The Brønsted-Lewis Acid Sites in Metal–Organic Framework Biomimetic Nanozyme for Cooperatively Enhancing the Hydrolysis of Lactose

In order to solve the problem of the low efficiency of lactose hydrolysis using traditional metal–organic frameworks (MOFs) nanozymes, Brønsted acid active sites (-COOH) were firstly introduced into Fe-MIL-101 nanozymes to enhance the lactose hydrolysis activity of MOFs bearing Lewis acid sites in this study. When compared to Fe-MIL-101, Fe-MIL-101-COOH exhibited improved catalytic performance, showing a lactose conversion rate of up to 78%. Our experiments suggested that this enhancement could be attributed to the synergistic effect between the Brønsted acidic COOH groups and Lewis acidic Fe clusters. Furthermore, Fe-MIL-101-COOH displayed good stability and reusability with no significant loss in catalytic activity observed after at least five consecutive cycles. Our results showed that the activity of Fe-MIL-101-COOH with Brønsted acid active sites was better than that of Fe-MIL-101. Fe-MIL-101-COOH could be applied to the hydrolysis of lactose in milk powder and the conversion rate of lactose was higher than 48%. This study provided support for the application of MOFs nanozymes in lactose catalytic conversion.