A Divergent Paired Electrochemical Process for the Conversion of Furfural Using a Divided-Cell Flow Microreactor

Biomass Valorization via Paired Electrocatalysis

Electrochemical valorization of biomass represents an emerging research frontier, capitalizing on renewable feedstocks to mitigate carbon emissions. Traditional electrochemical approaches often suffer from energy inefficiencies due to the requirement of a second electrochemical conversion at the counter electrode which might generate non-value-added byproducts. This review article presents the advancement of paired electrocatalysis as an alternative strategy, wherein both half-reactions in an electrochemical cell are harnessed to concurrently produce value-added chemicals from biomass-derived feedstocks, potentially doubling the Faradaic efficiency of the whole process. The operational principles and advantages of different cell configurations, including 1-compartment undivided cells, H-type cells, and flow cells, in the context of paired electrolysis are introduced and compared, followed by the analysis of various catalytic strategies, from catalyst-free systems to sophisticated homogeneous and heterogeneous electrocatalysts, tailored for optimized performance. Key substrates, such as CO2, 5-hydroxymethylfurfural (HMF), furfural, glycerol, and lignin are highlighted to demonstrate the versatility and efficacy of paired electrocatalysis. This work aims to provide a clear understanding of why and how both cathode and anode reactions can be effectively utilized in electrocatalytic biomass valorization leading to innovative industrial scalability.

Electrochemical Hydrodimerization of Lignocellulose-Derived Carbonyls in Aqueous Electrolytes for Biobased Polymer and Long-chained Synfuel Production: A Review

The transformation from fossil resources, crude oil and natural gas to biomass-derived feedstocks is an urgent and major challenge for the chemical industry. The valorization of lignocellulose as renewable resource is a promising pathway offering access to a wide range of platform chemicals, such as vanillin, furfural and 5-HMF. The subsequent conversion of such platform chemicals is one crucial step in the value-added chain. The electrochemical hydrodimerization (EHD) is a sustainable tool for C-C coupling of these chemicals to their corresponding hydrodimers hydrovanilloin, hydrofuroin and 5,5'-bis(hydroxymethyl)hydrofuroin (BHH). This review covers the current state of art concerning the mechanism of the electrochemical reduction of biobased aldehydes and studies targeting the electrochemical production of these hydrodimers in aqueous media. Moreover, the subsequent conversion of these hydrodimers to valuable additives, polymers and long carbon chain synfuels will be summarized offering a broad scope for their application in the chemical industry.

MXene Electrocatalysts: Transformative Approaches in Hydrogen Production with Alternative Anode Reactions

Water electrolyzer is crucial for producing clean hydrogen, but the traditional approach faces challenges owing to the oxygen evolution reaction (OER) slow kinetics at the anode. Hybrid water splitting replaces the OER with the oxidation of an organic molecule to enhance hydrogen production along with value-added products. The scarcity of affordable and highly effective catalysts remains a major challenge. MXene, a 2D nanomaterial, has gained substantial attention for its enviable properties, for instance high conductivity, hydrophilicity, and substantial surface area. This review discusses experimental methods for synthesizing MXene and MXene-based nanocomposites. Furthermore, the small molecules oxidation such as benzyl alcohol, methanol, ethanol, urea, hydrazine, furfural, and formic acid as alternatives to the oxygen evolution reaction is examined. Finally, an understanding of imminent research and the development of MXene-associated materials in electrocatalytic applications are presented.

Paired Electrolysis Enabled Trifluoromethylheteroaromatization of Alkenes and Alkyne with Trifluoromethyl Thianthrenium Triflate (TT-CF3+OTf-) as a Bifunctional Reagent

We report a strategic exploitation of trifluoromethyl thianthrenium triflate (TT-CF3+OTf-) as both electromediator and CF3 radical precursors for paired electrolysis. Enabled by this strategy, the three-component trifluoromethylheteroaromatization of alkenes and alkynes was realized. The superiority of TT-CF3+OTf- to other electrophilic CF3 reagents is attributed to the cathodic generation of thianthrene (TT) as a mediator, which shifts the heterogeneous oxidation of interest to a homogeneous one.

A perspective on automated advanced continuous flow manufacturing units for the upgrading of biobased chemicals toward pharmaceuticals

Biomass is a renewable, almost infinite reservoir of a large diversity of highly functionalized chemicals. The conversion of biomass toward biobased platform molecules through biorefineries generally still lacks economic viability. Profitability could be enhanced through the development of new market opportunities for these biobased platform chemicals. The fine chemical industry, and more specifically the manufacturing of pharmaceuticals is one of the sectors bearing significant potential for these biobased building blocks to rapidly emerge and make a difference. There are, however, still many challenges to be dealt with before this market can thrive. Continuous flow technology and its integration for the upgrading of biobased platform molecules for the manufacturing of pharmaceuticals is foreseen as a game-changer. This perspective reflects on the main challenges relative to chemical, process, regulatory and supply chain-related burdens still to be addressed. The implementation of integrated continuous flow processes and their automation into modular units will help for tackling with these challenges.

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Recent Advances in C(sp3)-C(sp3) and C(sp3)-C(sp2) Bond Formation through Cathodic Reactions: Reductive and Convergent Paired Electrolyses

The formation of C(sp³)-C(sp³) and C(sp³)-C(sp²) bonds is one of the major research goals of synthetic chemists. Electrochemistry is commonly considered to be an appealing means to drive redox reactions in a safe and sustainable fashion and has been utilized for C-C bond-forming reactions. Compared to anodic oxidative methods, which have been extensively explored, cathodic processes are much less investigated, whereas it can pave the way to alternative retrosynthetic disconnections of target molecules and to the discovery of new transformations. This review provides an overview on the recent achievements in the construction of C(sp³)-C(sp³) and C(sp³)-C(sp²) bonds via cathodic reactions since 2017. It includes electrochemical reductions and convergent paired electrolyses.

Electrochemical Radiofluorination of Small Molecules: New Advances

The development of new ¹⁸ F-based radiopharmaceuticals constantly demands innovations in the search for new radiofluorination methods. [¹⁸ F]fluoride is the simplest and most convenient chemical form of the isotope for the synthesis of ¹⁸ F-based radiopharmaceuticals. The ease of production and handling, as well as the possibility of obtaining high molar activities, makes it the preferred choice for radiofluorination. However, the use of [¹⁸ F]fluoride in late-stage radiofluorination comes with challenges, especially for the radiolabeling of electron-rich molecules where S_N 2 and S_N Ar reactions are not suitable. New developments in fluorination chemistry have been extensively studied to overcome these difficulties. Selective electrochemical oxidation of precursors, using a controlled potential, is one method to create reactive intermediates and overcome the activation energy required for nucleophilic fluorination of electron-rich moieties. This method has been used for years in cold fluorination of organic molecules and more recently has been adapted as an alternative to traditional radiofluorination methods. Although relatively young, this field stands out as a promising route for the synthesis of new PET probes as well as fluorinated pharmaceuticals. This review focuses on recent advances in electrochemical radiofluorination as an alternative for the late-stage radiolabeling of organic molecules.

Organic Electrosynthesis Towards Sustainability: Fundamentals and Greener Methodologies

The adoption of new measures that preserve our environment, on which our survival depends, is a necessity. Electro-organic processes are sustainable per se, by producing the activation of a substrate by electron transfer at normal pressure and room temperature. In the recent years, a highly crescent number of works on organic electrosynthesis are available. Novel strategies at the electrode are being developed enabling the construction of a great variety of complex organic molecules. However, the possibility of being scaled-up is mandatory in terms of sustainability. Thus, some electrochemical methodologies have demonstrated to report the best results in reducing pollution and saving energy. In this personal account, these methods have been compiled, being organized as follows: • Direct discharge electrosynthesis • Paired electrochemical reactions. and • Organic transformations utilizing electrocatalysis (in absence of heavy metals). Selected protocols are herein presented and discussed with representative recent examples. Final perspectives and reflections are also considered.

Electrocatalytic hydrogenation of furfural paired with photoelectrochemical oxidation of water and furfural in batch and flow cells

The simultaneous formation of furfuryl alcohol and furoic acid was achieved from electrocatalytic hydrogenation and photoelectrochemical oxidation of furfural, respectively.

Kinetics of furfural electrochemical hydrogenation and hydrogenolysis in acidic media on copper

This article reports the competing kinetics and insights into the mechanisms of the electrochemical hydrogenation and hydrogenolysis of furfural to furfuryl alcohol and 2-methylfuran.