Poly(3-hydroxyalkanoates) (PHA), promising biodegradable polymers, are hindered by the lack of efficient catalytic systems for competitive commercialization. Addressing this, we introduce a chloro-bridged dimeric salphen zirconium cobaltate complex. Under mild conditions under base-free conditions, it achieves full monomer conversion, 92% PHA selectivity, and challenges the prevailing β-lactone pathway. Instead, direct epoxide and carbon monoxide co-polymerization emerges as a unique and efficient PHA synthesis mechanism

Comprehensive Summary

Poly(3-hydroxyalkanoates) (PHAs) are a promising class of biodegradable polymers, exhibiting properties comparable to traditional petroleum-based counterparts. Nonetheless, the widespread commercialization of PHAs is hindered by the absence of an efficient and economically viable catalytic system, impeding their competitiveness against non-biodegradable polymers. In an effort to address this challenge, we present a study on a newly developed chloro-bridged dimeric salphen zirconium cobaltate complex for the direct synthesis of PHAs via carbonylative polymerization of epoxides. The catalytic system demonstrates favorable activity under mild reaction conditions, enabling complete monomer conversion and an impressive 92% selectivity towards PHA formation. Through meticulous control experiments and mechanistic studies, we have gained crucial insights into the polymerization process. Remarkably, our findings challenge the prevailing notion of sequential ring-opening polymerization of in-situ generated β-lactones as the primary pathway. Instead, we demonstrate that the polymerization predominantly proceeds through direct co-polymerization of epoxide and carbon monoxide, unveiling a unique and efficient mechanism for PHA synthesis.