions which are sustainable and renewable for manufacturing valuable chemicals.

General framework for enzyme-photo-coupled catalytic system toward carbon dioxide conversion

High emission of carbon dioxide (CO₂) has aroused global concern due to the 'greenhouse effect'. The conversion of CO₂ to valuable chemicals/materials is an indispensable route toward 'carbon neutrality'. Enzyme-photo-coupled catalytic systems (EPCCSs), integrating synthetic library of semiconductor photocatalyst and natural database of enzyme, have emerged as a green and powerful platform toward CO₂ conversion. Herein, we discuss the recent progress in design and application of EPCCSs for CO₂ conversion from the perspective of pathway engineering, reaction engineering and system engineering. We firstly summarize the explored pathways of EPCCSs for converting CO₂ to C₁ and C₂₊ products. Secondly, we discuss the matching of kinetics between photocatalytic and enzymatic reactions in EPCCSs. Thirdly, we unveil the complex interplay between photocatalytic and enzymatic modules, and further demonstrate the strategy of compartmentalization to eliminate the negative interactions. Lastly, we conclude with the perspective on the opportunities and challenges of EPCCSs for CO₂ conversion.

Photocatalyst-enzyme hybrid systems for light-driven biotransformation

Enzymes catalyse target reactions under mild conditions with high efficiency, as well as excellent regional-, stereo-, and enantiomeric selectivity. Photocatalysis utilises sustainable and environment-friendly light power to realise efficient chemical conversion. By combining the interdisciplinary advantages of photo- and enzymatic catalysis, the photocatalyst-enzyme hybrid systems have proceeded various light-driven biotransformation with high efficiency under environmentally benign conditions, thus, attracting unparalleled focus during the last decades. It has also been regarded as a promising pathway towards green chemistry utilising ubiquitous solar energy. This systematic review gives insight into this research field by classifying the existing photocatalyst-enzyme hybrid systems into three sections based on different hybridizing modes between photo- and enzymatic catalysis. Furthermore, existing challenges and proposed strategies are discussed within this context. The first system summarised is the cofactor-mediated hybrid system, in which natural/artificial cofactors act as reducing equivalents that connect photocatalysts with enzymes for light-driven enzymatic biotransformation. Second, the direct contact-based photocatalyst-enzyme hybrid systems are described, including two different kinds of electron exchange sites on the enzyme molecules. Third, some cases where photocatalysts and enzymes are integrated into a reaction cascade with specific intermediates will be discussed in the following chapter. Finally, we provide perspective concerning the future of this field.

Highly Efficient S-g-CN/Mo-368 Catalyst for Synergistically NADH Regeneration Under Solar Light

Sulfur-doped graphitic carbon nitride (S-g-CN) has gained significant attention in recent years. Sulfur-doped graphitic carbon nitride (S-g-CN) is a promising metal-free photocatalyst because of its band orientation, natural abundance and groundwork. Improved photocatalytic activity of S-g-CN material for solar chemical production persists a hot yet challenging problem. Herein, we provide an adaptable method for the synthesis of S-g-CN nanocomposite decorated with the moiety of giant polyoxometalate (S-g-CN/Mo-368) that subsequently showed highly efficient photocatalytic activity. The as-synthesized S-g-CN/Mo-368 as a recyclable artificial photocatalyst revealed excellent activity for solar chemical production, that is nicotinamide adenine dinucleotide (NADH) regeneration under visible light. The immobilized Mo-368 on the S-g-CN surface increased the visible light adsorption capacity of the S-g-CN/Mo-368 photocatalyst. The visible light absorption activity, morphology, element compositions, particle size and zeta potential of S-g-CN powder and S-g-CN/Mo-368 were thoroughly investigated. From the application point of view, S-g-CN/Mo-368 was applied to determine the solar chemical production (i.e. NADH regeneration) under visible light with a higher yield% of about ~ 94.85%.

Integrated catalytic insights into methanol production: Sustainable framework for CO2 conversion

A continuous increase in the amount of greenhouse gases (GHGs) is causing serious threats to the environment and life on the earth, and CO₂ is one of the major candidates. Reducing the excess CO₂ by converting into industrial products could be beneficial for the environment and also boost up industrial growth. In particular, the conversion of CO₂ into methanol is very beneficial as it is cheaper to produce from biomass, less inflammable, and advantageous to many industries. Application of various plants, algae, and microbial enzymes to recycle the CO₂ and using these enzymes separately along with CO₂-phillic materials and chemicals can be a sustainable solution to reduce the global carbon footprint. Materials such as MOFs, porphyrins, and nanomaterials are also used widely for CO₂ absorption and conversion into methanol. Thus, a combination of enzymes and materials which convert the CO₂ into methanol could energize the CO₂ utilization. The CO₂ to methanol conversion utilizes carbon better than the conventional syngas and the reaction yields fewer by-products. The methanol produced can further be utilized as a clean-burning fuel, in pharmaceuticals, automobiles and as a general solvent in various industries etc. This makes methanol an ideal fuel in comparison to the conventional petroleum-based ones and it is advantageous for a safer and cleaner environment. In this review article, various aspects of the circular economy with the present scenario of environmental crisis will also be considered for large-scale sustainable biorefinery of methanol production from atmospheric CO₂.

Enzymes for Efficient CO2 Conversion

The accumulation of carbon dioxide in the atmosphere as a result of human activities has caused a number of adverse circumstances in the world. For this reason, the proposed solutions lie within the aim of reducing carbon dioxide emissions have been quite valuable. However, as the human activity continues to increase on this planet, the possibility of reducing carbon dioxide emissions decreases with the use of conventional methods. The emergence of compounds than can be used in different fields by converting the released carbon dioxide into different chemicals will construct a fundamental solution to the problem. Although electro-catalysis or photolithography methods have emerged for this purpose, they have not been able to achieve successful results. Alternatively, another proposed solution are enzyme based systems. Among the enzyme-based systems, pyruvate decarboxylase, carbonic anhydrase and dehydrogenases have been the most studied enzymes. Pyruvate dehydrogenase and carbonic anhydrase have either been an expensive method or were incapable of producing the desired result due to the reaction cascade they catalyze. However, the studies reporting the production of industrial chemicals from carbon dioxide using dehydrogenases and in particular, the formate dehydrogenase enzyme, have been remarkable. Moreover, reported studies have shown the existence of more active and stable enzymes, especially the dehydrogenase family that can be identified from the biome. In addition to this, their redesign through protein engineering can have an immense contribution to the increased use of enzyme-based methods in CO₂ reduction, resulting in an enormous expansion of the industrial capacity.

One-Pot Highly Efficient Synthesis of N-Enrich Graphene Quantum Dots as a Photocatalytic Platform for NAD+/NADP+ Reduction

An efficient photocatalytic regeneration of nicotinamide adenine dinucleotide (NADH) and nicotinamide adenine dinucleotide phosphate (NADPH) has been carried out by two-electron reduction and protonation of NAD⁺ /NADP⁺ , induced by photons in the visible light region. This functional artificial photosynthetic counterpart of the complete energy-trapping occurring in natural photosystem I (PS I) is achieved with nitrogen-enrich graphene quantum dot (N-EGQD) as the light-harvesting photocatalyst. In buffer aqueous solution, this compound photo catalytically recycles a rhodium hydride complex of the type [Cp*Rh(bpy)H]⁺ (Cp* = pentamethylcyclopentadienyl, bpy = 2,2'-bipyridine) which can mediate hydride transfer processes leading to nucleotide co-factor reduction. Very promising yields of 73.31%/78.45% of NADH/NADPH with the excellent thermal stability of N-EGQD photocatalyst is observed. Thus, in this work, an efficient light-harvesting photocatalyst is synthesized for the regeneration of nicotinamide cofactor that has pharmaceuticals application.

Biocatalytic Reduction Reactions from a Chemist's Perspective

Reductions play a key role in organic synthesis, producing chiral products with new functionalities. Enzymes can catalyse such reactions with exquisite stereo-, regio- and chemoselectivity, leading the way to alternative shorter classical synthetic routes towards not only high-added-value compounds but also bulk chemicals. In this review we describe the synthetic state-of-the-art and potential of enzymes that catalyse reductions, ranging from carbonyl, enone and aromatic reductions to reductive aminations.

A Tandem Solar Biofuel Cell: Harnessing Energy from Light and Biofuels

We report on a photobioelectrochemical fuel cell consisting of a glucose‐oxidase‐modified BiFeO₃ photobiocathode and a quantum‐dot‐sensitized inverse opal TiO₂ photobioanode linked to FAD glucose dehydrogenase via a redox polymer. Both photobioelectrodes are driven by enzymatic glucose conversion. Whereas the photobioanode can collect electrons from sugar oxidation at rather low potential, the photobiocathode shows reduction currents at rather high potential. The electrodes can be arranged in a sandwich‐like manner due to the semi‐transparent nature of BiFeO₃, which also guarantees a simultaneous excitation of the photobioanode when illuminated via the cathode side. This tandem cell can generate electricity under illumination and in the presence of glucose and provides an exceptionally high OCV of about 1 V. The developed semi‐artificial system has significant implications for the integration of biocatalysts in photoactive entities for bioenergetic purposes, and it opens up a new path toward generation of electricity from sunlight and (bio)fuels.

A direct Z-scheme mechanism for selective hydrogenation of aromatic nitro compounds over a hybrid photocatalyst composed of ZnIn2S4 and WO3 nanorods

A direct Z-scheme mechanism photocatalyst constructed from ZnIn₂S₄ and WO₃ is a versatile photoredox platform for selective hydrogenation and environmental remediation.