Sustainable Closed-Loop Recycling of Polyester Waste Using Reconstructed Defective-Metal-Organic Frameworks

Chemical recycling of polyester waste presents a promising strategy for achieving a sustainable circular economy. However, the development of efficient, low-cost recycling methods that minimize energy consumption and carbon emissions remains challenging. Here, we report an approach for depolymerization polyester waste to bis(hydroxyethyl)terephthalate (BHET) using a reconstructed metal-organic framework (r-Zn-MOF74-NT) catalyst under mild conditions. The r-Zn-MOF74-NT exhibited a space-time yield of 1035.8 g_BHET g_cat ^-1 h^-1 at 190 °C. Importantly, this is an order of magnitude higher than that reported for similar MOF-based catalysts. In situ spectroscopy combined with theoretical calculations revealed that the depolymerization pathway involves the activation of oxygen and ethylene glycol adsorbed on r-Zn-MOF74-NT, forming nucleophilic intermediates. These intermediates then facilitate the cleavage of the polyester C─O bond through nucleophilic attack, thereby gradually generating the BHET product. Sustainability evaluation results validated the circular economy feasibility of the recycling approach, with a minimum sales price (MSP) of 498 $/ton, much lower than the MSP of the traditional petroleum-based production route (1000 $/ton). The approach also achieved a 61% reduction in energy use and a 52% decrease in greenhouse gas emissions. This work provides a sustainable solution for managing polyester waste accumulation.