Green Chemistry最新文献

Chiral thiourea, with a double hydrogen-bonding motif, has emerged as an attractive structural template for asymmetric catalysis. Catalytic synthesis of enantioenriched NH-free thiourea via functionalization of easily accessible racemic thiourea is highly desirable, albeit a formidable challenge. We herein describe NHC-catalyzed desymmetrizative amidation of axially biaryl dialdehydes, providing structurally diverse axially chiral thiourea. Sequential kinetic resolution improves the enantioenrichment of the desymmetrization product, dramatically expanding the range of applicable substrates. This strategy features a broad substrate scope and extremely excellent enantioselectivity. NHC-catalyzed desymmetrizative amidation of axially prochiral biaryl dialdehydes provides modular platforms for synthesizing challenging axially chiral thiourea and derivatives.

Due to the increasing demand for fossil fuel resources in modern society, attention is turning towards alternative sources. This paper firstly introduces the importance of the oxidation reaction of 5-hydroxymethylfurfural (HMF) and its widespread application in the field of biomass conversion. However, precise control over the selective oxidation of biomass-derived platform chemicals remains challenging, necessitating in-depth investigation into the mechanism of this oxidation process. Subsequently, the mechanism of the HMF oxidation reaction is discussed in detail, including the design and performance optimization of both traditional and novel catalysts, aiming to provide theoretical guidance and technical support for efficient and selective HMF oxidation. In the field of photocatalysis, strategies such as the introduction of photoresponsive catalysts, surface modification, and synergistic catalysis have been employed to enhance reaction rates and selectivity. In electrocatalysis, efficient conversion of HMF has been achieved through the modulation of catalyst structure and active sites. Meanwhile, photoelectrocatalysis hybrid systems, as emerging technologies integrating the advantages of both photocatalysis and electrocatalysis, demonstrate promising application prospects, with an overview of their research in HMF oxidation provided herein. Furthermore, the paper discusses the challenges faced by current selective HMF oxidation, including catalyst stability, selectivity, and product distribution, and proposes future research directions and prospects, including the design of multifunctional catalysts, optimization of reaction conditions, and in-depth exploration of catalytic mechanisms, to provide important references for achieving efficient biomass conversion. In summary, this paper systematically summarizes the latest research progress in selective photocatalysis, electrocatalysis, and photoelectrocatalysis for HMF oxidation, and provides prospects for future development, aiming to offer references and insights for relevant research fields.

This is a review on the feasibility of monolithic porous supports in biocatalysis carried out in a continuous flow system. It discusses factors affecting the efficiency and stability of enzyme immobilisation, kinetic parameters of enzyme processes carried out inside a monolith, biocatalysis in single and two-phase systems, and cascade reactions including cofactor regeneration. It also covers materials engineering (monolith types) and issues related to the flow of reactants through the monolith (chemical engineering). Emphasis is placed on the fact that the application of (bio)catalysis improves selectivity and atom economy, thus lowering the E factor. However, biocatalysts need to be employed in a reactor, which can aid further improvement towards green chemistry goals. The application of enzymes in flow chemistry has been shown to lead to higher space time yields (STYs) compared to batch reactions. In particular, with monolithic reactors a drastic decrease in volume and thus solvent can be achieved. By immobilising very high densities of enzymes directly on the monolith, reaction times dwindle, improving STYs. The small reaction volumes enable excellent heat transfer, helping to save energy. The underlying principles of monolithic flow reactors and their application in mono- and bi-phasic biocatalytic systems will be examined.

Expression of concern for ‘Preparation of polydopamine sulfamic acid-functionalized magnetic Fe₃O₄ nanoparticles with a core/shell nanostructure as heterogeneous and recyclable nanocatalysts for the acetylation of alcohols, phenols, amines and thiols under solvent-free conditions’ by Hojat Veisi et al., Green Chem., 2016, 18, 6337–6348, https://doi.org/10.1039/C6GC01975G.

The contemporary world faces issues related to energy, the environment, and food security. The use of carbon capture, storage, and utilization technologies can help reduce CO₂ emissions from fossil fuels, which will result in major advancements toward dual carbon targets. In addition to promoting environmentally friendly manufacturing, chemical industries may replace fossil fuel-based raw materials with renewable biomass for the synthesis of organic acids and syngas. Although several studies are being conducted on co-valorization of CO₂ and biomass feedstocks to produce organic acids and fine chemicals using biotechnology, thermocatalysis, electrocatalysis, and photocatalysis, there are still various obstacles in scaling up clean production, including (i) addressing environmental concerns, (ii) the intricate structure and chemical composition of biomass, (iii) conversion mechanisms and processes, (iv) designing catalyst materials with higher durability and recyclability, (v) greener solvent systems for catalysis and extraction, (vi) the deployment of modern technologies for characterization, (vii) training and guidelines for industrial operations, and (viii) governmental financing and policy. The sustainable manufacturing of biobased products from raw feedstocks produced from biomass has been made possible via technological breakthroughs in photo-/biorefineries, which are essential for the clean and environmentally friendly synthesis of organic acids. It is anticipated that clean production of organic acids from biomass will have a dominant market share, benefiting from both socioeconomic and environmental factors. With future technical developments, the valorization of feedstocks obtained from biomass together with CO₂ for manufacturing fuels and fine chemicals will be more ecologically and economically feasible.

Grafting organophosphonic acids (PAs) on metal oxides has shown to be a flexible technology to tune the surface properties of metal oxides for various applications. The solvents applied in the commonly used synthesis method have associated impeding effect on tailoring the resulting modification degree. In this work, an alternative solid-phase manual grinding method is proposed that (i) is straightforward, (ii) can achieve controllable and higher modification degree, and (iii) excludes the use of solvent during the synthesis. Specifically, propylphosphonic acid (3PA) was grafted onto titania by manual grinding, and different modification degrees were obtained by varying the duration of the post-synthetic thermal treatment. Importantly, the solid-phase method can achieve a modification degree that is 25.0% higher than the maximal modification degree reached by the liquid-phase method, while its atom utilization efficiency is 4.8 times (toluene-based) or 7.5 times (water-based) that of the liquid-phase method.