Optimizing polylactic acid alcoholysis efficiency with POM@MOF catalysis

The rapid increase in PLA product consumption has led to significant environmental challenges. To address this issue, this study focuses on developing efficient catalysts to accelerate PLA alcoholysis, aiming to enhance degradation efficiency. A novel composite catalyst, SiWMn Ⅲ @MIL-125(Ti), was synthesized by encapsulating Keggin-type polyoxometalate (POM) in the octahedral cavities of MOF(MIL-125(Ti)). The compound was comprehensively characterized, while density functional theory (DFT) calculations further confirmed the potential localization of POM within the MOF. The catalyst exhibited excellent efficiency in the alcoholysis of polylactic acid (PLA) using ethylene glycol (EG) under optimum conditions (1 wt% catalyst, 160 °C, 30 min, EG/PLA molar ratio = 4:1, 18 % POM loading), achieving high PLA conversion. The liquid products were systematically analyzed, proposing their oligomeric structures. Notably, this heterogeneous catalyst could be easily retained by filtration and could be reused for more than 10 cycles without significant activity loss. Combined with DFT simulations, a reasonable catalytic mechanism was elucidated, highlighting the synergistic role of POM@MOF in facilitating alcoholysis of PLA. This work not only provides insights into the design of efficient MOF-based catalysts for polymer degradation but also suggests the potential applicability of POM@MOF systems in other depolymerization processes.