Encapsulation of Carbon-Nanodots into Metal-Organic Frameworks for Boosting Photocatalytic Upcycling of Polyvinyl Chloride Plastic

Abstract

Although polyvinyl chloride (PVC) ranks as the third most mass-produced synthetic plastic, the chemical upcycling of non-biodegradable PVC waste remains a significant challenge. Herein, novel carbon nanodots (CDs)-embedded metal-organic framework (MOF) that CDs/Zr-MOF photocatalyst is fabricated for upcycling of PVC. Specifically, the ultra-small-sized CDs (~2.0 nm) are encapsulated into Zr-MOF pores via a mild pyrolysis strategy. The maintained MOF structure facilitates charge/mass transfer and improves the surface-to-volume ratio of active sites of CDs. The CDs/Zr-MOF exhibits high activity for PVC conversion of ~76.5% towards acetic acid with a yield of ~14%. The mechanism investigation indicates the generated •OH radicals can efficiently trigger cleavage of C-Cl/C-C bonds of PVC. Moreover, the reduction of the energy barrier for the hydroxylation reaction as a rate-limiting step contributed to improved PVC conversion performance. This work offers a feasible method for fabricating nanoparticle-embedded MOF-based photocatalysts and provides new insights into the chemical upcycling of plastics.

Keywords: polyvinyl chloride, mild pyrolysis, CDs/Zr-MOF photocatalyst, acetic acid