Fluorine is an essential element that supports modern society. It is used widely in pharmaceuticals, agrochemicals, electronic materials, and polymeric resins, such as fluoroplastics. The exceptional strength of the carbon-fluorine (C-F) bond, arising from small size and high electronegativity of fluorine, has played a crucial role in enhancing the performance and durability of functional materials. At the same time, however, this extraordinary chemical stability has given rise to significant challenges, including resistance to degradation and accumulation in the environment, which have emerged as serious environmental risks. In recent years, the establishment of innovative technologies for the recycling and circular utilization of fluorine resources through "molecular transformation," rather than simple disposal, has become an urgent global issue. This is due to increasingly stringent regulations on per- and polyfluoroalkyl substances (PFAS) and growing international consensus toward the phased elimination of hydrofluorocarbons (HFCs) with high global warming potentials.

Against this background, Professor Norio Shibata has developed a unique research program that extends far beyond conventional synthesis of organofluorine compounds. By embracing the unconventional concepts of "bond cleavage," "transformation," and "decomposition," he has pioneered a new research field founded on a paradigm shift in fluorine chemistry. In particular, he has addressed the long-standing and unexplored challenge of how to fundamentally control C-F bonds and transform fluorine from just a "functional element" into a "recyclable resource." Through this work, he has established a new academic framework termed "circular molecular transformation technology." The major achievements of Professor Shibata are outlined below.

1. Asymmetric Molecular Transformations Enabled by C-F Bond Cleavage
Professor Shibata was the first to develop asymmetric molecular transformations driven by the formation of silicon-fluorine (Si-F) bonds. By exploiting intramolecular reaction design and the exceptionally high bond dissociation energy of the Si-F bond, he achieved selective and highly stereocontrolled monodefluorination of substrates bearing two strong C(sp³)-F bonds under transition-metal-free conditions. Furthermore, by combining this strategy with SN2′-type reactions, he realized asymmetric construction of C-CF₃ bonds concomitant with C-F bond cleavage. These studies overturned the prevailing assumption that C-F bond cleavage is inherently incompatible with asymmetric synthesis and provided new design principles in which fluorine removal and stereochemical control are seamlessly integrated.

2. Selective Activation of Difluoromethylene Units and Divergent Molecular Transformations
Difluoromethylene (CF₂) units have long been regarded as chemically inert. Professor Shibata challenged this paradigm by precisely combining strong Lewis acids, such as B(C₆F₅)₃ and aluminum-based Lewis acids, with carefully optimized solvent environments. This strategy enabled fine control over mono- or difluorine elimination and carbocation generation at CF₂ centers. As a result, a fluorinated substrate could be divergently converted into cyclized, defluorinated, or functionalized products. This work established the concept of skeletal editing of fluorinated molecules and significantly expanded the design space of organofluorine chemistry.

3. Cooperative C-F Bond Activation Using R₃SiBpin and Potassium Bases
Professor Shibata discovered a cooperative system composed of R₃SiBpin and potassium bases that enables cleavage of both aromatic and aliphatic C-F bonds under metal-free conditions at room temperature. Mechanistic studies revealed that this transformation proceeds through a unique frustrated ion pair/radical pair pathway, in which silyl anion and radical processes operate cooperatively. Beyond C-Si bond formation, the reaction was extended to the construction of C-C, C-O, and C-N bonds. Importantly, the liberated fluorine is quantitatively captured as potassium fluoride (KF), directly linking reaction design with fluorine resource recovery. Density functional theory (DFT) calculations provided detailed mechanistic insight, underscoring the rational basis of this chemistry.

4. Towards a Fluoro-Circular Economy: Decomposition, Upcycling, and Resource Recovery of PFAS and Fluorocarbons
Building on his fundamental studies of C-F bond activation as indicated above, Professor Shibata has addressed one of the most formidable challenges in contemporary fluorine chemistry: the decomposition, upcycling, and resource recovery of PFAS, fluoropolymers, and fluorocarbon gases. Rather than treating these chemically persistent substances as waste, his research redefines them as recyclable feedstocks within a fluoro-circular economy based on molecular-level transformation.

Using mechanochemical approaches, Professor Shibata demonstrated that high-molecular-weight PFAS such as polytetrafluoroethylene (PTFE) and poly(vinylidene fluoride) (PVDF) can be efficiently decomposed at room temperature, enabling the high-yield recovery of KF. Importantly, the resulting "KF black" was shown to act directly as a highly active fluorinating reagent for organic synthesis, thereby directly linking fluoropolymer degradation with value-added chemical production. In parallel, single-electron-transfer-driven decomposition strategies employing sodium dispersions were developed, allowing representative PFAS, including PTFE, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), to be quantitatively converted into sodium fluoride (NaF) under mild conditions. These studies collectively established an upcycling model that directly connects fluoropolymer degradation with synthetic fluorine chemistry.

Extending this circular concept to fluorocarbon gases, Professor Shibata pioneered the controlled generation of reactive fluorinated anions such as CF₃⁻ and C₂F₅⁻ from regulated hydrofluorocarbons including HFC-23 and HFC-125, enabling their direct utilization in the construction of pharmaceutical and agrochemical frameworks. Furthermore, he achieved the quantitative formation of tetrafluoroethylene (TFE) from HFC-125 at room temperature and demonstrated its use as a monomer for the resynthesis of PTFE. This achievement represents the first experimental realization of a closed-loop fluorine resource cycle spanning "fluorocarbon → monomer → polymer."

In addition to reagent-driven approaches, Professor Shibata developed a distinct strategy for PFAS degradation by exploiting ultrahigh electric fields and superacidic environments at water microdroplet interfaces. These interfacial conditions enable one-electron transfer and selective C-F bond cleavage under catalyst-free and reagent-free ambient conditions, leading to the concept of "self-induced decomposition." This approach further expands the conceptual framework of the fluoro-circular economy by integrating natural interfacial phenomena with molecular reaction design.

A defining feature of this body of work is its strong mechanistic foundation. Through the combined use of DFT calculations and advanced spectroscopic analyses, Professor Shibata elucidated the σ* orbital characteristics of C-F bonds, bond dissociation pathways, and single-electron transfer behavior at the molecular level. This comprehensive understanding elevated fluorine recycling and degradation chemistry from an empirically driven practice to a rational and predictive science, firmly anchoring fluoro-circular technologies in fundamental chemical principles.

Concluding Remarks
Through original reaction design grounded in a fundamental understanding of C-F bond chemistry, Professor Norio Shibata has transformed organofluorine chemistry from a discipline centered on synthesis into a science of circular resources. His achievements have made profound contributions to organic synthesis, environmental chemistry, and resource science, while simultaneously addressing pressing global challenges related to sustainability. These accomplishments fully justify his recognition as a highly deserving recipient of the Chemical Society of Japan Award.