Co-immobilization of laccase and PEG modified COFs into Cu doped gel beads to achieve synergistic effect of photocatalysis and enzymatic catalysis for pollutants removal

In this work, PEG modified photocatalytic covalent organic framework (PEG@CTF-OMe) was co-immobilized with laccase into Cu doping calcium alginate gel beads (Ca/Cu-PEG@CTF-OMe-lac). PEG@CTF-OMe improved the light stability of laccase under blue light irradiation, and external introduction of copper into gel beads stabilized the conformation and improved pH adaptability of laccase. With the help of 2,2-binamine-di-3-ethylbenzothiazolin-6-sulfonic acid (ABTs), the immobilized laccase (Ca/Cu-PEG@CTF-OMe-lac) presented outstanding synergistic removal of pollutants by photocatalysis and enzymatic catalysis, as well as ABTs radicals generation promoting by copper ions in the laccase-mediator system. The removal recyclability performance assay found that the Ca/Cu-PEG@CTF-OMe-lac gel beads had more than 80 % removal efficiency for phenol, 4-chlorophenol, 2,4-dichlorophenol, nonyl phenol, bisphenol A and indole in water at 25 °C after 5 cycles, when the concentration reached as high as 70 mg/L, 60 mg/L, 120 mg/L, 100 mg/L, 100 mg/L and 100 mg/L, respectively. The high synergistic removal performance obtained by the gel beads co-immobilizing laccase and photocatalytic CTFs showed greater practical application value.