The Brønsted-Lewis acid sites in Metal-organic framework nanozymes for cooperatively enhancing the hydrolysis of lactose

Abstract

Abstract 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 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 theoretical support for the design of MOFs nanozymes.