Green Chemistry最新文献

The present study offers a metal-free photocatalytic visible-light-driven protocol for addressing the plastic waste crisis. The reaction uses photocatalytic C–H bond activation to deconstruct polystyrene (PS) waste into valuable products under ambient conditions (1 bar O₂, 250 W Hg lamp) in an ethyl acetate/acetonitrile solvent system. The high surface area metal-free photocatalyst was synthesised using flow-assisted exfoliation and demonstrated high selectivity for acetophenone and PS conversion in sunlight. The study presents a promising and sustainable approach to combat plastic pollution by introducing the concept of visible light photocatalysis for polymer deconstruction. The technology offers a simple, reproducible, eco-friendly method that could significantly contribute to a circular economy to produce wealth (chemicals) from waste. Detailed characterisations, control experiments, and scavenging studies have been conducted to propose the mechanism of PS upcycling to acetophenone and benzoic acid. The photocatalytic C–H activation showcased in this study could motivate material scientists and catalysis researchers to create uncomplicated, metal-free photocatalysts that can activate other bonds with high dissociation energy, leading to the formation of crucial synthetic intermediates of industrial significance. This technology represents a crucial step towards more efficient and sustainable methods for combatting plastic pollution, highlighting the potential of green chemistry for creating sustainable solutions to environmental challenges.

Polyethylene terephthalate (PET), as the most widely utilized polyester, causes global environmental problems due to its massive and durable accumulation in natural environments. The glycolysis of PET is an attractive alternative to mechanical recycling, but there remains a strong demand for efficient, convenient, and inexpensive catalysts. Herein, we present a spray-drying-assisted way to construct magnetic hollow micro-sized nanoaggregates (HMNAs) by assembling composite metal oxide nanoparticles to depolymerize PET synergistically. The as-prepared ZnO–Fe₃O₄ HMNAs completely depolymerized PET with a high monomer yield of 92.3% in a short period of 30 min at 190 °C, far above individual ZnO and Fe₃O₄ nanoparticles (NPs). The composite HMNAs can be magnetically separated in a few minutes and maintain a high activity for 5 cycles. DFT study reveals that the HMNAs effectively facilitated glycolysis by the high content of Lewis acid sites as well as the stronger adsorption between PET and the catalyst owing to the structural synergy effect of ZnO–Fe₃O₄ HMNAs. Furthermore, this spray drying strategy as a versatile and scalable methodology is extended to fabricate other HMNAs, exhibiting a similarly enhanced efficiency of glycolysis. The HMNAs are expected to open up avenues for the design of catalysts for upcycling of discarded plastics.

The use of sunlight to initiate free radical polymerization under air is a key challenge. Due to the associated low light intensity, usual or commercial photoinitiators are characterized by a low efficiency. In this work, seventeen carbazole-fused coumarin-based oxime esters were developed as monocomponent and photocleavable (Type I) initiators of polymerization displaying excellent light absorption properties in the visible range. Compared to the benchmark photoinitiator (diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide), some of them (namely OXE-1 and OXE-5) could show photoinitiation performance similar to or better than the reference compound upon irradiation with a LED at 405 nm. The photoinitiation mechanism of these photoinitiators is proposed, supported by theoretical calculations; the detection of CO₂ during photopolymerization was performed by means of Fourier transform infrared spectroscopy and the detection of radical species was performed by electron spin resonance analysis. Through direct laser writing, different objects exhibiting an excellent spatial resolution could be obtained. Parallel to the photoinitiating ability, the different photoinitiators also showed a thermal initiation behavior, meaning that these structures can serve both as thermal and photo-initiators on demand. Due to the high sensitivity of these structures to sunlight, OXE-1 and OXE-5 were also investigated as solar photoinitiators (reactive also in Central Europe during winter) and excellent monomer conversions could be obtained within one hour using a multifunctional acrylate monomer (Ebecryl 605). To the best of our knowledge, these two oxime esters constitute the first examples of sunlight activable oxime esters ever reported in the literature.

A convenient method for synthesizing aryl-containing trisubstituted alkenes through direct alkylation of alkenes was successfully achieved under solvent-free and catalyst-free conditions. The absence of solvents was found to be crucial in initiating this sequence. Moreover, this protocol stands out due to its minimal waste production and straightforward operation. The radical capture experiment provided evidence for an ionic reaction mechanism.

When we look for a poster child of green chemistry ‘in action’, we do not need to look further than the deconstruction of lignocellulose using ionic liquids (IL) to valorize this renewable resource into useful chemicals. However, there is a caveat: successful development of new chemistries cannot be achieved without systems-based design tools that consider performance in conjunction with potential toxicity. Here, we show that a combination of computational approaches, based on quantum mechanics (QM) calculations and Monte Carlo (MC) simulations, can be leveraged to construct a useful framework for screening existing and designing new ILs capable of safe and selective dissolution of lignocellulosic biomass. With the overwhelming number of IL cation–anion combinations, in silico methods are uniquely suited for this challenge so long as they retain mechanistic relevance to the underlying processes. Our computational approach ensures this criterion by relying on well-correlated linear models of interaction energetics between IL and key biomass building blocks. Functional considerations are supplemented with frontier molecular orbital calculations to determine safety toward aquatic species based on previously established and broadly validated guidelines.

Solvent toxicity is a major barrier to sustainable fabrication of polymeric membranes. This study introduces three dibasic esters (DBEs) as alternative membrane fabrication solvents that are biodegradable, non-carcinogenic, non-corrosive, and non-hazardous. The use of DBEs in fabrication processes shifts the monotectic point in the phase diagram of PVDF/solvent systems towards higher polymer concentrations, enabling membrane formation by liquid–liquid phase inversion to produce a bicontinuous structure that confers outstanding performance. The best-performing membrane prepared in this way had an exceptional flux of 42.40 kg m⁻² h⁻¹ and a high rejection rate (>99%) in the decontamination of synthetic nuclear wastewater. Compared to membranes prepared previously using toxic and non-toxic solvents, membranes fabricated in DBEs exhibited superior mechanical performance due to their bicontinuous structure, which effectively distributes external forces throughout the membrane. Moreover, DBEs are cheaper than toxic conventional solvents and are readily available in bulk, making them attractive options for industrial-scale membrane production.

Hemoproteins have recently emerged as attractive biocatalysts for catalyzing carbene-mediated cyclopropanation, a synthetically valuable reaction not found in nature. In this study, we present a hemoglobin-catalyzed strategy for the highly stereoselective synthesis of nitrile-substituted cyclopropanes. This method offers efficiency and environmental friendliness by utilizing an asymmetric olefin cyclopropanation reaction catalyzed by wild-type Vitreoscilla hemoglobin in the presence of in situ generated diazoacetonitrile. A diverse range of nitrile-substituted cyclopropanes could be synthesized in water with exceptional stereoselectivity, achieving up to 99.9% de and ee and high turnover numbers of up to 3232. By employing this sustainable approach, not only can various chiral nitrile-substituted cyclopropanes be efficiently obtained, but also the practical application of hemoglobin in organic synthesis can be expanded.

Green and nano-structured catalytic media are vital for biocatalysis to attenuate the denaturation tendency of biocatalysts under severe reaction conditions. Hydrotropes with multi-faceted physiochemical properties represent promising systems for sustainable protein packaging. Herein, the ability of adenosine-5′-triphosphate (ATP) and cholinium salicylate ([Cho][Sal]) ionic liquid (IL) to form nano-structures and to nano-confine Cytochrome c (Cyt c) enhanced the stability and activity under multiple stresses. Experimental and computational analyses were undertaken to explain the nano-structured phenomenon of ATP and IL, structural organizations of nano-confined Cyt c, and site-specific interactions that stabilize the protein structure. Both ATP and IL form nano-structures in aqueous media and could cage Cyt c via multiple nonspecific soft interactions. Remarkably, the engineered molecular nano-cages of ATP (5–10 mM), IL (300 mg mL⁻¹), and ATP + IL surrounding Cyt c resulted in 9-to-72-fold higher peroxidase activity than native Cyt c with exceptionally high thermal tolerance (110 °C). The polar interactions with the cardiolipin binding site of Cyt c, mediated by hydrotropes, were well correlated with the increased peroxidase activity. Furthermore, higher activity trends were observed in the presence of urea, GuHCl, and trypsin without any protein degradation. Specific binding of hydrotropes in highly mobile regions of Cyt c (Ω 40–54 residues) and enhanced H-bonding with Lys and Arg offered excellent stability under extreme conditions. Additionally, ATP effectively counteracted reactive oxygen species (ROS)-induced denaturation of Cyt c, which was enhanced by the [Sal] counterpart of IL. Overall, this study explored the robustness of nano-structured hydrotropes to have a higher potential for protein packaging with improved stability and activity under extreme conditions. Thus, the present work highlights a novel strategy for real-time industrial biocatalysis to protect mitochondrial cells from ROS-instigated apoptosis.

Reported here is the CO₂-facilitated radical sequential (3 + 2) annulation of 1,6-enynes that proceeds under the concerted catalysis of sulfinate and a photocatalyst (PC) to construct benzo-fused tricyclic scaffolds, that is tetrahydrofluorenes and their N-heterocyclic analogues, in generally good yields. This CO₂-facilitated method allows the stable aromatic groups of 1,6-enynes to undergo radical addition-induced dearomatization and rearomatization under metal-, external oxidant- and base-free conditions and features a broad scope of 1,6-enyne substrates, as demonstrated by more than 60 examples including a series of 1,6-enyne derivatives of complex bioactive compounds. Importantly, CO₂ as a green additive is disclosed to be essential for achieving this reaction with good efficiency, demonstrating a new role of CO₂ in this transformation.