Ionic liquid modulation of metal-organic framework immobilized laccase and boosted its catalytic performance for organic pollutants removal

Although Metal-organic frameworks (MOF) are a series of excellent carriers in the immobilization of laccase, excessive interaction can also lead to the denaturation and inactivation of laccase, which limited their further industrial application. In this study, ionic liquids were applied as a series of novel modifiers of metal-organic framework (ILs-NH2-MIL-101) in the immobilization of laccase. The results showed that the loading amounts and activity retention were significantly enhanced to 1.6 and 1.4 times respectively, compared with traditional laccase NH2-MIL-101. The stability and catalytic activity of the enzyme were also significantly improved. Moreover, the application of our novel-designed laccase-ILs-MIL-101 in removing organic pollutants was also examined in this study and found that the removing efficiency of 50 mg/L of 2,4-dichlorophenol, 4-chlorophenol, bisphenol A and indole, etc, can reach 95.4%, 91.4%, 90.3%, and 89.8%, respectively. The molecular dynamic simulations (MD) studies suggested that the immobilized laccase had a better rigid structure and stronger hydrogen bonding interactions with the substrate compared with free laccase, which facilitated the stability of the laccase and the degradation efficiency of the substrate. Therefore, this study proposed a simple, practical, and low-cost strategy based on ILs for the modification of various MOFs, which provides new insights into the development of high-efficiency enzyme immobilization for various industrial productions.