Fostering Global Networks for Green and Sustainable Chemistry

New circular polymeric materials for a carbon-neutral future must be designed to operate within a circular economy framework. Traditionally, polymers have relied on irreversible covalent bonds between repeating monomer units, which limits their recyclability. Recently, however, increasing attention has been directed toward dynamic polymers constructed from reversible covalent or non-covalent bonds, enabling reuse and recycling.
Dynamic polymers contain reversible linkages that can be formed from monomers and cleaved back into monomeric units by external stimuli such as heat or light. Among these, 2π+2π cycloaddition reactions represent a particularly promising class of reversible reactions. Only a limited number of molecular systems, including cinnamate, stilbene, thymine, coumarin, and styrylpyrene derivatives, are known to undergo such reactions.
In the first part of this study, we systematically validate the potential of these reversible reactions through topochemically controlled monomer-to-polymer transformations based on 2π+2π cycloaddition. These approaches enable the creation of functional circular polymers, such as self-healing materials and reusable adhesives.
In the second part, we report the synthesis of novel circular polymers derived from lignin. Glycerol-based polyfunctional monomers bearing cinnamate groups were prepared via a sustainable process using vanillin and syringaldehyde, which are readily obtained from lignin oxidation. These monomers were employed to fabricate bio-based, photo-crosslinkable and decrosslinkable circular polymers. Circular polymers derived from other bio-based compounds, such as soybean oil, are also presented.
Finally, we introduce newly developed environmental assessment tools to evaluate the environmental performance of these materials. In particular, we have extended the conventional E-factor concept to explicitly incorporate product circularity, enabling a more comprehensive and practical assessment of material sustainability. In addition, we briefly introduce the activities of our Circular Materials Centre, which focuses on close collaboration with industrial partners in Japan to accelerate the practical implementation of circular polymer technologies.

Chemical recycling of waste plastics into naphtha-range hydrocarbons is a promising route toward a circular carbon economy. Zeolite-catalyzed degradation enables selective formation of light hydrocarbons suitable for existing naphtha crackers; however, post-consumer plastics contain inorganic additives that may deactivate catalysts. The effects of such additives under realistic recycling conditions remain poorly understood.

Here, we investigate the impact of inorganic additives in real polyolefin wastes on zeolite-catalyzed degradation in a hydrocarbon solvent, focusing on calcium carbonate and talc. Catalytic degradation experiments were carried out in a batch reactor using a hydrocarbon solvent to ensure sufficient fluidity of molten plastics and effective contact with the catalyst. Typically, 5 g of plastic sample and 20 g of solvent were charged into the reactor together with 0.25 g of an acid-type Beta zeolite catalyst. For comparison, thermal degradation experiments were conducted under identical conditions without the catalyst.

After purging the reactor with nitrogen, the system was heated at a rate of 10 ^oC min^-1 to 400 ^oC and maintained at this temperature for 60 min. Upon completion of the reaction, the reactor was cooled to room temperature. Gaseous products were collected, and the liquid and solid phases were separated by filtration. Polymer conversion was determined gravimetrically from the remaining solid residue. Additives were identified by XRD and ICP-OES, product distributions were analyzed by GC-FID, and catalyst acidity was evaluated by NH₃-TPD.

Calcium carbonate–containing plastics wastes showed a strong suppression of naphtha-range (C₃–C₉) oning via Ca²⁺ leaching and ion exchange with zeolite acid sites. In contrast, talc-containing plastics exhibited only minor reductions in light hydrocarbon yields, and the zeolite retained its acidity, suggesting that Mg species in talc remain structurally stable and do not participate in ion exchange.
These results demonstrate that inorganic additives exert highly additive-specific effects on zeolite-catalyzed chemical recycling. Avoiding catalyst-poisoning fillers such as calcium carbonate, or replacing them with benign mineral additives like talc, is crucial for efficient and selective plastic chemical recycling from a green chemistry perspective.

The ongoing depletion of fossil fuel resources has spurred intense interest in alternative carbon-based energy and material sources, including biomass, CO₂, and waste polymers, in both industrial and academic communities. Substantial efforts have therefore been devoted to biotechnology and sustainable or green technologies aimed at establishing a chemical industry in which renewable carbon resources complement diminishing fossil fuel feedstocks. These renewable resources are typically found in highly oxidized and/or oxygen-rich forms. Consequently, conventional oxidation catalysis must be fundamentally re-envisioned to enable efficient reduction and dehydration processes suitable for their chemical valorization. In this lecture, I will present the (PNNP)Ir complex as a unified and versatile catalytic platform for the reductive upgrading of biomass-derived carboxylic acid derivatives¹ and CO₂,² as well as for the reductive upcycling of polyesters.³
(1) Saito, S. et al. Sci. Adv. 2020, 6, eabc0274; ACS Catal. 2022, 12, 1957.
(2) Saito, S. et al. J. Am. Chem. Soc. 2020, 142, 10261; Chem. Commun. 2022, 58, 9218;
Inorg. Chem. 2023, 62, 14116; Chem. Eur. J. (Concept), 2025, e202500328.
(3) Saito, S. et al. Research Square (Preprint), 2026, DOI: 10.21203/rs.3.rs-8409046/v1.

The increasing demand for lithium-ion batteries has intensified supply risks associated with nickel and cobalt, motivating recycling strategies that reduce reliance on these critical metals while retaining cathode functionality. This study demonstrates a direct upcycling route that converts spent LiNi_0.6Mn_0.2Co_0.2O₂ (NMC622) cathodes into next-generation Li-rich, high Mn content, layered oxides (LMR), following the general formula of Li_1+x(Mn, Ni, Co)_1–xO₂. Spent NMC622 was first recovered from Samsung cells, combined with Li and Mn salts, and subsequently processed via solid-state synthesis. X-ray diffraction confirmed the expected mixed-phase structure, which was indexed to hexagonal (R-3m) and monoclinic (C2/m, Li₂MnO₃-like) domains. LMR delivered initial discharge capacities of 260 mAh g^-1. Partial oxygen substitution with fluorine increased the first-cycle LMR capacity to 289 mAh g^-1 and reduced the first-cycle loss. At 20 mA g^-1, the upcycled fluorine-containing LMR exhibited improved voltage stabilization and reduced polarization compared to the F-free counterpart. Overall, this work demonstrates a direct cathode upcycling strategy, which switches dependence from costly Ni (in NMC622) to a cheap Mn-based next generation lithium ion cathode material. This lowers critical metal demand and supports resource-efficient circular battery economies that will aid ongoing green energy transitions.

Snakebite envenomation is a neglected tropical disease with a substantial public health burden, particularly in Africa and Asia. Among venom components, phospholipase A2 (PLA2) enzymes play a central role in venom-induced tissue damage and inflammation. In this study, we report a non-animal, sustainability-aligned workflow for evaluating the antisnake venom potential of the methanol extract of Cissus repanda using enzyme-based in vitro assays, HR-LCMS-guided metabolomic profiling, and in silico analysis. The methanol extract was assessed for inhibitory activity against PLA2 enzymes from Naja nigricollis and Echis ocellatus venoms using an in vitro acidimetric assay, avoiding the use of animal models and reducing biological resource burden. The extract demonstrated significant PLA2 inhibition, with maximum and minimum inhibition values of 85.4% and 42.7% at concentrations of 1.25 and 10.0 mg/mL, respectively. High-resolution liquid chromatography–mass spectrometry (HR-LCMS) enabled efficient identification of eleven putative bioactive metabolites. To further minimize experimental redundancy and chemical waste, these compounds were prioritized using molecular docking, yielding binding affinities ranging from −6.8 to −5.2 kcal/mol. Three compounds with the most favorable binding poses were selected for post-docking analyses, and in silico ADMET evaluation to assess pharmacokinetic and safety-related properties. This integrated approach demonstrated how HR-LCMS-guided metabolomics and computational screening can reduce solvent use, experimental waste, and ethical burden in natural product–based antivenom research. The findings support Cissus repanda as a promising renewable source of antisnake venom leads and highlight a green chemistry–oriented framework for sustainable bioactive compound discovery

In recent years, manufacturing sites in Japan have faced significant changes driven by a declining labor population, increased automation, and growing environmental requirements based on ESG and SDGs initiatives. As a result, cutting fluids are now expected not only to provide high machining performance and long tool life, but also to contribute to improved workplace conditions and reduced operating costs. In particular, water-soluble cutting fluids often present challenges such as microbial degradation, unpleasant odors, and sticky residues, as well as increased running costs caused by higher concentrate consumption and waste fluid disposal.
This presentation reports the development concept and performance evaluation of a newly developed water-soluble cutting fluid, the Daphne Alphacool NV Series, which was designed from a new perspective of suppressing the consumption of active components and maintaining a favorable coolant cycle over extended periods. The NV Series is based on two core technologies: (1) reduction of coolant carry-off through the formation of a dense adsorption film on metal surfaces using specially designed fatty acids, and (2) improved thermal stability and pH retention achieved by employing low-volatility amines. These technologies aim to simultaneously extend coolant service life, reduce concentrate replenishment, and suppress odor and sticky residue formation.
Evaluation results obtained from a customer survey of 100 users and from actual machining lines covering non-ferrous metals, steels, alloy steels, stainless steels, and cast irons demonstrated that the NV Series significantly improves environmental performance and cost efficiency. In addition, stable machining performance comparable to or superior to conventional water-soluble cutting fluids was confirmed across a wide range of machining operations, including high-load processes. These results indicate that the NV Series is an effective solution for achieving a balance among environmental improvement, cost reduction, and machining performance in modern manufacturing environments.