Sustainable Synthesis of Biomass-Derived C8 Monomers for Closed-Loop Recyclable and Biodegradable Polyesters

Fully biomass-based plastics with closed-loop recyclability and biodegradability are pivotal for sustainable polymer development. However, their synthesis remains challenging, primarily due to the limited availability of suitable monomers. Here, we report a novel approach for sustainable synthesis of suberic acid, a key C8 <i>α</i>,<i>ω</i>-dicarboxylic acid, achieving a high yield of 85.5% from biomass-derived 2-formyl-5-furancarboxylic and malonic acids, via sequential Knoevenagel condensation and hydrodeoxygenation catalyzed by Pd/HZSM-5 and MoO_<i>x</i>/TiO₂. Subsequent hydrogenation of suberic acid on CoO_<i>x</i> yielded two additional C8 monomers, 8-hydroxyoctanoic acid and 1,8-octanediol, in high yields of 89.5 and 92.8%, respectively. These monomers enabled the synthesis of poly(8-hydroxyoctanoate) (PHO) and poly(octylene suberate) (POS) via melt polycondensation. The two polyesters exhibited excellent thermal and mechanical properties, comparable to low-density polyethylene. PHO displayed superior toughness to commercial materials and retained this toughness at low temperatures (e.g., -20 °C). Crucially, both polyesters demonstrated outstanding closed-loop chemical recyclability (with polymer-to-polymer recycling rates of ∼95%) and biodegradability (with mineralization rates of ∼87%). This work establishes a viable strategy for synthesizing long-chain <i>α</i>,<i>ω</i>-dicarboxylic acids from renewable feedstocks, advancing the design of high-performance polyesters with full life-cycle sustainability.