Selective Degradation of Styrene‐Related Plastics Catalyzed by Iron under Visible Light**

Abstract

Efficient degradation of plastics, the vital challenge for a sustainable future, stands in need of better chemical recycling procedures that help produce commercially valuable small molecules and redefine plastic waste as a rich source of chemical feedstock. However, the corresponding chemical recycling methods, while being generally restricted to polar polymers, need improvement. Particularly, degradation of chemically inert nonpolar polymers, the major constitutes of plastics, suffers from low selectivity and very harsh trans-formation conditions. Herein, an efficient method was developed for selective degradation of styrene-related plastics under gentle conditions through multiple oxidation of sp 3 CÀ H bonds and sp 3 CÀ C bonds. The procedure was catalyzed with inexpensive iron salts under visible light, using oxygen as green oxidant. Furthermore, simple iron salts could be used to degrade plastics in the absence of solvent under natural conditions, highlighting the potential application of iron salts as additives for degradable plastics.

Catalytic oxidation of polystyrene to aromatic oxygenates over a graphitic carbon nitride catalyst

“…In addition, the element analysis of recovered polystyrene confirmed that a small content of oxygen was introduced into the polystyrenes (Supplementary Table 4 ). These findings demonstrated that our heterogonous catalytic transformation process of polystyrene is different from traditional pyrolysis 8 , 47 and oxidation 29 , 31 reaction routes of polymers, where random C–C bonds were cleaved to produce microplastics or oligomers. Instead, the spectroscopic result together with gel permeation chromatography (GPC) and liquid product analysis clearly indicated that partial oxidation of polystyrene by reactive oxygen species occurred in the induction period of reaction.…”

“…Previous works have exhibited that polystyrene can be selectively converted into the monomer styrene 24 or other arenes such as benzene 25 by heterogeneous catalysts, while the upgradation into functionalized aromatics with higher value was mainly achieved by homogeneous catalysts 26 . Very recently, oxidative deconstruction of polystyrene was reported, which depolymerized and transformed the polymer into high-value products with oxygen-containing groups, such as benzoic acid [27][28][29][30][31] . The photocatalytic benzylic C-H bond activation was involved in most of these catalytic processes.…”

Visible-Light-Induced Iron Group Metal Catalysis: Recent Developments in Organic Synthesis

“…The system was found to enable the depolymerization of PS under natural conditions in the absence of solvents, showing the potential of using iron salts for degradable plastics. 24b Subsequently, Stache and Oh showed the scalability of the iron system to depolymerize PS into mixed small molecules, such as benzaldehyde, benzoic acid, and benzoyl chloride, through flow chemistry. 24c…”

Light-mediated aerobic oxidation of C(sp3)–H bonds by a Ce(iv) hexachloride complex

“…[21][22][23][24][25][26] Recently, Cl • has been studied extensively and employed in alkylarene oxygenation reactions. Recently, Hu, Jiang and Zeng employed iron catalysts; [27][28][29] Wang's group used HCl as a catalyst and Shi and co-workers disclosed cerium photoredox catalysis 30 during the final stages of the investigations presented herein. However, the substrate scope of these systems was rather restricted and was generally limited to alkyl aromatics.…”