Cooperative action from Cu-centered MOF and a laccase for enhanced decolorization of synthetic dyes

Laccases are highly versatile copper-dependent enzymes that can oxidize a broad range of substrates, with the combination of converting molecular oxygen to water. However, extreme conditions cause laccase instability, inactivation, and difficulty in its applications. Applying nanomaterials to natural laccase immobilization is essential for their applications as it allows their stabilization and easy recovery from the liquid reaction media and subsequent reuse. Here, we develop an ingenious method to cooperate the copper centers of a copper-based metal-organic framework (Cu-MOF) and a newly discovered laccase-LfLAC3 for effective decolorization of synthetic dyes. The immobilized enzyme presents excellent properties: the catalytic activity improved 62.6-fold, and the half-life (t1/2) at 60 °C increased more than 3-fold, indicating enhanced stability. The reusability was tested by monitoring the decolorization efficiency towards malachite green at 30°C and 60 °C, which demonstrated that the immobilized LfLAC3 can be reused more than ten cycles with more than 80 % removal at both temperatures through a simple centrifugation process. In addition, the detoxification of dyes after enzymatic treatment was also investigated by toxicity assessment. The structural characterization results indicated that copper centers of Cu-MOFs were evenly distributed in MOF-enzyme composites, affording synergistic effects for the catalytic functions. Our work highlights the potential of cooperating metal centers of MOFs and metal enzymes to generate catalysts with promising catalytic properties.