Towards Bio‐Based Benzoxazines (2015–2025): A Critical Review of Renewable Building Blocks, Formaldehyde‐Free Aldehydes, and ECHA Hazard Landscape

This review provides a critical overview of research on fully bio‐based benzoxazines over the period 2015–2025. A bibliometric analysis based on the Web of Science database is used to map how the field has evolved and to identify the renewable building blocks that have been most widely adopted. The objective of this study is to discuss the utilization of various bio‐based phenols—including cardanol, vanillin, eugenol, guaiacol, diphenolic acid, ferulic acid, thymol, and chavicol—and amines—such as furfurylamine, stearylamine, and dehydroabietylamine—as building blocks for this emerging class of sustainable thermosets. Furthermore, the study examines the aldehydes proposed as replacements for formaldehydes, in particular, hydroxymethylfurfural (HMF) and glyoxal, and quantifies the extent to which they have actually been taken up in benzoxazine synthesis. A comparative risk analysis based on European Chemicals Agency (ECHA) classifications is included to evaluate the hazard profiles of aldehyde precursors currently employed, highlighting the need for safer and more sustainable alternatives. The challenges and opportunities associated with the use of different bio‐based feedstocks are discussed, along with recent developments in synthetic methodologies—including the use of greener solvents, solvent‐free processes, and alternative energy sources such as microwave‐assisted synthesis. The bibliometric analysis shows that the way this literature is retrieved determines what is found. Searching the self‐declared term “fully bio‐based” returns 82 publications for 2015–2025 and suggests a field in decline after 2019, whereas retrieval based on the precursors actually employed—a renewable phenol combined with a renewable amine—returns 140 publications and reveals sustained growth, from 2 publications in 2015 to 22 in 2025, an increase in share from 0.9% to 5.7% of all benzoxazine output. Within this corpus, the substitution of petrochemical precursors has advanced very unevenly: furfurylamine overtook aniline as the most frequently reported amine in 2021 and had nearly doubled it by 2025, while on the aldehyde side paraformaldehyde use grew by 150% over the same period, and glyoxal and hydroxymethylfurfural together account for 4 of 520 aldehyde occurrences (0.8%). The formaldehyde‐free transition has therefore been proposed but not adopted, and this gap between the sustainability rationale and synthetic practice is the central finding of this review.