Design And Application Of Nanozymes Based On Metal-organic Frameworks

Nanomaterials with natural enzyme catalytic activity are collectively referred to as nanozymes.Compared with natural enzymes,nanozymes have the advantages of high stability,low price and easy preparation,and show good potential in applications in various fields,and are considered to be an ideal alternative to natural enzymes.Although more and more nanomaterials are reported to exhibit enzyme-like activities,the research of nanozymes still confronts many challenges.On the one hand,compared with the natural enzymes,nanozymes have lower catalytic efficiency and catalyze fewer types of reactions.On the other hand,nanozymes are poorly specific,and one material commonly has multiple enzyme-like activities at the same time.These problems severely limit the application of nanozymes.Therefore,the design and development of structurally well-defined nanozymes with high activity and specificity and the study of their applications in practice have become the focus of research.Metal organic frameworks（MOFs）are porous coordination polymers composed of metal cluster nodes and organic ligands connected by regular linkage.MOFs materials have the advantages of well-defined structure,high specific surface area,regular pore channels and excellent biocompatibility.The nanozymes based on MOFs materials have a wide range of applications in various fields such as antibacterial,analytical detection,cancer therapy and environmental protection.In this thesis,a series of MOFs-derived nanozymes were designed and synthesized to explore the feasibility of rational design for active sites in improving the selectivity and activity of nanozymes,as well as their applications in pollutant degradation and antibacterial fields.The details are as follows.1.Oxidase-like MOF-818 nanozyme with high specificity for catalysis of catechol oxidation.The nanomaterial MOF-818 was prepared by mimicking the active site of natural catechol oxidase.It was shown that the synthesized MOF-818has a higher catalytic activity than the natural enzyme and can efficiently catalyze the oxidation of catechol and its derivatives and produce hydrogen peroxide.Unlike the already reported catechol-like oxidases,MOF-818 is highly specific,catalyzes the oxidation of catechols selectively and does not possess POD-like activity.2.Diatomic Fe-Fe catalyst enhances the ability to degrade organic contaminants by nonradical peroxymonosulfate activation system.Fe₁-N-C,Fe₂-N-C,and Fe₃-N-C catalysts with dispersed mono-,di-and tri-iron active centers were synthesized were synthesized by one-step carbonization using easily prepared ZIF-8 as a sacrificial template and loading different kinds of iron-containing salts in ZIF-8 precursors.Their catalytic oxidative degradation activities of Rh B,BPA and 2,4-DP were studied.Benefiting from the unique coordination environment of Fe₂N₆,Fe₂-N-C exhibited the highest degradation activity.EPR experiments have shown that a variety of ROS are generated during catalytic degradation.Free radical quenching experiments further proved that Fe（IV）and singlet oxygen played a major role in catalyzing the degradation of contaminants.3.HKUST-1/GO as a nanozyme exhibits antioxidant and antibacterial functions simultaneously.The composite material HKUST-1/GO was formed by combining the HKUST-1 with GO in a one-step hydrothermal method.It has multiple enzymatic activities such as catalase-like,superoxide-like and glutathione peroxidase-like activities,and is capable of scavenging reactive oxygen species such as hydrogen peroxide,hydroxyl radicals and superoxide radicals.At the same time,it is also a highly effective wide spectrum antibacterial agent with efficient antibacterial activity against both gram-negative and gram-positive bacteria under alkaline conditions.By combining antioxidant and antimicrobial strategies,HKUST-1/GO possesses both efficient antioxidant and bactericidal abilities and has promising applications in the treatment of injuries and chronic ailments.