Selective Consecutive Decarboxylation Enables Skeletal Contraction of Waste PET.

Direct catalytic upcycling of waste polyethylene terephthalate (PET) to benzene through consecutive decarboxylation contracts the terephthalate-derived C8 framework to C6, representing a skeletal-editing strategy for aromatic polycarboxylates. The key challenge is to control pathway selection across consecutive decarboxylation steps, favoring sequential aryl-carboxyl C-C bond cleavage over competing hydrogenolysis while preserving the aromatic core. Herein, we report an efficient direct catalytic conversion of waste PET to benzene, achieving an exceptionally high yield of 83.3% over a tailored Ru/W0.4ZrOx catalyst. The performance arises from synergistic acid-site reconstruction and oxygen-vacancy engineering. Moderate WOx incorporation into ZrO2 converts Lewis acidity into Brønsted acidity, while oxygen vacancies and WOx species promote adsorption and activation of carboxyl groups. In cooperation with Ru nanoparticles, these features preferentially stabilize the decarboxylation intermediate over its hydrogenolysis counterpart, directing both consecutive steps toward C-C bond cleavage while suppressing undesired hydrogenolysis pathways. Controlled hydrogen supply and a deliberately designed dodecane/water mixed solvent system further enhance selectivity. The catalyst performs effectively across diverse real-world PET wastes, with preliminary techno-economic and life-cycle analyses indicating favorable process-level metrics under the evaluated assumptions. More broadly, these mechanistic insights establish synergistic acidity and oxygen-vacancy regulation as a catalyst-design principle for decarboxylative skeletal editing of aromatic polycarboxylates.