Hydrolyzable Bio‐Based Bisphenols Enabled by the Tishchenko Reaction for Polyurethane Vitrimers with Closed‐Loop Recyclability

Polyurethane (PU) is a cornerstone of modern materials science, yet its reliance on petroleum-based precursors and the limited recyclability of conventional formulations pose significant environmental challenges. In this study, a fully bio-based polyurethane vitrimer system is developed enabled by a dual-function SmI₂-mediated strategy that integrates Tishchenko coupling and phenol deprotection in a single step, simplifying the synthesis of bio-based bisphenols with 100% atom utilization. These bisphenols introduce hydrolyzable ester bonds, allowing for complete degradation within ≈3 d (representative model), providing an efficient and eco-friendly end-of-life solution. This approach offers a sustainable alternative to conventional bisphenol A (BPA). Moreover, by leveraging the electronic effects of bio-based bisphenols, the dissociation temperature of phenol-carbamate bonds can be widely tuned (≈70-120 °C), endowing the resulting Covalent Adaptable Network (CAN) PUs with excellent reprocessability, closed-loop recyclability, and reconfigurable shape memory capability. Furthermore, the aromatic and ester-rich structure enhances thermomechanical performance, yielding tensile strengths up to 33 MPa, elongations at break exceeding 400%, and toughness reaching 30 MJ m^- ³, surpassing most sustainable PUs. This work pioneers a scalable and fully bio-based PU vitrimer platform with tunable performance, recyclability, and sustainable degradability, offering a compelling alternative to traditional thermosets and thermoplastics for next-generation green materials.