Materials from green resources boast a low carbon footprint, forming the foundation of the circular economy approach in materials science. Thus, in this study, waste poly(ethylene terephthalate) (PET) was subjected to depolymerization using propylene glycol (PG), and subsequent polycondensation with bio-based maleic anhydride (MA) produced unsaturated polyester resin (b-UPR). Bio-derived acryloyl-modified Kraft lignin (KfL-A) served as a vinyl reactive filler in the b-UPR matrix to create b-UPR/KfL-A composites. The structural characterization of KfL-A and b-UPR involved the use of FTIR and NMR techniques. The mechanical properties of the newly fabricated composites were assessed through tensile strength, Vickers microhardness, and dynamic mechanical tests. The addition of KfL-A to the rigid b-UPR matrix enhanced material flexibility, resulting in less stiff and hard materials while preserving composite toughness. For instance, incorporating 10 wt% of KfL-A in b-UPR led to a 17% reduction in hardness, a 48% decrease in tensile strength, and a 20% reduction in toughness. Positive environmental impact was achieved by incorporation of 64 wt% of renewable and recycled raw material. Analogously prepared b-UPR/KfL composites showed structural inhomogeneity and somewhat better mechanical properties. Transmission (TEM) and scanning (SEM) electron microscopies revealed a suitable relationship between mechanical and structural properties of composites in relation to the extent of KfL-A addition. The UL94V flammability rating confirmed that flame resistance increased proportionally with the KfL-A addition. Once deposited in a landfill, these composites are expected to disintegrate more easily than PET, causing less harm to the environment and contributing to sustainability in the plastics cycle.

A versatile synthesis strategy for fluorescent 3-halo-4H-chromen-4-one derivatives is reported. The method involves the oxidative α-halogenation of enaminones performed by an efficient and sustainable oxidation system. The use of Oxone® in combination with KCl, KBr, or KI enables the preparation of 3-chloro-, 3-bromo-, or 3-iodo-4H-chromen-4-one in good to excellent yields, with great functional group tolerance where the protocol is amenable to gram-scale synthesis. The analysis of the photophysical properties of the presented 4H-chromen-4-one showed absorption in the UV region and fluorescence emission in the violet-to-cyan region with a relatively large Stokes shift. In solution, all compounds present a dual fluorescence emission, regardless of the solvent, assigned to a partially aromatised intramolecular charge transfer mechanism, considering the presence of a pseudo-aromatic ring in the chromone scaffold and the absence of the influence of substituent electronic features in optical behaviour.

Over the past century, a substantial amount of research focused on developing corrosion inhibitors, with a special focus on green \"plant-based\" corrosion inhibitors. Among the various types of inhibitors, polyphenols emerged as a promising candidate due to their advantageous characteristics, which include being inexpensive, biodegradable, renewable, and, most importantly, safe for both the environment and humans. Their performance as sustainable corrosion inhibitors have encouraged many electrochemical experiments as well as theoretical, mechanistic, and computational studies, with many papers reporting inhibition efficiencies of over 85%. In this review, the majority of literature contributions on the inhibition of various types of polyphenols, their natural extraction techniques, and their applications as \"greener\" corrosion inhibitors for metals are thoroughly described and discussed with a focus on their preparation, inhibition mechanism, and performance. Based on the reviewed literature, it can be concluded that polyphenols have a very promising potential to be used as both green and powerful corrosion inhibitors; therefore, further investigations, experimental or computational, are still required to realize higher inhibition efficiencies reaching up to ≈ 100%.

Biocatalysis has the potential to enable green chemistry. New methods of enzyme immobilisation will be required to improve enzyme stability, product purification, and compatibility of different enzymes in the same reaction conditions. Deoxyribonucleic acid (DNA) stands out among supramolecular scaffolds, as simple Watson-Crick base-pairing rules can be used to rationally design a unique nanoscale environment around each individual enzyme in a cascade. Enhancements of enzyme activity and stability on DNA nanostructures have previously been reported, but never in the context of industrially relevant chemical syntheses or reaction conditions. Here, the authors show DNA can enhance the activity and stability of a galactose oxidase mutant, which could be used in a cascade to produce bioplastics from lignin. The enzyme was enhanced in the cell-free extract, which to their knowledge has not been shown before for any enzymes on DNA. This is significant because crude biocatalytic reactions are vastly more cost-effective. This opens the door to further work on multienzyme cascades by tuning the properties of individual enzymes.

Although the concepts underpinning green chemistry have evolved over the past 30 years, the practice of green chemistry must move beyond the environmental and human health-related roots of green chemistry towards a more systems-based, life cycle-informed, and interdisciplinary practice of chemistry. To make a transition from green to sustainable chemistry, one must learn to think at a systems level; otherwise green chemistry-inspired solutions are unlikely to be sustainable. This perspective provides a brief description of why the current situation needs to change and is followed by how life cycle thinking helps chemists avoid significant systems-level impacts. The transition from batch to continuous flow processing and novel approaches to isolation and purification provide a case for interdisciplinary collaboration. Finally, an example of end-of-useful-life considerations makes the case that systems and life cycle thinking from an interdisciplinary perspective needs to inform the design of new chemical entities and their associated processes.

Due to the negative effects of emerging contaminants on the environment, that can potentially induce deleterious effects in aquatic and human life, this paper focuses on the removal from the water of Furosemide, through the adsorption process. Indeed, only a few papers are available in the literature about the Furosemide adsorption and, chitosan films are thus proposed for this purpose as safe, sustainable, and recyclable adsorbent materials. In the present work, the effects on the adsorption process of several experimental parameters such as the pH values, ionic strength, amount of adsorbent/pollutant, and temperature values were investigated. The kinetics models, isotherms of adsorption, and the thermodynamic parameters were studied showing that the Furosemide physisorption occurred on the heterogeneous Chitosan surface, endothermically (ΔH° = +31.27 ± 3.40 kJ mol-1) and spontaneously (ΔS° = +150.00 ± 10.00 J mol-1 K-1), following a pseudo-second-order kinetic model. The 90% of the pollutant was adsorbed in 2 h, with a maximum adsorption capacity of 3.5 mg × g-1. Despite these relatively low adsorption capacities, experiments of desorption were performed and 100% of adsorbed Furosemide was recovered by using concentrated NaCl solutions, proposing a low-cost and green approach, with respect to the previous literature relative to the Furosemide adsorption, fundamental for the pollutant recovery and adsorbent reuse.

This paper describes a sustainability index (SI) as a quantitative measure of \"sustainability\" applicable to synthesis plans based on the provenance of input materials and energy sources and the fate of output waste products. The index is computed as the root-mean-square average of the following four parameters: mass fraction of valorized inputs (F VI ), mass fraction of valorized outputs (F VO ), mass fraction of valorized target product (F VP ), and input enthalpic energy fraction arising from renewable energy sources (F RE ). Valorized input materials originate from renewable, recycled, or reclaimed sources. Valorized output materials are destined for recycling or reclaiming so that they may be used in the same or other chemical processes. Valorized target product refers to that portion of the target product that is actually used for its intended purpose. Renewable energy sources are defined as originating from hydroelectric, wind, solar, geothermal, and biomass sources. The computation of SI is illustrated for 22 synthesis plans of the high commodity flavour ingredient vanillin from biofermentation, chemical synthesis, and solvent extraction processes. In addition, these plans are compared and ranked according to Borda count and poset (partially ordered set) pairwise dominance analyses using the following attributes: process mass intensity (PMI), sacrificial reagent (SR) consumption, input enthalpic energy (IEE) consumption, Rowan solvent greenness index (RSGI), and sustainability index (SI).

In recent years, the advancement of sustainable chemistry concepts and approaches along with their demonstrated application has become a central part of the design, synthesis, and manufacture of a chemical. Sustainable chemistry not only utilizes the principles of green chemistry, but also expands to incorporate economic, societal, and environmental aspects. This is further elucidated by the incorporation of life cycle assessment/thinking to include the raw material production, manufacture, processing, and use and disposal stages, allowing for a comprehensive evaluation of the environmental and human health impacts attributed to a chemical. This contribution outlines an approach for the development of a preliminary framework for the sustainable synthesis of a chemical that is identified as an alternative for an existing chemical of concern. The framework is introduced concurrently with a case study for organophosphates that are selected as potential replacements for brominated flame retardants (BFRs). This framework is designed to apply existing knowledge of green chemistry to the synthesis of alternatives, along with its integration into Life Cycle Assessment culminating in the development of a more overall sustainable chemical entity when compared to its predecessor.

For the reaction mechanism of the ketonic decarboxylation of two carboxylic acids, a β-keto acid is favored as key intermediate in many experimental and theoretical studies. Hydrogen atoms in the α-position are an indispensable requirement for the substrates to react by following this mechanism. However, isolated observations with tertiary carboxylic acids are not consistent with it and these are revisited and discussed herein. The experimental results obtained with pivalic acid indicate that the ketonic decarboxylation does not occur with this substrate. Instead, it is consumed in alternative reactions such as disintegration into isobutene, carbon monoxide, and water (retro-Koch reaction). In addition, the carboxylic acid is isomerized or loses carbon atoms, which converts the tertiary carboxylic acid into carboxylic acids bearing α-proton atoms. Hence, the latter are suitable to react through the β-keto acid pathway. A second substrate, 2,2,5,5-tetramethyladipic acid, reacted by following the same retro-Koch pathway. The primary product was the monocarboxylic acid 2,2,5-trimethyl-4-hexenoic acid (and its double bond isomer), which might be further transformed into a cyclic enone or a lactone. The ketonic decarboxylation product, 2,2,5,5-tetramethylcyclopentanone was observed in traces (<0.2 % yield). Therefore, it can be concluded that the observed experimental results further support the proposed mechanism for the ketonic decarboxylation via the β-keto acid intermediate.

In the context of recycling metal to embrace the sustainability challenge, this work proposes a geochemically-analogous process of metal recovery through mechanochemistry for the first time, to avoid the limitations of on-going methods and to establish an innovative technology philosophy. This work systematically investigates this geochemically-analogous process, to keep it green and to generalize it further. Copper recovery from waste printed circuit boards (WPCBs), a typical copper-rich waste, is chosen as a case study in this work. Nearly 98% of the copper in the WPCBs can be recycled in the optimized conditions and 82.3% of the sulfur can be reused, by means of the process. Based on the experimental result, this paper purports a closed-loop route of copper recovery which follows the green chemistry principles (high yield, high atom economy and no secondary pollution). This route can be generalized into other second-hand resources that are rich in copper. Some other metals (e.g. lead) that are commonly present as corresponding sulfides in nature can be taken into consideration in this geochemically-analogous process as well.