Catalyst-free, microdroplet-mediated waste plastic conversion to diacids.

Abstract

Plastic waste accumulation poses a global threat to both the environment and public health^1-3. Although catalytic upcycling to value-added chemicals holds promise, its industrial adoption is hindered by additive-induced catalyst deactivation, feedstock heterogeneity, process inflexibility and limited economic viability⁴. Here we report a catalyst-free upcycling strategy that makes use of in situ generation of hydroxyl radicals at microdroplet interfaces^5-8 to enable oxidative cleavage of diverse waste plastics-from polyolefins to rubbers-into carboxylic acids under mild conditions. By eliminating catalyst-dependent pathways, this approach circumvents key challenges of catalyst design and poisoning, while substantially lowering technical barriers and costs^9,10. Our method achieves complete conversion of polyethylene (PE) with selectivity to short-chain diacids approaching 69% under relatively mild conditions and demonstrated broad applicability to mixed commercial plastics, with scalability demonstrated up to the 300-g scale. Radical intermediate analysis reveals the crucial role of H₂O in mediating a unique oxidative degradation mechanism: sequential hydroxyl radical addition to alkyl radicals, distinct from classical liquid-phase aerobic oxidation of alkane¹¹. This interfacial radical-mediated strategy enables sustainable polymer upcycling with minimal infrastructure. More broadly, this work provides a scalable blueprint for the first, to our knowledge, industrial implementation of microdroplet chemistry, with transformative implications for oxidation processes in organic acid synthesis and beyond.