Immobilization of Laccase by Alkali-Etched Bimetallic CoCu-MOF To Enhance Enzyme Loading and Congo Red Degradation

In this work, the strategy of immobilizing enzymes in bimetallic-organic frameworks was adopted to overcome the disadvantages of free laccases. The surface amino-silanizing of bimetallic CoCu-MOF-H hydrothermally synthesized was performed by (3-Aminopropyl)triethoxysilane (APTES). Then, glutaraldehyde was used as the cross-linking agent, laccase was covalently grafted onto CoCu-MOF-H-APTES to prepare Lac-CoCu-MOF-H-APTE. In addition, CoCu-MOF-OH also was synthesized by alkali etching of CoCu-MOF-H, and Lac-CoCu-MOF-OH-APTES composites were obtained by a similar strategy. The result showed that the relative enzyme activity of Lac-CoCu-MOF-OH-APTES exhibited 264.02% (1.8 times than that of Lac-CoCu-MOF-H-APTES) after six cycles of stability tests, while the free enzyme was almost inactivated. Moreover, the Congo red (CR) removal rate of Lac-CoCu-MOF-OH-APTES exceeded 95% within 1 h and exceeded 89.18% after six cycles at pH 3.5 and 50 °C. This work has the potential to provide a broader application prospect for CR degradation by laccase in the future.