Hooked for Decay with Hydrophobic-Coated Magnetic Beads to Grapple and Disintegrate Nanoplastics

Degradation of synthetic polymers inevitably leads to the formation of nanoplastics (NPs), and recent studies associate health risks with NPs. Therefore, catching and degrading NPs are important to manage environmental and human health risks. In this study, we developed a biohybrid catalyst system with two functionalities to capture (Hook) and degrade (Decay) NPs. The biohybrid catalyst is composed of a Grubbs-Hoveyda (GH) type cofactor conjugated to the material-binding peptide LCI_F16C, which immobilizes the GH-cofactor onto superparamagnetic iron oxide nanoparticles (SPIONs). The anchored biohybrid catalyst initiates a ring-opening metathesis polymerization to generate a hydrophobic polynorbornene film around iron oxide core, which enables to efficiently capture and remove a broad spectrum of hydrophobic NPs, including polypropylene, polyethylene, polystyrene (PS), poly(ethylene terephthalate), poly(methyl methacrylate), and styrene-butadiene rubber (SBR), with hydrophobic interaction as the main driving force. This hydrophobic coating facilitated rapid adsorption of PS-COOH_{500 nm} NPs within 10 min, reaching an impressive adsorption capacity of 5.53 ± 0.29 g/g on PS NPs, and demonstrated a high recovery efficiency of 99% for SBR NPs. Notably, the embedded GH-cofactor preserved its ethenolysis activity, cleaving internal C═C bonds of SBR and resulting in 6.5% degradation, thereby validating the concept of simultaneous nanoplastic capture and catalytic breakdown.