Interface-Designed Relay Hydrogenation-Hydrogenolysis over Base-Metal Catalysts Enables Stereochemically Controlled Upcycling of Waste PET to CHDM

The catalytic upcycling of poly(ethylene terephthalate) (PET) into monomer-grade diols with controlled stereochemistry remains challenging because of polymer inertness, limited stereocontrol in downstream hydrogenation, and the reliance on precious-metal catalysts under forcing conditions. Here, we report a relay hydrogenation-hydrogenolysis strategy enabled by interface-designed base-metal catalysts for the one-pot conversion of PET into 1,4-cyclohexanedimethanol (CHDM) with a trans-enriched stereochemical profile. An inverse ZrO2/Ni catalyst efficiently promotes aromatic-ring hydrogenation by enhancing H2 activation while moderating aromatic adsorption, achieving near-complete hydrogenation of PET under mild conditions. Subsequently, a m-ZnO/Cu catalyst selectively facilitates ester hydrogenolysis, affording CHDM in yields up to ∼86% with trans/cis ratio exceeding 3.60 in the one-pot system. Mechanistic studies reveal that CHDM stereoselectivity does not originate from ester bond cleavage itself but emerges from stage-dependent catalytic regulation and is strongly influenced by the evolving reaction environment, particularly ethylene glycol generated in situ during hydrogenolysis. Validation using real post-consumer PET feedstocks—including bottles, films, food containers, and mulch films—demonstrates consistently high CHDM yields (73−79%) with trans-enriched stereochemistry. Catalyst-recycling experiments confirm stable performance over multiple cycles after appropriate regeneration. Furthermore, techno-economic and life cycle assessments indicate that this PET upcycling route reduces the carbon footprint of CHDM production by approximately 3.6-fold compared with conventional naphtha-based processes. This work establishes interface-designed base-metal catalysis as a viable platform for the stereochemically controlled and responsible upcycling of waste polyesters.