Advanced Catalytic Strategies for Plastic Depolymerization: Mechanistic Insights, Catalyst Engineering, and Sustainable Upcycling Pathways

The exponential rise in plastic production and consumption has resulted in the accumulation of persistent polymeric waste, posing severe environmental and ecological challenges. Global plastic generation exceeds 400 million tonnes annually, with dominant materials including polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), and polystyrene (PS). Advanced catalytic depolymerization has emerged as a sustainable strategy to convert plastic waste into valuable monomers, fuels, and chemical intermediates. This review provides a comprehensive and expanded analysis of catalytic depolymerization approaches, including homogeneous, heterogeneous, biocatalytic, photocatalytic, and pyrocatalytic methods. Mechanistic pathways, catalyst design strategies, and reaction optimization are discussed in detail. The role of nanostructured materials, metal–organic frameworks (MOFs), enzyme engineering, and hybrid catalytic systems is critically evaluated. Emerging technologies such as plasma-assisted catalysis and electrocatalysis are also explored for their potential in energy-efficient plastic valorization. The integration of these catalytic technologies is essential for advancing circular economy models and mitigating global plastic pollution.