Solar-Driven Upcycling of Plastic Waste Using Plasmonic Black Gold

Abstract

Plastic waste accumulation poses a pressing environmental challenge, calling for sustainable routes to convert it into value-added products under mild conditions. Conventional Lewis acid-mediated upcycling relies on hydride transfer and carbocation formation but requires ionic liquids to stabilize intermediates and sacrificial alkylating agents like isopentane to overcome thermodynamic barriers. Here, we present a solar-driven, sacrificial-agent-free approach for catalytic plastic upcycling using plasmonic black gold nanostructures. Under visible-to-NIR irradiation, black gold activates tert-butyl chloride (TBC) through combined photothermal and hot-electron driven activation, generating reactive carbocations in polymer chains while converting Al2Cl6 into catalytically active AlCl3 in-situ. This dual activation eliminates the need for ionic liquids and isopentane, enhancing both efficiency and sustainability. The system achieves >80% plastic conversion within one hour solely by light illumination with >85% selectivity toward branched C6-C10 alkanes. Mechanistic studies confirm that plasmonic excitation promotes TBC dissociation and sustains AlCl3 generation throughout the catalytic cycle. The catalyst exhibits excellent recyclability over multiple cycles without loss of activity or selectivity. A proof-of-concept outdoor experiment under natural sunlight further validates its real-world applicability. This work represents unique demonstration of plastic upcycling powered solely by sunlight using a plasmonic catalyst, merging broadband light harvesting, hot-carrier chemistry, and Lewis acid catalysis into a unified, sustainable platform for decentralised upcycling of plastic waste.