Polyolefins, such as polyethylene (PE) and polypropylene (PP), dominate modern plastic production due to their low cost

and durability, driving widespread single-use consumption and contributing to a global waste crisis. Despite advances in

mechanical recycling, most polyolefin waste—over 85%—is still landfilled or incinerated, and mechanical processes often

degrade polymer properties, resulting in material downcycling. In contrast, catalytic upcycling offers a more sustainable

route to convert polyolefin waste into fuels and chemical feedstocks. However, conventional catalytic processes, such as

hydrogenolysis and hydrocracking, require high-pressure fossil-derived hydrogen, raising concerns over carbon emissions and

process sustainability. This review highlights recent advances in hydrogen-free catalytic strategies for polyolefin upcycling,

covering both thermocatalytic and electrified approaches. We discuss pyrolysis over solid acids at elevated temperatures;

solvent-assisted systems where solvents donate hydrogen and influence degradation pathways; metal–acid catalysts that

utilize hydrogen released from the polymer itself; and oxidative upcycling routes using O2 and CO2 as reactants for selective

oxygenation and aromatization. The mechanistic roles of metal and acid sites, hydrogen transfer pathways, and confinement

effects are analyzed to clarify how product selectivity and reaction efficiency are controlled. By comparing these diverse

strategies, this review identifies key design principles for hydrogen-free polyolefin valorization and outlines future research

directions toward circular, low-carbon plastic waste management.