Hematin and Cu control generations of hydroperoxyl and superoxide radicals to activate galactose oxidase for 5-hydroxymethylfurfural conversion.

We present a significant finding that Cu(II) ions can activate hematin (Hem) to generate more HOO⋅ and O radicals from the decomposition of HO. Galactose oxidase (GO) and hematin have been simultaneously immobilized by coordinating to Cu(II) ions (GO&Hem@Cu(II)). The radicals HOO⋅ and O and dioxygen O can be generated from the byproduct HO by the Cu(II)-activated hematin. Ample experimental evidence supports the discovery that the immobilized GO is reactivated by the generated HOO⋅ and O. For the conversion of 100 mM 5-hydroxymethylfurfural (HMF) in water, GO&Hem@Cu(II) (0.8 mg/mL GO encapsulated) has achieved a 99.5% conversion within 180 min. In contrast, 0.8 mg/mL free GO M variant (ACS Catalysis 2018, 8, 4025) has achieved an HMF conversion of 17.3%. For the conversion of HMF (1,000 mM) by GO&Hem@Cu(II) (4 mg/mL GO encapsulated), the HMF conversion is 98.8% after 8 h reaction.