Tailored magnetic ZIF-67-derived FeCo-LDH for PETase immobilization toward effective removal and biodegradation of high-crystallinity micro- and nano-PET.

To address the persistent environmental challenge posed by highly crystalline micro- and nano-PET (MP/NPs) pollution, a robust strategy was proposed for their synergistic removal and enzymatic degradation. This approach utilizes tailored magnetic zeolitic imidazolate framework-67 (ZIF-67)-derived FeCo layered double hydroxide (FeCo-LDH) as an immobilization platform for the engineered polyethylene terephthalate hydrolase (PETase) variant ICCG (F-C). The composites were functionalized with tannic acid (TA) and sodium alginate (SA) to achieve improved F-C loading and significantly improve MP/NPs removal efficiency. Comprehensive characterization confirmed successful structural transformation, increased pore size, and favorable magnetic responsiveness. Compared to the free F-C, the immobilized F-C-particularly in TA-modified composites-exhibited significantly enhanced alkaline pH tolerance, thermal stability, and reusability. Most notably, under simulated seawater conditions, the F-C@TA@FeCo-LDH achieved specific activity of up to 50.89 IU/mg and 46.19 IU/mg for highly crystalline (crystallinity degree, Xc = 50 %) NPs and MPs within 96 h, nearly 16 folds that of free F-C. This demonstrates a magnetically recoverable biocatalyst system with strong potential for sustainable MP/NPs removal and degradation under mild conditions.