Insight into the efficient loading and enhanced activity of enzymes immobilized on functionalized UiO-66.

Enzyme immobilization is an effective strategy for achieving efficient and sustainable enzyme catalysis. As a kind of promising enzyme-loading materials, the systematic research on zirconium based metal organic frameworks (Zr-MOFs) about immobilization performance at molecular level is still in its initial stage. In this work, UiO-66 was functionalized with various groups (-H, -NH, -COOH, -OH, -2OH) for the immobilization of cytochrome c (Cyt c) and antioxidant enzyme catalase (CAT). Then the effects of surface-functionalized UiO-66 derivatives on the loading efficiency, enzyme stability and catalysis kinetics were systematically investigated. In addition, the affinity constants of Cyt c and CAT towards UiO-66-series MOFs carriers were also compared. The results have shown that hydroxyl group functionalized UiO-66 represents the highest enzyme loading capacity, enhanced activity and improved stability for Cyt c and CAT possibly due to high surface area and suitable microenvironments as well as enhanced affinity towards the enzymes provided by the introduction of a single hydroxyl group. Our research would foresee immense potential of MOFs in engineering biocatalysts.