Heterogeneous iron-doped covalent triazine framework for the efficient photocatalytic upcycling of polystyrene waste to valuable aromatics under ambient conditions

Polystyrene (PS), a widely used commodity plastic, has a persistently low recycling rate, making it a major contributor to plastic pollution. Selective PS upcycling under ambient conditions remains challenging due to its chemically inert structure, characterized by stable C C and C H bonds. As a consequence, efficient PS degradation typically requires energy-intensive pyrolysis or harsh oxidizing conditions. Existing homogeneous photocatalysts, such as strong acids or metal salts, are unsustainable long-term solutions for PS waste management due to their lack of reusability and complex separation requirements. Although covalent organic frameworks (COFs) and covalent triazine frameworks (CTFs) have previously been explored as general photocatalysts, their use in selective PS upcycling remains underexplored. Here, we report an iron-doped CTF for the efficient photocatalytic upcycling of PS under ambient conditions. By harnessing the framework's porous character and tunable electronic and photophysical properties, the catalyst incorporates less than 3 wt% iron and offers a sustainable alternative to photocatalysts with higher metal content. Synthesized via solvent-free mechanochemical Friedel-Crafts alkylation of trichlorotriazine and phenothiazine, the CTF forms a porous, p -type semiconductor with FeCl 4 − ions cross-linking 2D CTF polymer sheets to form an [FeCl 4 ]@CTF heterogeneous photocatalyst. The disclosed [FeCl 4 ]@CTF photocatalyst achieves 100% degradation of commercial and post-consumer PS under ambient conditions, yielding approximately 70% of valuable aromatic compounds with high selectivity. The scalable mechanochemical synthesis of the CTF, coupled with its reduced reliance on high metal loadings provides a sustainable blueprint for organocatalyst-driven plastic waste management using earth-abundant metals. A covalent triazine framework (CTF) is prepared via a sustainable mechanochemical route and subsequently modified by low-level Fe doping to enhance its photocatalytic properties. The resulting heterogeneous photocatalyst completely degrades post-consumer polystyrene waste under ambient conditions, selectively converting it to commercially valuable aromatic products with high yields. • Scalable mechanochemical synthesis of a covalent triazine framework (CTF), followed by simple post-synthetic Fe doping to generate a heterogeneous photocatalyst • The heterogeneous Fe-doped CTF photocatalyst upcycles polystyrene (PS) waste under ambient conditions, with complete PS degradation and ~ 70% yield of commercially valuable aromatics • Very low Fe content (<3 wt%) with negligible metal leaching and stable catalytic activity over repeated cycles • Given the amorphous nature of the CTF, solid-state NMR, X-ray absorption spectroscopy, transient absorption spectroscopy and density functional theory were used to elucidate the catalyst structure and reaction mechanism