Studies on Immobilization and Activity of Peroxidase Based on Zr-based MOFs

Abstract Metal-Organic Frameworks (MOFs) are a kind of porous crystalline compounds, which are self-assembled by metal clusters and organic ligands through coordination bonds. UiO66 is a kind of MOF crystal materials with a porous octahedral structure, which is coordinated by zirconium ion and terephthalic acid (H2BDC). In this paper, UiO66-NH2 and UiO66-(COOH)2 were prepared, and UiO66-NH2 was modified by Post-Synthetic Modification (PSM) to obtain UiO66-NH2-COOH material. The prepared samples and intermediate products were characterized by infrared spectrum (IR). UiO66-NH2-COOH and UiO66-(COOH)2 materials were loaded with horseradish peroxidase (HRP), which catalyzed the reaction between H2O2 and 3, 3', 5, 5'-tetramethylbenzidine (TMB). Via the results of UV-vis spectrophotometry measurement, it was found that UiO66-(COOH)2 loaded with HRP had better catalytic effects than only HRP. In order to verify the influence of carboxyl groups on UiO66-NH2-COOH and UiO66-(COOH)2 materials, the adsorption of rhodamine B (RhB) was studied in this paper. The results of fluorescence spectrophotometer showed that UiO66-NH2-COOH material had better adsorption effect on RhB than UiO66-(COOH)2 material, which may be attributed to the flexibility of UiO66-NH2-COOH material after PSM. UiO66-NH2-COOH and UiO66-(COOH)2 materials were characterized by X-ray powder diffraction (XRD) before and after adsorption of RhB. The XRD pattern of UiO66-(COOH)2 material has no obvious characteristic peak, which indicates that it belongs to nanoparticle polymer. The results are consistent with the UV-visible results, and the nanoparticle polymer has better catalytic effects.